lower macdonald river flood study...lower macdonald river flood study webb, mckeown & associates...

HAWKESBURY CITY COUNCIL

LOWER MACDONALD RIVER

FLOOD STUDY

AUGUST 2004

HAWKESBURY CITY COUNCIL

LOWER MACDONALD RIVER FLOOD STUDY

AUGUST 2004

Webb, McKeown & Associates Pty Ltd Prepared by: ___________________________Level 2, 160 Clarence Street, SYDNEY 2000Telephone: (02) 9299 2855Facsimile: (02) 9262 6208 Verified by: ____________________________22032:MacRiverFSFinal.wpd

LOWER MACDONALD RIVER FLOOD STUDY

TABLE OF CONTENTS

PAGE

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Catchment Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 General Morphology and Flood History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.1 Previous Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.2 Topographic and Hydrographic Information . . . . . . . . . . . . . . . . . . . . . . . . . 42.3 Rainfall Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.4 Streamflow Gauging Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.5 Historical Flood Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3. APPROACH ADOPTED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4. HYDROLOGIC MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.1 Hydrologic Model Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.2 Model Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.3 Calibration and Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.3.1 Key Model Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104.3.2 Historical Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5. HYDRAULIC MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135.1 General Approach and Model Establishment . . . . . . . . . . . . . . . . . . . . . . . . 135.2 Hydraulic Model Calibration and Verification . . . . . . . . . . . . . . . . . . . . . . . . 13

5.2.1 March 1978 Event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145.2.2 August 1990 Event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6. DESIGN FLOWS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166.2 Hydrologic Modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166.3 Flood Frequency Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186.4 Adopted Design Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

7. DESIGN FLOOD (HYDRAULIC) MODELLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227.1 Tailwater Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227.2 Design Flood Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

7.2.1 Flood Levels, Extents and Flow Distribution . . . . . . . . . . . . . . . . . 237.2.2 Provisional Flood Hazard and Hydraulic Categorisation . . . . . . . . 257.2.3 Provisional Categorisation of Flood Prone Land . . . . . . . . . . . . . . 26

7.3 Comparison of the 100 Year ARI Design Event With the 1949 Flood . . . . . 27

8. CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

9. ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

10. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

LIST OF APPENDICES

APPENDIX A: GLOSSARY OF FLOOD RELATED TERMSAPPENDIX B: PUBLISHED GEOMORPHOLOGICAL ANALYSIS OF MACDONALD RIVER APPENDIX C: PHOTOGRAPHS OF HISTORICAL FLOOD LEVEL SURVEY SITESAPPENDIX D: DESIGN FLOOD RESULTS

LIST OF TABLES

Table 1: Available Rainfall Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Table 2: Available Streamflow Gauging Stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Table 3: Recorded Flood Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Table 4: WBNM Model Calibration: Adopted Model Parameters . . . . . . . . . 11Table 5: Historical Storms: WBNM Model Performance . . . . . . . . . . . . . . . . . . . . . . 11Table 6: Modelled Peak Flows (m3/s) at St Albans . . . . . . . . . . . . . . . . . . . . . . . . . . 17Table 7: Sensitivity of Initial Loss Values - 100 Year ARI Peak Flow Estimates . . . . 17Table 8: Sensitivity of Areal Reduction Factors - 100 Year ARI Peak Flow Estimates

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Table 9: Annual Flood Series: Macdonald River at St Albans (Station 212010) . . . . 18Table 10: Flood Frequency Analyses: Macdonald River at St Albans (Station 212010)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Table 11: Design Flood Levels at Wisemans Ferry . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Table 12: Summary of Design Flood Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Table 13: 100 Year ARI Event - Provisional Flood Categorisation . . . 27

LIST OF FIGURES

Figure 1: Study AreaFigure 2: Available Survey DataFigure 3: Available Hydrologic DataFigure 4: WBNM Model LayoutFigure 5: Historical Rainfall Data: March 1978 EventFigure 6: Historical Rainfall Data: August 1990 EventFigure 7: Historical Rainfall Data: April 1988 EventFigure 8: Historical Rainfall Data: August 1986 EventFigure 9: Flow Hydrographs: March 1978 EventFigure 10: Flow Hydrographs: August 1990 EventFigure 11: Flow Hydrographs: April 1988 EventFigure 12: Flow Hydrographs: August 1986 EventFigure 13: MIKE11 Model LayoutFigure 14: Comparison with Available Data: March 1978 Event Peak Flood Height ProfileFigure 15: Stage Hydrographs at St Albans: March 1978 Calibration EventFigure 16: Discharge Hydrographs at St Albans: March 1978 Calibration EventFigure 17: Comparison with Available Data: August 1990 Event Peak Flood Height ProfileFigure 18: Stage Hydrographs at St Albans: August 1990 Verification EventFigure 19: Discharge Hydrographs at St Albans: August 1990 Verification EventFigure 20: Flood Frequency AnalysesFigure 21: Peak Height Profiles: Design Events - Macdonald RiverFigure 22: Design Flood Levels: 500 Year ARI EventFigure 23: Design Flood Levels: 200 Year ARI EventFigure 24: Design Flood Levels and Extents: 100 Year ARI EventFigure 25: Design Flood Levels: 50 Year ARI EventFigure 26: Design Flood Levels and Extents: 20 Year ARI EventFigure 27: Design Flood Levels: 10 Year ARI EventFigure 28: Design Flood Levels: 5 Year ARI EventFigure 29: Design Flood Levels and Extents: Extreme Flood EventFigure 30: Example of Flow Distribution at Model Cross-SectionsFigure 31: Flood Hazard at Cross-Sections: 100 Year ARI Flood EventFigure 32: Flood Hazard at Cross-Sections: Extreme Flood EventFigure 33: Categorisation of Flood Prone LandFigure 34: Comparison of 100 Year ARI Design Event With The 1949 Historical Event: Peak

Height Profile - Macdonald RiverFigure C1: Observed Flood Heights - Longitudinal Profile of Macdonald River

Lower MacDonald River Flood Study

Webb, McKeown & Associates Pty Ltd22032:MacRiverFSFinal.wpd:18 August 2004 a

The State Government’s Flood Policy is directed at providing solutions to existing flooding problems

in developed areas and to ensuring that new development is compatible with the flood hazard and

does not create additional flooding problems in other areas.

Under the Policy, the management of flood liable land remains the responsibility of local

government. The State Government subsidises flood mitigation works to alleviate existing

problems and provides specialist technical advice to assist Councils in the discharge of their

floodplain management responsibilities.

The Policy provides for technical and financial support by the Government through the following

four sequential stages:

1. Flood Study

• determines the nature and extent of the flood problem.

2. Floodplain Risk Management Study

• evaluates management options for the floodplain in respect of both existing and

proposed development.

3. Floodplain Risk Management Plan

• involves formal adoption by Council of a plan of management for the floodplain.

4. Implementation of the Plan

• construction of flood mitigation works to protect existing development,

• use of planning controls to ensure new development is compatible with the flood

hazard.

The Macdonald River Flood Study constitutes the first stage of the management process for this

catchment. This study has been prepared for Hawkesbury City Council by Webb, McKeown &

Associates to define flood behaviour under current conditions.


Webb, McKeown & Associates Pty Ltd22032:MacRiverFSFinal.wpd:18 August 2004 i

This report was prepared by Webb McKeown and Associates on behalf of Hawkesbury City Council

(HCC) and details the engineering investigations carried out to determine the design flood levels,

flows and velocities for the Lower Macdonald River floodplain. It represents the first step in the

process to develop a Floodplain Risk Management Plan for the study area.

The Macdonald River catchment is a tributary of the Hawkesbury River and drains an area of

approximately 1845 km2. Significant flooding has occurred in the past including a severe event in

1949.

All available topographic, rainfall and flood data were collected and analysed as part of the study.

To extend the existing data sets, Council undertook detailed survey to provide cross-section

information and to define the heights of historical flood levels provided by local residents.

A WBNM hydrologic model was established to represent the entire catchment draining to the

Hawkesbury River. A MIKE-11 hydraulic model was created to represent the Lower Macdonald

River downstream of the confluence with Womerah Creek. The lower reaches of Wrights Creek

were also included in the hydraulic model.

The hydrologic and hydraulic models were calibrated making best use of available historical data

to ensure that they reasonably simulated recorded historical floods. The models were calibrated

to the March 1978 flood and verified against the August 1990 event. For both models, parameter

values found to be applicable in previous studies of similar catchments and those from established

texts were used to determine appropriate values for the present study.

In addition, a flood frequency analysis was undertaken on the streamflow estimates obtained from

the gauge located on the Macdonald River at St Albans. The adopted set of design flows were

used to define inflow hydrographs to the hydraulic model. The lower reaches of the Macdonald

River are influenced by a combination of flows entering from the upper catchment in addition to

elevated water levels associated with concurrent flooding in the Hawkesbury River. Design flood

information was therefore obtained using the calibrated hydraulic model in conjunction with a range

of tailwater conditions.

The main outcomes of this study are documented in this report and include:

• a full description of the methodology and results,

• the reporting of design flood information including the preparation of flood information

maps for the Lower Macdonald River catchment,

The information contained herein is suitable for the preparation of a subsequent Floodplain Risk

Management Study and Plan. A glossary of flood related terms is provided in Appendix A.


Webb, McKeown & Associates Pty Ltd22032:MacRiverFSFinal.wpd:18 August 2004 1

1. INTRODUCTION

1.1 Overview

Current flood planning levels used for the Macdonald River floodplain are based on a flood profile

prepared by Council staff in 1984. This profile was defined using a compilation of available flood

level information from past flood events and its relevance to corresponding design flood levels was

not known. In order to properly plan and manage both existing and future development within the

floodplain, there is a need to establish appropriate flood planning levels using a more rigorous, up

to date technical analysis.

In order to provide a solid technical foundation for flood planning levels within the valley, Webb,

McKeown & Associates were engaged by Hawkesbury City Council (HCC) to prepare this Flood

Study. The primary objectives of the study are:

• to define the flood behaviour for the lower reaches of the Macdonald River under existing

conditions,

• to establish numerical hydrologic and hydraulic models to determine flood flows, velocities

and levels for all design events,

• to formulate the models such that the effects on flood behaviour due to catchment

development and possible mitigation measures can be investigated in the future.

This report details the methodology used and the results of the design flood analysis. It includes:

• a summary of available data,

• reasons supporting the choice of hydrologic and hydraulic models,

• calibration and verification of these models,

• definition of design flood behaviour in accordance with the NSW Floodplain Management

Manual (2001).

All levels provided in this report are in metres (m) to Australian Height Datum (AHD) which is the

standard national survey reference plane approximating mean sea level.

1.2 Catchment Description

The Macdonald River is a tributary of the Hawkesbury River and drains a catchment area of

approximately 1845 km2 (Figure 1). The catchment consists of steeply vegetated slopes up to

elevations of around 800 m. The upper portions of the catchment consist predominantly of natural

bushland terrain. Downstream of the Womerah Creek confluence, the Macdonald River floodplain

is constrained by the steep relief of the surrounding hills and is typically between 300-500 m in

width.

The majority of development within the catchment consists of scattered free standing dwellings

located on rural acreages. The density of development increases in the downstream reaches of

the valley. The highest concentration of residential development is located approximately 1-2km



upstream of the Hawkesbury River junction, along the eastern side of the Macdonald River

floodplain.

1.3 General Morphology and Flood History

Flooding within the valley is primarily a consequence of surface runoff generated in the upper

reaches and from local catchments. The lower reaches of the Macdonald River can also be

affected by backwater effects from the Hawkesbury River during periods of coincident flooding.

Due to the long history of settlement within the Lower Macdonald valley, there is also an established

history of flooding with significant events known to have occurred in 1978, 1964, 1949 and as far

back as 1889. In particular, several successive major floods occurred on the Macdonald River

between 1949 and 1955. The most recent notable flood event on record occurred in August 1990.

The nature and form of the Macdonald River within the immediate study area is known to have

undergone significant changes over the last 150 years. An initial geomorphological analysis of the

Macdonald River floodplain is presented in Reference 1 (for completeness, this reference has been

reproduced in Appendix B). From a combination of available survey information and anecdotal

evidence provided by a range of local land owners, Reference 1 identifies several key changes in

the morphology of the river including:

• Significant changes to the in-channel geometry resulting from the deposition of sand along

a significant length of the river extending from upstream of St Albans (near Marlo Creek)

down to Wrights Creek. Reference 1 presents evidence indicating that the magnitude of

bed aggradation in some areas is as much as three (3) metres.

• Major changes in the shape and form of the overbank/floodplain areas immediately

adjacent to the main river channel. Reference 1 concludes that significant bank erosion

occurred during the major floods which followed the June 1949 event. It is suggested that

the sediment eroded from the immediate banks has contributed in large part to the level

of bed aggradation observed in the lower reaches of the Macdonald River.

• The formation of permanent lagoons in the lower reaches. Several of the low-lying smaller

tributaries were formed into permanent lagoons as a consequence of the bed aggradation

of the main river channel that resulted from the floods of the early 1950's.

Definitive information quantifying the overall changes in the longitudinal profile of the channel bed

over time is not available. However, in response to the aggradation of the channel bed, the

available information indicates that the width of the main river channel has been substantially

widened (as expected). For example, in the reach extending from 2km upstream of the Mogo

Creek junction down through to St Albans, anecdotal evidence suggests that the typical channel

width has increased up to five-fold following the 1949 flood event. The subsequent floods that

occurred between 1952 and 1955 were noted to result in significant bank erosion forming the broad

benched-type of overbank geometry that typifies the present floodplain within the immediate study

area. In the absence of more detailed information, the precise behaviour of the river in the future

is uncertain. For example, the gradual movement of the tidal limit upstream and the deepening of

the channel in the lower reaches of Wrights Creek (noted in Reference 1) provide some evidence



of bed recovery. However, Reference 1 also notes that the presence of indurated bed conditions

within a cut-off meander of the Macdonald River (located approximately 2kms upstream of Wrights

Creek confluence) is likely to limit the rate of bed recovery for these lower reaches.

Regardless of the precise behaviour of the river in the future, it is clear that the river and floodplain

can be considered to be morphologically active. From a flooding perspective, the aggraded bed

is likely to result in an increase in the occurrence of overbank flooding, although the magnitude of

the corresponding impacts on flood levels experienced during more extreme events will be relatively

lower (as flooding during the larger events occurs across the overall floodplain).

Importantly, for the present study, the presence of underlying changes in river morphology also

makes the precise interpretation of historical flood behaviour difficult to achieve. Within the context

of the present investigation, the level of morphological activity adds an element of uncertainty into

the design flood behaviour ultimately obtained. From a planning perspective, the potential for

ongoing-channel widening and/or significant bank erosion should be also be taken into account (in

addition to flooding considerations) when siting developments within the floodplain. These types

of analyses are further complicated by the sparseness of available historical information.



2. DATA

2.1 Previous Studies

To date, there have been no formal flood studies which have assessed the design flood behaviour

of the lower Macdonald River floodplain in specific detail. There are several published studies of

the hydrology and hydraulics of the Hawkesbury River which incorporate information concerning

the Macdonald River catchment. However, these studies were primarily focussed on Hawkesbury

River flood behaviour with the Macdonald River catchment considered in a broad context only.

Several studies which have provided some basis for the present detailed investigation include:

• Warragamba Dam Auxiliary Spillway EIS Flood Study (1996 - Reference 2)

Presented as a series of reports, this reference documents the development and use of hydrologic

and hydraulic models for the Hawkesbury-Nepean River system which were undertaken as part of

an EIS for the Warragamba Dam Auxiliary Spillway. The reports provide a detailed analysis of

historical rainfall and flood records across the broader Hawkesbury-Nepean catchment and include

information concerning the hydrologic modelling of the Macdonald River catchment.

• Lower Hawkesbury River Flood Study (1997 - Reference 3)

This study was part of a series of studies undertaken in the formulation of a floodplain management

plan for the Hawkesbury-Nepean valley. The study examines the flooding characteristics of the

Lower Hawkesbury River from Sackville to the ocean. A flood frequency analysis was undertaken

for the streamflow gauge at St Albans and design discharge estimates were derived as part of this

analysis. No specific information on the flood hydraulics for the lower Macdonald floodplain is

presented in the report.

2.2 Topographic and Hydrographic Information

1:100000 scale and 1:25000 scale topographic maps were used to provide an overview of the

broader topographic features of the catchment. The 1:100000 map series of the area was also

used to delineate the sub-areas for the hydrologic modelling (discussed later in Section 4).

Prior to commencement of the current study, the available cross-section information was limited

to a hydrographic survey below the tidal limit of the lower Macdonald River. This survey was

undertaken in the early 1980's by the then NSW Department of Public Works (PWD). This data

has been used in subsequent hydraulic modelling investigations for the Hawkesbury River

(References 2 and 3).



As part of the present study, additional surveys were commissioned to:

• extend the hydrographic survey upstream of the tidal limit, and

• provide overbank detail to correspond with the channel sections obtained from the

hydrosurvey.

The locations of the new cross-sections were determined based on a field inspection conducted by

Webb McKeown in conjunction with Council staff. Consideration was also given to the locations

of the existing hydrosurvey. The additional survey information was obtained by Council using

GPS-based techniques. The new survey information is estimated to have an order of accuracy of

±0.05 m in general although there may be localised errors of up to ±0.25 m in some locations.

The locations of all available survey information used in the study are shown in Figure 2.

2.3 Rainfall Data

There are a number of daily-read rainfall gauges and pluviometers located within or in close

proximity to the Macdonald River catchment. The quality of data describing recorded actual rainfall

patterns has improved following the installation of several pluviometers within the catchment by

Sydney Water in June 1990. Prior to this, the description of the rainfall temporal patterns for

historical events relied on records collected outside of the catchment. An exception to this was a

pluviometer at Eraring which was operated for an unknown period by the then Electricity

Commission of NSW from around 1977. These records were sought during the initial phases of

the present Study. Unfortunately, as a result of the restructuring within the power utility sector, the

data records for this station could not be sourced. Details of the available rainfall stations in the

immediate vicinity of the catchment are provided in Table 1 and the corresponding locations are

shown in Figure 3.

Table 1: Available Rainfall Stations

Number Name Source Coverage Type061296 Howes Valley (Owensdale) BoM 1970 - Present Daily061119 Wisemans Ferry (Old Post Office) BoM 1903 - Present Daily061284 Lambton BoM 1870 - 1920 Daily061030 Howes Valley (Kindarun) BoM 1914 - 1975 Daily061217 St Albans BoM 1963 - Present Daily061211 St Albans (Mogo Creek) BoM 1963 - Present Daily067044 Lower Portland BoM 1963 - 1992 Daily061209 Putty Post Office (Putty Composite) BoM 1977 - Present Daily, Pluvio.061217 Colo Heights Composite BoM 1962 - Present Daily, Pluvio.061336 Putty (The Gibba) BoM 1975 - Present Daily, Pluvio.061351 Peats Ridge (Waratah Rd) BoM 1981 - Present Daily, Pluvio.561103 Howes Valley (Noisy Point) AWT 1990 - Present Pluviograph561102 Putty Forest (3 Ways) AWT 1990 - Present Pluviograph561107 Mt Calore AWT 1990 - Present Pluviograph561106 Bala AWT 1990 - Present Pluviograph561108 Womerah AWT 1990 - Present Pluviograph561101 Mangrove Mtn (Dubbo Gully) AWT 1990 - Present Pluviograph



2.4 Streamflow Gauging Stations

Streamflow gauging stations on the Macdonald River are located at St Albans and Howes Valley

(Table 2). Both stations were originally established by the NSW Department of Water Resources

but are now operated and maintained by Department of Infrastructure, Planning and Natural

Resources (DIPNR). Continuous water level recordings commenced in 1972 at St Albans and in

1976 at Howes Valley. At both sites the control is based on a sandy bed and no high flow gauging

has been undertaken. Hence, a degree of caution is needed when interpreting the observed flow

records, particularly for smaller events. For the St Albans gauge, the data record is intermittent with

significant portions of missing data.

Table 2: Available Streamflow Gauging Stations

Number Name Catchment

Area (km2)

Years of Record Maximum Gauging

(m above Gauge Zero)

212010 St Albans 1680 1954 - Present 2.99 m on 05/03/1976*

212021 Howes Valley 299 1972 - Present 2.88 m on 20/03/1978

* Estimate of Gauge Zero at St Albans is 2.86 mAHD (HCC Council Survey, 2003).

2.5 Historical Flood Levels

A number of flood level records exist for different sites throughout the Lower Macdonald River

floodplain. For the present study, historical information was obtained from a number of sources

including Council records and existing hydrologic and technical reports related to the area.

In addition, local residents were canvassed during the initial stages of the present study for

information relating to past floods. Where possible, this information was used to provide flood

height estimates, the levels of which were surveyed during the compilation of overbank

cross-section data. A summary of available information is presented in Table 3.



Table 3: Recorded Flood Levels

Event Location Chainage from

Hawkesbury River (m)

Level

(mAHD)

Source(see footnote)

Council Point

Reference No.

1896 Wrights Ck

Junction

13890 9.3 Council Profile

1984

-

1949 29440 15.83 Council

Survey 2003

108

1949 28110 14.99 Council

Survey 2003

503

1949 27140 14.2 Council

Survey 2003

526

1949 ~200m U/S of

St Albans

22185 15.1 Council

Survey 2004

1000

1949 St Albans 22185 14.3 Council

Survey 2003

549

1949 St Albans 22185 14.65 Council Profile

1984

-

1949 Wrights Ck

Junction


1984

-

1949 Wrights Ck

Junction

13890 10.6 Council

Survey 2003

441

Mar 1978 29440 14.64 Council

Survey 2003

105

Mar 1978 27140 13.2 Council

Survey 2003

525

Mar 1978 16570 10.6 Council

Survey 2003

151

Mar 1978 St Albans 22185 11.25 Council Profile

1984

-

Mar 1978 Wrights Ck

Junction


1984

-

Mar 1978 1910 4.9 Council Profile

1984

-

Aug 1990 St Albans 22185 8.75 Sydney

Catchment

Auth.

-

NOTE: ‘Council Profile 1984' refers to a Flood Profile plan established by Council in 1984.

A photographic summary of the locations of the observed flood heights obtained by Council for this

study is provided in Appendix C. It is recommended that Council pursue the collection of this type

of flood-related information following future flood events.

A detailed discussion concerning the available historical flood information is provided in Section 5.2.



CATCHMENT INFORMATIONsub-areasland-use

percentage Imperviousstorage basin data

observed runoff volumes or rates

RAINFALL DATAhistorical or design storm events

rainfall depths (Isohyets)temporal patterns (intensity v

time)

MODEL BOUNDARY CONDITIONSdownstream ocean/tide levelsupstream inflow hydrographsdirect rainfall - lateral inflows

CALIBRATION/VERIFICATIONComputational Modelling Software

HYDROLOGIC ANALYSIS

QUANTIFY CATCHMENT RUNOFFestimated flow hydrographs

HYDRAULIC CHARACTERISTICS

topographic databridge/culvert details

overflow weir structuresdefine flow paths

stream roughness values

OBSERVED FLOOD BEHAVIOURpeak heights

stage or flow hydrographsrelative timing of events

velocity estimatesgeneral observations

COMPUTER MODEL PARAMETERSstorage-routing coefficient

rainfall losses

CALIBRATION/VERIFICATIONComputational Modelling

Software

QUANTIFY FLOOD BEHAVIOURflood levels

flowsvelocities

HYDRAULIC ANALYSIS

REVIEW

3. APPROACH ADOPTED

Initially, a hydrologic model (WBNM) was established for the entire catchment and used to convert

rainfall data into streamflow for input to a hydraulic model of the lower Macdonald floodplain. To

ensure confidence in the results produced, both the hydrologic and hydraulic models require

calibration and verification against observed historical events. The hydrologic model was calibrated

to the available streamflow data for the St Albans gauge. The hydraulic model was then calibrated

to the available streamflow and peak flood level data where possible. Using the calibrated models,

the design flood behaviour was then quantified for a range of design storm events up to and

including an extreme event approximating the PMF. A representation of the Flood Study process

is shown in Diagram 1.

Diagram 1: Flood Study Process



4. HYDROLOGIC MODEL

4.1 Hydrologic Model Description

Hydrologic models suitable for design flood estimation are described in AR&R87 (Reference 4).

In current Australian engineering practice, examples of the more commonly used runoff routing

models are RORB, RAFTS and the Watershed Bounded Network Model (WBNM). These models

allow the rainfall depth to vary both spatially and temporally over the catchment and readily lend

themselves to calibration against recorded data. Details of these models are discussed in

Reference 4.

The MacDonald River catchment has been previously modelled using RORB (Reference 2). The

existing RORB model was established to provide design discharges for a much larger study which

assessed runoff behaviour for the overall Hawkesbury-Nepean catchment. The Macdonald River

catchment was only a small sub-catchment and consequently was only defined using a limited

number of sub-areas. Both RORB and WBNM offer similar features. However, WBNM is easier

to use and requires less data. It also has the advantage over RORB of using different approaches

to modelling overland runoff and streamflow. For these reasons and in order to provide a greater

level of detail, a WBNM model was established for the present study.

4.2 Model Configuration

The WBNM model simulates a catchment and its tributaries as a series of sub-catchment areas

based on watershed boundaries linked together to replicate rainfall/runoff process through the

natural stream network. The adopted sub-catchment division is shown on Figure 4. The model input

data includes definition of physical characteristics such as:

• surface area,

• proportion developed (imperviousness),

• stream shortening.

The model established for this study comprised a total of 35 sub-areas and included all tributaries

upstream of the Macdonald River confluence with the Hawkesbury River. The layout of the

sub-areas was defined to provide a reasonable level of spatial detail within the catchment and to

provide flow hydrographs at specific locations. For example, the model was structured to provide

primary inflows at the upstream limits of the hydraulic model as wells as hydrographs corresponding

to streamflow gauging sites to assist with model calibration and verification. Catchment areas for

each sub-area were determined from the 1:100000 series topographic maps. As a check, the total

catchment area draining to St Albans in the WBNM model was found to be within 3% of the

catchment area quoted for the gauging station at St Albans. The original WBNM areas were then

slightly adjusted (as a whole) to match the catchment area reported for the St Albans gauge. Given

the scale of the hydrologic modelling and the limited nature of development within the overall

catchment, no impervious areas were defined in the WBNM model.



4.3 Calibration and Verification

4.3.1 Key Model Parameters

In calibrating the WBNM model, several parameters can be varied to achieve a fit to observed data:

• Non-Linearity Exponent of the Storage Routing Equation

This is an internal variable which modifies the storage routing functions in the model. For

the present study, it was set at the recommended value (0.77).

• Rainfall Losses

Two parameters, initial loss (IL) and continuing loss (CL), modify the amount of rainfall

excess to be routed through the model storages.

• Lag Parameter

The Lag Parameter affects the timing of the catchment response to the runoff process and

is subject to catchment size, shape and slope.

The WBNM model was calibrated by adjusting these parameters in order to match the recorded

streamflow hydrographs available for a given event(s). The performance of the calibrated model

is then verified by comparison with an independent historical flood event(s).

4.3.2 Historical Events

The value of a particular flood for calibration of the hydrologic model largely depends on the

following:

• quantity and quality of daily rainfall data,

• quantity and quality of pluviograph data and the proximity of the gauges to the catchment,

• magnitude of the flood event.

Taking these factors into account, the calibration of the WBNM model was principally based on the

March 1978 flood event, this being the largest flood event having sufficient rainfall and streamflow

data suitable for calibration. Verification was provided by the August 1990 flood, whilst the smaller

floods in August 1986 and April 1988 were used as additional confirmation of model performance.

For each historical event, rainfall depths and temporal patterns were assigned based on the

available rainfall totals, isohyetal maps and pluviograph records (refer Figures 5 to 8).

An assessment of the likely baseflow component for each of the estimated hydrographs at

St Albans was made for all of the above historical events using the techniques outlined in

Section 8.3 of AR&R87 (Reference 4). For the March 1978, significant gaps in the data record

during the recession limb prevented a reasonable estimation of baseflow component. However,

analysis of the remaining three events showed that the baseflow portion of the overall hydrograph

volume was small and unlikely to affect the flood behaviour of the catchment in the context of the

present study. In view of this, no separation of baseflow was made from the historical flow

hydrographs used to calibrate the WBNM model at St Albans.



The adopted model parameters are shown in Table 4. A comparison of the results produced by

the WBNM model with the observed streamflow data for each historical event is provided in Table 5

and in Figures 9 to 12.

The outcomes of the model calibration and verification are discussed further in Section 4.4.

Table 4: WBNM Model Calibration: Adopted Model Parameters

Storm Non-linearity

Exponent of

Storage

IL

(mm)

CL

(mm/h)

Lag

Parameter

Mar 1978 0.77 70 3.0 1.90

Aug 1990 0.77 37 1.0 1.90

Aug 1986 0.77 85 6.5 1.90

Apr 1988 0.77 50 1.0 1.90

Table 5: Historical Storms: WBNM Model Performance

Storm Observed

Peak

Discharge

(m3/s)

Modelled

Peak

Discharge

(m3/s)

Relative

Difference

(%)

Observed

Volume

(m3 x 106)

Modelled

Volume

(m3 x 106)

Relative

Difference

(%)

Mar 1978 880 920 5% 129 133 3%

Aug 1990 500 510 2% 97 79 -19%

Aug 1986 100 120 20% 17 15 -12%

Apr 1988 130 130 0% 20 16 -20%

4.4 Discussion

The results of the WBNM calibration for the March 1978 event (refer Table 5 and Figure 9) indicate

that the WBNM model matches both the peak discharge and the runoff volume reasonably well.

However in comparison to the modelled hydrograph at St Albans, the shape of the rising limb of the

observed hydrograph shows a greater degree of variation, having a distinct ‘kink’ between 55 and

60 hours following the start of the rainfall event (Figure 9). The inability of the predicted hydrograph

to reproduce this behaviour is attributed to uncertainties in the rainfall temporal patterns adopted

for this event. As noted previously (Section 2.3), there were no pluviograph records within the

Macdonald River catchment available for the March 1978 event. Given these limitations the WBNM

model calibration is considered satisfactory.

In view of the available rainfall and streamflow data, the more recent August 1990 event was

considered the most appropriate to verify the performance of the calibrated WBNM model. Unlike

the March 1978 event, there were several pluviographs operating within the study catchment during

the August 1990 event. The results obtained (refer Figure 10 and Table 5) indicate that the model



reproduced the peak discharge and the general shape of the observed hydrograph at St Albans

well. This is attributed to the availability of recorded pluviograph data at several locations within the

catchment. However, it is noted that the model under-predicts the observed runoff volume by up

to 20%. Although a range of continuing loss rates were tested to improve the model results, a

continuing rainfall loss of 1.0 mm/hour was ultimately adopted. Given the nature of the catchment,

it was considered that the use of a continuing loss rate less than 1.0 mm/hour would be unrealistic.

Any errors in the model results were therefore attributed to uncertainties in the rainfall totals

assigned to the various sub-areas for this event. In the absence of additional data which might

better describe the spatial variation of rainfall across the catchment in more detail, the verification

of the WBNM for the August 1990 event was considered reasonable.

Although they are significantly smaller than either the March 1978 or August 1990 events, the April

1988 and August 1986 flood events were also simulated in WBNM to provide some confirmation

(re-assurance) of the overall model performance for both large and small events.

Figure 11 shows the results for the April 1988 event. Although the WBNM model matches the peak

discharge well, the timing of the simulated hydrograph is distinctly different. However, it should be

noted that again there were no pluviograph records available within the catchment. Hence, it is

therefore likely that there may be errors in the assigned temporal pattern for this event. Translation

of the modelled hydrograph indicated that main source of discrepancy in runoff volume is

associated with the recession portion of the hydrograph.

In order to provide a reasonable fit for the August 1986 event, the adoption of a significant

continuing loss (6.5 mm/hr) was required. This would seem to reflect clear deficiencies in the

definition of the historical rainfall pattern for this event (Figure 12). The double peak of the

observed hydrograph further highlights these deficiencies. As per the April 1988 event, there was

limited temporal information available for this event.

Overall, it is considered that the calibration and verification results indicate that the model is

simulating the rainfall/ runoff process reasonably well. The timing and overall fit of the larger flood

events, used for calibration and verification, are considered to be good. While the model nominally

appears to underestimate the runoff volume of observed events, it is still considered to be suitable

for estimating flows for design storms. Design storms have a single temporal pattern and relatively

uniform spatial pattern and are therefore not as susceptible to the variable nature (peaky) of flows

generated from observed storm events.



5. HYDRAULIC MODEL

5.1 General Approach and Model Establishment

Given the objectives of the study, the nature of the flowpaths and watercourses within the Lower

Macdonald valley and the available data, a one-dimensional (1D) flow representation provides the

most efficient and effective representation of flood behaviour. This is particularly so as the

floodplain is bounded by steep terrain and is therefore relatively confined throughout the study

reach.

A 1D hydraulic model was established using the MIKE11 software package (Reference 5). The

MIKE11 model is widely used in flood engineering both within Australia and internationally. It is a

proven tool for the dynamic modelling of branched networks with complex cross-sections and

hydraulic control structures.

The MIKE11 model layout of the Macdonald River extends from just upstream of the Womerah

Creek junction down to the confluence with the Hawkesbury River at Wisemans Ferry (Figure 13).

The lower reach of Wrights Creek was also included as part of the model. The model

cross-sections were derived from the GPS survey data (discussed previously in Section 2.2).

Where possible, the in-channel definition of each section was supplemented by the available

hydrosurvey data of the Macdonald River (surveyed in 1984 by the then NSW Public Works

Department).

The locations of the river crossings in the immediate study area were identified from available

mapping information and verified during an initial site inspection. The details of several smaller

low-lying crossings were obtained as part of the ground survey component of the study. For the

bridge crossing of the Macdonald River at St Albans, detailed plans were obtained from the Roads

and Traffic Authority (RTA). Detailed modelling of the St Albans bridge indicated that only minor

headlosses less than 5cm (0.05m) would occur at this location due to the support piers.

5.2 Hydraulic Model Calibration and Verification

The hydraulic efficiency of the river is represented (in part) in the MIKE11 model by the stream

roughness or friction factor formulated as Manning’s ‘n’. This factor describes the net influence of:

• channel roughness

• channel sinuosity

• vegetation and other debris within the channel/overbank.

• bed forms and shape.

Consistent with the quality and reliability of historical flood data, the March 1978 event was used

for the calibration of the MIKE11 model. The Manning’s ‘n’ values used in the model were adjusted

within reasonable vicinity to best reproduce the observed flood behaviour for this event. A limited



form of model verification was then provided through a comparison of the model results with the

recorded stage hydrograph at St Albans for the August 1990 event.

For each event, the boundary conditions for the MIKE11 model consist of a series of time-varying

inflow hydrographs obtained from the calibrated WBNM model and observed stage hydrographs

for the downstream model boundary at Wisemans Ferry (Reference 3).

5.2.1 March 1978 Event

Following a series of trial runs, it was found that the following set of Manning’s ‘n’ values best

reproduced the observed flood behaviour for the March 1978 event:

• n=0.037: defined for the Macdonald River reach between Womerah Creek to approximately

4.5km downstream of St Albans

• n=0.041: defined for the remaining lower reaches of the Macdonald River including Wrights

Creek.

The two values are reasonably similar in magnitude and were applied uniformly across the model

cross-sections. Based upon site inspections, comparison with published values and values used

in past studies of similar catchments, the values above are considered to be representative of the

surface roughness expected across the entire floodplain. The model results in terms of peak flood

height profiles and time varying hydrographs at St Albans for the March 1978 event are presented

in Figures 14 to 16.

A comparison of modelled and predicted heights along the Macdonald River branch is presented

in Figure 14. The results generally indicate a good agreement between modelled and observed

flood heights. Localised exceptions are noted to occur at several locations:

• For those locations upstream of St Albans, it was found that the hydraulic model

underestimated the observed levels, producing a flatter flood gradient for the March 1978 event.

A detailed review of the historical flood information suggests that the observed levels are fairly

reliable. However, it was found that physically unrealistic roughness factors were needed to be

specified in the hydraulic model to reproduce the flood levels in these locations. The application

of these types of bed roughness values resulted in the water levels at St Albans being

significantly over-estimated. Reasons for the discrepancies in the uppermost reaches could

include event-based morphological changes, localised topographic features present during the

1978 event and limitations in the representation of the river system due to the available cross-

section data. These factors have the potential to introduce a notable degree of uncertainty to

the analysis. Hence, given the reliability of the record at St Albans, the adjustment of the bed

roughness for the upper most reaches to match the observed levels was not undertaken and

the model calibration shown was adopted for design flood modelling. The implications of the

model estimates in this reach are discussed further in the context of design flood level

estimates in Section 7.3.



• There is a single flood observation of around 10.6 mAHD for the 1978 event located

approximately 1km upstream of the Wrights Creek junction (Figure 14). In comparison, the

MIKE11 model estimates a corresponding flood peak of 8.1 mAHD. Given the match between

the model and observed levels at Wrights Creek and further downstream, the simulated peak

profile through this reach is considered reasonable. Further, a review of surveyed sections and

overall floodplain topography does not overtly indicate the presence of underlying morphological

factors that may have contributed to the higher observed level. For these reasons, the adopted

model calibration in this area was considered sufficient.

From the time-series comparisons presented in Figures 15 and 16, it is evident that the MIKE11

model reproduces both the peak and the timing of the observed flood behaviour reasonably well

at St Albans. Apart from some attenuation (due to an improved representation of channel routing),

the simulated discharge hydrograph directly reflects the corresponding hydrograph estimated by

the WBNM model (as expected). The discrepancies between the MIKE11 and observed

hydrographs can therefore be attributed in large part to the shortcomings in the ability of the WBNM

model to more accurately represent the observed flow behaviour for this event. The discrepancies

preceding the main storm burst reflect the start of the rainfall burst used in the WBNM model and

are not representative of the performance of the MIKE11 model.

Based on the results discussed above, the MIKE11 model is considered to be reasonably well

calibrated within the limitations of the available data and potential uncertainties.

5.2.2 August 1990 Event

As a limited form of model verification, the MIKE11 results were compared to the recorded water

levels and estimated discharges at St Albans (Figures 17 and 19). As per the March 1978 event,

discrepancies between the observed and simulated hydrograph shapes are a consequence of the

hydrological modelling. The MIKE11 model matches the peak flood level reasonably well. The

good agreement shown for the August 1990 event indicates that the calibrated set of models are

performing reliably and are suitable for the estimation of design flood behaviour.



6. DESIGN FLOWS

6.1 Overview

There are two basic approaches to determining design flood discharges:

• flood frequency analysis - based upon a statistical analysis of the flood record, and

• rainfall/runoff routing - design rainfalls are processed by a suite of computer models to produce

estimates of design flood behaviour.

The approach adopted for this study reflects current engineering practice and has been based on

the quality and quantity of available data. The flood frequency approach requires a reasonably

complete homogeneous record of flows over a number of decades to give satisfactory results.

There are some 30 years of streamflow estimates available for the St Albans gauging station

(Station 212010). Although the length of record is relatively short (<50 years), a flood frequency

analysis was undertaken to provide design discharge estimates to compare against the

corresponding estimates derived from rainfall/runoff routing.

6.2 Hydrologic Modelling

The calibrated WBNM model was used to derive design flows for input to the MIKE11 hydraulic

model. Flow hydrographs were obtained for the 500 Year, 200 Year, 100 Year, 50 Year, 20 Year,

10 Year, 5 Year ARI flood events and an Extreme event.

For each event (up to and including the 500 year ARI event), spatial and temporal design rainfall

patterns were obtained from AR&R for durations ranging from 12 hours to 72 hours. The spatial

pattern was based on that derived for the 36 hour duration 100 year ARI event for the Macdonald

catchment (Reference 2). In all cases, an areal reduction factor of 0.92 was adopted (following

extrapolation from information provided in AR&R). An initial loss of 70 mm/hr was adopted for all

design events. This value was consistent with previous studies (e.g References 2 and 3) and

reflect recommended values provided in AR&R 1987 (Reference 4) and more recent information

detailed in Walsh et.al. (Reference 6). A continuing loss of 2.5mm per hour was used for all design

events up to and including the 500 Year ARI storm. For the extreme event, a continuing loss of

1mm per hour was adopted.

Using the WBNM model, design discharge hydrographs were obtained for storm durations ranging

from 12 hours up to 72 hours. For the lower reaches of the catchment (i.e. downstream of

St Albans), the results showed that the critical duration was consistently between 36 hours to

48 hours, regardless of the magnitude of the design event (Table 6). Given that the 48 hour storm

duration produced slightly larger peaks, the 48 hour duration was adopted as the design storm

duration for the hydraulic modelling.



Table 6: Modelled Peak Flows (m3/s) at St Albans

Storm Duration (hours)

Frequency (ARI) 12 24 36 48 72

5 Year 225 380 630 720 500

10 Year 410 690 1040 1145 700

20 Year 710 1160 1650 1715 1065

50 Year 1190 1860 2440 2470 1710

100 Year 1600 2450 3140 3200 2260

200 Year 2040 3085 3890 3995 2830

500 Year 2685 3995 4960 5120 3640

Note: Model results obtained using an initial loss of 70 mm, an Areal Reduction Factor of 0.92 and a

Continuing Loss Rate of 2.5 mm/hr.

To assess the impact of key parameters on the modelled 100 Year ARI event, a range of sensitivity

analyses were undertaken. Specifically, these analyses examined the impacts of varying the initial

loss and areal reduction factor for both 36 hour and 48 hour duration storm events. The findings

are summarised in Tables 6 and 7.

Table 7: Sensitivity of Initial Loss Values - 100 Year ARI Peak Flow Estimates

40mm IL

Rel. Diff.(40mm IL

vs. 70mm IL)

70mm IL(adopted)

Rel. Diff.(100mm IL

vs. 70mm IL)

100mm IL

36 Hour Storm Qpeak:3660m3/s 17% Qpeak: 3140m3/s 15% Qpeak: 2490m3/s

48 Hour Storm Qpeak: 3675m3/s 15% Qpeak: 3200m3/s 18% Qpeak: 2640m3/s

Table 8: Sensitivity of Areal Reduction Factors - 100 Year ARI Peak Flow Estimates

ARF=0.76

Rel. Diff.

(0.76 vs.

0.92)

ARF=0.85

Rel. Diff.

(0.85 vs.

0.92)

ARF=0.92

(adopted)



Table 7 shows that the impact of different loss values upon the simulated peak discharge was

relatively minor. Compared to the adopted value of 70 mm, variations in the initial loss resulted in

changes to the predicted peak discharges of not more than 15%. This outcome is to be expected

given the relatively long critical duration for the catchment.

Not surprisingly, there is a notable impact on predicted peak discharges and overall hydrograph

volume due to variations in the Areal Reduction Factor (ARF). Given the objectives of this study,

the size of the catchment and the duration of the storm events, the adopted value of 0.92 was

considered appropriate. In comparison to lower values, the adopted value provides a conservative



estimate that is consistent with current AR&R recommendations regarding ARF values. More

detailed depth-area-duration analyses were considered to be outside the scope of the present

study.

6.3 Flood Frequency Analysis

Using the available data for the gauging station at St Albans (Station 212010), an annual flood

series was determined (Table 9). Data was sourced from both database records (Pinnenna V6),

the Sydney Catchment Authority and from original gauge cards supplied by DIPNR.

Table 9: Annual Flood Series: Macdonald River at St Albans (Station 212010)

Year Peak Discharge (m3/s) Year Peak Discharge (m3/s)

1955 600 1973 190

1956 No Record 1974 440

1957 No Record 1975 150

1958 240 1976 270

1959 90 1977 660

1960 40 1978 890

1961 60 1979 70

1962 300 1980 5

1963 600 1981 300

1964 740 1982 120

1965 30 1983 30

1966 20 1984 210

1967 350 1985 150

1968 90 1986 100

1969 120 1987 50

1970 20 1988 390

1971 190 1989 510

1972 40 1990 540

In accordance with AR&R 1987 (Reference 4), the annual series was used to derive a Log Pearson

Type III distribution for flood frequency estimates. The resulting fit is plotted together with the

original data and 90-th percentile confidence limits in Figure 20. The estimated design discharges

are presented in Table 10. For comparison, the corresponding design discharge estimates

obtained from the rainfall-runoff modelling (Section 6.2) are also included in Table 10.



Table 10: Flood Frequency Analyses: Macdonald River at St Albans (Station 212010)

Frequency

(AEP)

Original Annual Series

Discharge (m3/s)

Revised Annual Series (incl.

1949 event) Discharge (m3/s)

WBNM Modelling

Discharge (m3/s)*

20% 430 485 665

10% 620 860 1108

5% 800 1365 1690

2% 1005 2275 2470

1% 1140 3175 3200

0.5% 1260 4290 3990

0.2% 1390 6150 5120

* Note: Discharges for 48 hour duration storm, estimates adjusted to account for annual series comparison.

Prior to the commencement of streamflow gauging at St Albans, there is evidence of several

significant floods occurring on the Macdonald River including events in 1889, 1913 and between

1949 through to 1955. Of these events, a number of flood level records exist for different locations

for the 1949 event, whilst there is only a single reported level for the 1896 event (refer to Table 3).

In order to extend the period across which the flood frequency analysis was undertaken, the peak

flood levels for the 1949 event at St Albans were included to derive an estimate of the

corresponding peak discharge.

For the 1949 event, a number of levels have been recorded in St Albans, including a level of

14.6 mAHD at St Albans bridge and 14.3 mAHD at the Settlers Arms Inn (Table 3). It should be

noted that the reliability of the flood level quoted for St Albans bridge is not known. Attempts to

obtain evidence of the original survey records proved unsuccessful. The results from the MIKE11

model were used to extend the stage-discharge relationship at St Albans to incorporate both these

levels, the corresponding discharges were estimated to range from 2950 m3/s up to 3180 m3/s.

These flows have been estimated assuming that there are no significant tailwater impacts due to

concurrent flooding on the Hawkesbury River. As a conservative estimate, the higher flow of

3180 m3/s was adopted for use in a revised flood frequency analysis that incorporated the 1949

event.

The revised analysis was undertaken using the Bayesian flood frequency inference techniques

provided by the FLIKE flood frequency software package (Reference 7). Using this approach, the

1949 event was incorporated into the analysis essentially as the largest flood to have occurred

between 1913 and 1949 (the 1913 event being the next earliest date of known significant flooding -

the relative size if the 1913 event compared to the 1949 event is not known). The outcome of the

revised flood frequency analysis incorporating the 1949 event is shown in Table 10 and Figure 20.



6.4 Adopted Design Flows

The comparison of discharges in Table 10 indicates that there is a significant degree of variation

in the design flow estimates obtained from the different methods. The results indicate that the fitted

frequency distribution is sensitive to the addition of the 1949 event. For example, the 100 year ARI

design estimate increased by 80% after the 1949 event was included as part of the annual series.

This degree of sensitivity is directly attributable to the relatively short length of record used in the

analysis. It is therefore suggested that the estimates obtained from the flood frequency analysis

of gauged records are only valid for AEP’s of 30% or greater (based on recommendations

presented in Section 12.6 of AR&R 1987 (Reference 4).

The estimate of the 1% AEP discharge, for the revised analysis, is however comparable to that

obtained from the WBNM model. For more extreme events, the revised frequency analysis

estimates are slightly higher (typically by between 8% and 20%) than the WBNM estimates. In

contrast, Table 10 shows that for more frequent events (such as the 20% or 5% AEP flood) the

design flow estimates obtained from the WBNM model were considerably higher than those

obtained via flood frequency analyses. This trend may be attributable to the fact that the WBNM

estimates are derived from a partial series (Walsh, pers. Comm. 2004). The hydrologic modelling

undertaken using the WBNM model has adopted a constant initial loss value, regardless of the

frequency of the particular event. However, in other studies comparing design estimates from

hydrologic models with those obtained from partial-series based flood frequency analyses, it has

been shown that higher initial losses were needed in the hydrologic model to match the flood

frequency estimates for the more frequent events (Reference 6).

The discrepancy for more frequent events may also be a consequence of the information used to

derive the design rainfall information for AR&R 1987 (Reference 4). As part of the broader

Hawkesbury-Nepean study conducted for Sydney Water in the mid-1990's, the Bureau of

Meteorology were commissioned to undertake a study of information from twenty long term rainfall

gauges (Reference 2). The Bureau's analysis indicated that the rainfall depths recorded at

Wisemans Ferry were up to 20% lower in comparison to those recorded at surrounding rainfall

stations (including the rainfall gauge at Maroota). Advice from the Bureau suggested that this

rainfall shadowing effect at Wisemans Ferry was not incorporated into the information used to

derive the design rainfall data for AR&R. For the Macdonald catchment, this effect would act to

reduce the spatial rainfall gradient down through the catchment, thereby reducing the design rainfall

in the lower part of the catchment. This effect may account for the higher design estimates

produced by the WBNM model for smaller events.

In comparison to previous studies, the WBNM estimates shown in Table 10 are consistent with

design discharges derived from RORB modelling of the catchment undertaken for Sydney Water

(Reference 2). In contrast, the design flows adopted for Macdonald River for hydraulic modelling

of the Lower Hawkesbury (Reference 3) are considerably lower than those obtained for the present

study. For example, in the 100 Year ARI event, the Lower Hawkesbury Flood Study (Reference 3)

adopted a peak discharge of 1,600 m3/s which compares to 3940 m3/s obtained from WBNM

modelling. However, this was using a much lower ARF (0.76) than the present study. Using these



lower values in the WBNM model produces a corresponding discharge of around 2300 m3/s for the

48 hour duration event. Additionally, it should be noted that only 50% of the design rainfall was

available as rainfall excess. In view of this and in line with the objectives of this study, the decision

to adopt an ARF of 0.92 was considered more appropriate.

Given the relatively good agreement between the WBNM results and the revised flood frequency

analysis (incorporating the 1949 event), the design discharge hydrographs provided by the WBNM

model were used as inflow boundary conditions for the hydraulic modelling to define design flood

levels throughout the floodplain. Due to the large size of the catchment area, an estimation of a

PMF using standard BoM techniques could not be undertaken. As an approximation, the design

flow hydrographs for an “Extreme event” were estimated as being three times the corresponding

flows for the 100 Year ARI event.



7. DESIGN FLOOD (HYDRAULIC) MODELLING

7.1 Tailwater Conditions

In addition to runoff from the catchment, the lower reaches of the Macdonald River floodplain can

also be influenced by backwater effects resulting from concurrent flooding of the Hawkesbury River.

The Macdonald River catchment is much smaller in size, compared to the total area draining to the

Hawkesbury River at Wisemans Ferry. Hence, for a given flood event, it is more likely that the flood

levels in the upper part of the floodplain would peak prior to the corresponding flood peak occurs

in the Hawkesbury River. Consideration must therefore be given to accounting for the joint

probability of coincident flooding from both catchment runoff and backwater effects from the

Hawkesbury River.

A full joint probability analysis is beyond the scope of the present study. Traditionally, it is common

practice to estimate design flood levels in these situations using a ‘peak envelope’ approach that

adopts the highest of the predicted levels from the two mechanisms. This is the approach that has

been adopted for this study. For events up to and including the 20 Year ARI event, a constant level

of 1.5 mAHD was used at the downstream boundary of the MIKE11 model to derive the design

flood levels for the upper reaches of the Macdonald River Floodplain. This tailwater level

corresponds (nominally) to the 100 year design ocean level at Broken Bay. Similarly, a peak

tailwater level of 4.4 mAHD (corresponding to the 20 Year ARI design flood level at Wisemans

Ferry) has been adopted for the 100 Year, 200 Year and 500 Year ARI events. For each of these

runs, the peak flood level for the lower reaches has been defined as the peak level estimate from

the MIKE11 model or the corresponding design level at Wisemans Ferry (Table 11), whichever is

the higher.

Table 11: Design Flood Levels at Wisemans Ferry

Event Level (mAHD)

at Wisemans FerryExtreme 16.3

500 Year ARI 9.5 *

200 Year ARI 8.0 *

100 Year ARI 6.7

50 Year ARI 5.6

20 Year ARI 4.4

10 Year ARI 3.9 *

5 Year ARI 3.2

Notes: * Interpolated for the purposes of this study.Source: Reference 3



7.2 Design Flood Results

7.2.1 Flood Levels, Extents and Flow Distribution

Peak height profiles for the Extreme event and all other modelled design flood events are shown

on Figure 21. A summary of design flood levels at model cross-sections is presented in Table 12.

A detailed listing of the design flood results (peak flood levels, flows and velocities) at locations

throughout the model reaches is provided in Appendix D.

A GIS-based representation of the design flood levels at each of the model cross-sections is shown

on Figures 22 to 29 for each event. The extent of inundation is also included for the 100 Year ARI,

20 Year ARI and Extreme flood events on Figures 24, 26 and 29 respectively. It should be noted

that these extents are indicative only and have been determined based upon the processed survey

data used to define the model cross-sections. It is recommended that the actual extent for any

given location be confirmed with detailed local survey. The corresponding electronic GIS datafiles

used to produce these figures have been provided for use in Council’s GIS database. These files

have been generated for each event and indicate details of the peak discharge, peak flood level

and peak velocity at each model cross-section. It is imperative that this GIS-based information be

interpreted in the context of the information presented in this report. Importantly, the GIS

information should be interpreted from a broad perspective that takes into account the overall

floodplain as opposed to an interpretation that considers the results in isolation or on a localised

basis only. The metadata for the GIS information includes a reference to this report to assist

Council in this regard.

Given that detailed cross-section information was available at a limited number of locations and in

accordance with the 1D modelling approach adopted, an estimate of the flow distribution across

the floodplain was made on the basis of relative conveyance across each cross-section. An

example of the resulting flow distribution estimates at a cross-section is shown on Figure 30. This

type of information has been produced for all the design events and has been provided to Council

in digital form for direct incorporation into their internal GIS.


Webb, McKeown & Associates Pty Ltd22032:MacRiverFSFinal.wpd:18August 2004 24

Table 12: Summary of Design Flood Levels

Chainage fromHawkesbury River

(m)

Location 500 Year ARI 200 Year ARI 100 Year ARI 50 Year ARI 20 Year ARI 5 Year ARI

Level

(mAHD)

Flow

(m3/s)

Level

(mAHD)

Flow

(m3/s)

Level

(mAHD)

Flow

(m3/s)

Level

(mAHD)

Flow

(m3/s)

Level

(mAHD)

Flow

(m3/s)

Level

(mAHD)

Flow

(m3/s)

1570 9.5 5497 8.0 4290 6.7 3430 5.6 2630 4.4 1810 3.2 753

3675 9.5 5500 8.0 4290 6.9 3430 6.1 2640 5.2 1820 3.7 753

4570 9.5 5500 8.0 4290 7.4 3430 6.5 2640 5.6 1820 3.9 753

6100 9.7 5500 8.8 4290 8.1 3440 7.2 2640 6.2 1830 4.4 754

8210 10.9 5510 9.9 4300 9.1 3440 8.3 2640 7.3 1820 5.5 755

9990 11.6 5470 10.6 4260 9.8 3420 9.0 2630 8.0 1810 6.2 752

11380 12.2 5470 11.2 4270 10.3 3420 9.4 2630 8.4 1810 6.5 752

14010 Wrights Ck 12.9 5200 11.9 4070 11.0 3260 10.1 2510 8.9 1740 7.0 718

16960 13.8 5180 12.7 4050 11.8 3250 10.8 2510 9.6 1740 7.6 717

19950 15.5 5070 14.3 3970 13.5 3190 12.5 2460 11.5 1710 8.9 704

22185 St Albans 16.7 5070 15.5 3970 14.6 3190 13.7 2460 12.6 1710 9.8 705

23330 17.1 5060 15.9 3970 15.0 3190 14.1 2460 13.0 1710 10.1 705

24380 17.3 5060 16.2 3960 15.3 3190 14.3 2460 13.2 1710 10.3 707

26280 17.4 5080 16.2 3980 15.4 3200 14.4 2470 13.3 1720 10.5 718

27270 18.0 4380 16.8 3430 15.9 2750 14.9 2130 13.8 1480 11.0 608

28110 18.2 4380 17.0 3430 16.1 2750 15.1 2130 13.9 1480 11.2 608

29490 18.7 4360 17.6 3410 16.7 2740 15.7 2120 14.4 1480 11.8 606

31280 Womerah Ck 19.3 4360 18.1 3420 17.2 2750 16.2 2120 15.0 1480 12.5 607

32800 19.8 4210 18.6 3300 17.7 2650 16.8 2050 15.5 1430 13.1 587



7.2.2 Provisional Flood Hazard and Hydraulic Categorisation

For the purposes of floodplain risk management in NSW the floodplain is broadly divided into one

of three Hydraulic categories (floodway, flood storage or flood fringe) and two Provisional Hazard

categories (Low or High). Further details of this process are outlined in the NSW Government’s

Floodplain Management Manual (January 2001, Reference 8).

Maps of the provisional hydraulic hazard (velocity x depth product) for the 100 Year ARI and

Extreme events are provided on Figures 31 and 32. For the purposes of the present study, the

provisional flood hazard has been determined at the model cross-sections in accordance with the

following criteria:

C High Flood Hazard: Assigned where the depth of flow or ‘velocity x depth’ product is

greater than one. The flow velocity used in the determination of the velocity x depth

product was the equivalent average velocity determined from the corresponding peak

discharge and local conveyance calculations across each cross-section.

C Low Flood Hazard: All other segments of the cross-section.

In view of the limited topographic data available, the conservative approach above was considered

appropriate given the significant depth of flow across the floodplain for the 100 Year ARI and

Extreme flood events and the one-dimensional flow behaviour of the system. The results indicate

that the Macdonald River floodplain is predominantly a high-hazard area for larger events. This

outcome is consistent with the confined nature of the floodplain and the relatively steep topography

bounding the floodplain along the lower Macdonald River.

The hydraulic categorisation was determined qualitatively based upon the available hydraulic and

survey information together with our knowledge of the Macdonald River catchment and experience

in similar rural to semi-rural floodplains. Due to the relatively confined nature of the floodplain, the

majority of the floodplain modelled for the present study conveys significant flow and functions

primarily as a ‘floodway’ as defined in the NSW Floodplain Management Manual (Reference 8).

In view of the linear nature of the flood behaviour and considering the limited survey data available,

the broad classification of ‘floodway’ is considered reasonable. This classification is made with an

acknowledgement that there may exist a limited area immediately adjacent to the floodway extent

that could be classed as ‘flood fringe’ where the depth of flow is less 0.5m. The exact delineation

of this hydraulic category can only be verified following detailed survey. Other areas subject to

backwater flooding from the Macdonald River have also been classed as ‘flood fringe’ in

accordance with Appendix G of Reference 8.

The constrained nature of the floodplain and the comparative volume of catchment runoff for larger

design events effectively limits the delineation of ‘flood storage’ for the Lower Macdonald floodplain.

Although the component of Flood Storage (as defined by the Manual) is likely to be significant over

the length of the Macdonald River floodplain, this particular component has been considered to be

incorporated within the area nominated as ‘floodway’ for the purposes of the present study. This

approach takes into account the available data throughout the area and the likely flood behaviour

of the system.



7.2.3 Provisional Categorisation of Flood Prone Land

Due to the limited availability of comprehensive survey information, detailed and precise category

mapping of the floodplain was not possible. However, following consideration of the likely flood

behaviour of the system and in view of the classifications discussed in Section 7.2.2, it is suggested

that the flood prone land within the detailed study area be provisionally categorised in accordance

with Table 13 and the following. A mapped representation of this categorisation is shown on Figure

33 for the 100 Year ARI event. It is important to acknowledge that the categories described in this

Section are only provisional pending further assessment and refinement as part of the subsequent

Floodplain Risk Management Study and Plan (FRMS&P).

A number of zones have been defined along the Macdonald River to better account for differences

in the flood behaviour within different reaches. For the purposes of categorising the 100 Year ARI

event in the lower-most reaches (Zones A and B), an allowance has been made for the influence

of backwater flooding due to events on the Hawkesbury River. For example, it is likely that the

depths will be high yet the flow velocities will be moderate, during backwater flooding of this region

especially when compared with typical velocities likely to be experienced further upstream. Hence,

an allowance has been made for the categorisation in this reach where the depths are between

0.5m and 1m. In contrast, Zones C and E represent reaches where the flow velocities are relatively

higher and hence anywhere where the depths are greater than 0.5m can be regarded as being High

Hazard Floodway. Zone B represents a transitional zone between Zones A and C. Zone D covers

a reach where there is a distinct change in waterway area and a corresponding decrease in

expected flow velocity for the 100 Year ARI event.

When interpreting this information, it should be noted that the due to the relatively confined nature

of the floodplain, the lower Macdonald River is likely to experience a significant range in flood levels

across different flood frequencies, particularly for the larger events. Accordingly, it is critical that

management and planning decisions also address the issues associated with large floods between

the 100 Year ARI event and the Extreme event. For the purposes of the present study, it is

suggested that the area of flood prone land between the 100 Year ARI and Extreme flood extents

be provisionally classified as Low Hazard Flood Fringe (refer to Table 13). The additional flood

risks associated with events of this magnitude will need to be developed and considered as part

of the Floodplain Risk Management Study and Plan (FRMS&P) for the Lower Macdonald River.

It should also be noted that the categorisation has been prepared following consideration of a

number of factors including the natural flood behaviour, modelling assumptions, available

topographic data and the types of future development likely occur within the floodplain. For

example, it is expected that any future development would be restricted to free-standing

developments of a rural nature, constructed in isolation. This would be typical of the existing types

of development currently found within the valley.



Table 13: 100 Year ARI Event - Provisional Flood Categorisation

Location(refer to

Figure 33)

ConditionsFlood

Category

Provisional

Hydraulic

Hazard

Comments

Zone A Flood Depth > 1.0m Floodway HighThis reach is subject to flooding from

both the Macdonald River catchment

and backwater from the Hawkesbury

River. The exact delineation between

'flood fringe' and 'floodway' is not

possible without detailed survey.

0.5m < Flood Depth < 1.0m Floodway Low

Flood Depth < 0.5mFlood

FringeLow

Zone B Flood Depth > 0.5m Floodway High


FringeLow

This classification can only be applied to

those areas which are immediately

adjacent to the 'floodway' area.

Zone C Flood Depth > 0.5m Floodway HighFor areas of the floodplain generally

bounded by St Albans Road and Settlers

Road.Flood Depth < 0.5m

(within 100 Year ARI flood

extent)

Flood

StorageHigh/Low



adjacent to the 'floodway' area above.

Flood Depth > 1mFlood

FringeHigh

There are numerous areas in this region

that will be subject to backwater flooding

from the Macdonald River. These are as

indicated on Figure 33.

Zone D Flood Depth > 1m Floodway High

Located approximately 1.7km upstream

of St Albans, this particular area exhibits

a large change in waterway area and a

corresponding decrease in flow velocity.0.5m < Flood Depth < 1m Floodway Low

Flood Depth < 0.5m


extent)

Flood

StorageLow

Zone E Flood Depth > 0.5m Floodway HighFor the reaches of the Macdonald River

upstream of Zone D and downstream of

the Womerah Creek junction.Flood Depth < 0.5m


extent)

Flood

StorageHigh/Low



adjacent to the 'floodway' area above.


FringeLow



adjacent to the 'floodway' area noted

above.



7.3 Comparison of the 100 Year ARI Design Event With the 1949 Flood

Given that the 100 Year ARI design event and the 1949 historical event are similar in magnitude

at St Albans, the estimated flood levels for the 100 Year ARI event were compared to available

observed levels along the Macdonald River. The corresponding peak flood height profiles are

presented on Figure 34. For completeness, the corresponding information for the March 1978

event is also included on the same plot.

An initial review of the historical data shown on Figure 34 indicates that there is a large degree of

uncertainty in the observed levels, with variations of up to 0.8m within the vicinity of St Albans and

corresponding discrepancies of approximately 1.5m at Wrights Creek. Furthermore, the observed

level of 14.2 mAHD just upstream of St Albans Commons is lower than any of the observed levels

at St Albans which range from 14.25 mAHD to 15.0 mAHD.

However, from a general perspective, Figure 34 shows that the estimated 100 Year ARI peak

height profile from St Albans to Wrights Creek either matches or slightly over-estimates the general

shape of the observed profile for the 1949 event. This trend lends confidence in the model results

obtained for the 100 Year ARI event which is a key event for planning purposes.

It is interesting to note that the model over-estimates the 1949 levels in the uppermost reaches

beyond St Albans. This behaviour is in contrast to the modelled behaviour for the March 1978

event where the model underestimated the observed levels in these locations. Although this

outcome justifies the adopted model calibration adopted to a certain extent, it serves to highlight

the degree of uncertainty present in the flood analysis undertaken for the Lower Macdonald River

floodplain. It is important that the interpretation of the design flood behaviour and selection of an

appropriate freeboard for planning purposes take these issues into account.



8. CONCLUSION

This Flood Study of the Macdonald River constitutes the first stage of the floodplain risk

management process for this catchment. The information contained herein is suitable for the

preparation of a subsequent Floodplain Risk Management Study and Plan.

Making best use of available information, numerical models to quantify the historical flood behaviour

of the catchment were calibrated and verified. In conjunction with a flood frequency analysis

undertaken using streamflow data recorded at St Albans, the calibrated numerical models were

used to quantify the design flood behaviour of the Lower Macdonald River floodplain. Information

defining the flood behaviour for design events up to the 500 year ARI and the Extreme event was

produced.

The analysis and review of historical information show that there is a degree of uncertainty in the

records of past flooding within the study area. Available evidence also suggests that the Macdonald

River is morphologically active, with the shape and form of the channel bed and overbank areas

undergoing significant change following successive floods between 1949 and 1955. These factors

should be taken into consideration when interpreting the results of this study during the preparation

of the Floodplain Risk Management Study and Plan for the Lower Macdonald floodplain.

In view of these uncertainties, it is recommended that the expected order of accuracy for the design

flood levels is generally be between ±0.3 m to ±0.5 m. In view of the good model calibration and

verification achieved in the immediate vicinity of St Albans, the expected level of accuracy would

be in the order of ±0.3 m at this location.



9. ACKNOWLEDGMENTS

This study was carried out by Webb, McKeown & Associates Pty Ltd and funded by Hawkesbury

City Council and the Department of Infrastructure, Planning and Natural Resources. The

assistance of the following in providing data and guidance to the study is gratefully acknowledged:

• Hawkesbury City Council staff and the Floodplain Management Committee,

• Department of Infrastructure, Planning and Natural Resources,

• Residents and landholders of the Macdonald River catchment.



10. REFERENCES

1. H M Henry

Catastrophic Channel Changes in the Macdonald Valley, New South Wales 1949-

1955

Journal & Proceedings, Royal Society of New South Wales, Vol. 110, pp. 1-16, 1977.

2. Public Works Department

Warragamba Dam Auxiliary Spillway EIS Flood Study

Webb, McKeown & Associates, October 1996

3. Australian Water and Coastal Studies Pty Ltd

Lower Hawkesbury River Flood Study

AWACS Report No. 94/29, 1997.

4. D H Pilgrim (Editor in Chief)

Australian Rainfall and Runoff - A Guide to Flood Estimation

Institution of Engineers, Australia, 1987.

5. DHI Water and Environment

Mike-11 Users Guide and Reference Manual V2003

6. M A Walsh, D H Pilgrim and I Cordery

Initial Losses for Design Flood Estimation in New South Wales

International Hydrology and Water Resources Symposium Proceedings, pp283-288, 1991.

7. G Kuczera

FLIKE Version 4.50 Software Manual

Department of Civil, Surveying and Environmental Engineering, University of Newcastle,

2001.

8. New South Wales Government

Floodplain Management Manual: The management of flood liable land

January 2001.

FIGURESFIGURES

306000

306000

308000

308000

310000

310000

312000

312000

314000

314000

316000

316000

6306

000

6306

000

6308

000

6308

000

6310

000

6310

000

6312

000

6312

000

6314

000

6314

000

6316

000

6316

000

6318

000

6318

000

FIGURE 1STUDY AREA

0 30 km

¯

Study Catchment

Detailed Study Area

St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

!.

!.

!.

!.

!.

!.

!.

306000

306000

308000

308000

310000

310000

312000

312000

314000

314000

6306

000

6306

000

6308

000

6308

000

6310

000

6310

000

6312

000

6312

000

6314

000

6314

000

6316

000

6316

000

6318

000

6318

000

FIGURE 2AVAILABLE SURVEY DATA

!. PWD Hydrosurvey

GPS Survey Data

St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

500 0 500 1,000 1,500 2,000250

Metres

#

#

#

#

#

#

#

#

BALA

WOMERAH

LAMBTON

MT CALORE

ST ALBANS

PUTTY (THE GIBBA)

PUTTY FOREST (3WAYS)

COLO HEIGHTS COMPOSITE

ST ALBANS (MOGO CREEK)

HOWES VALLEY (KINDARUN)

HOWES VALLEY (OWENSDALE)

HOWES VALLEY (NOISY POINT)

PEATS RIDGE (WARATAH ROAD)

LOWER PORTLAND (ORANGE GROVE)

MANGROVE MOUNTAIN (DUBBO GULLY)

WISEMANS FERRY (OLD POST OFFICE)

PUTTY POST OFFICE (PUTTY COMPOSITE)

270000

270000

280000

280000

290000

290000

300000

300000

310000

310000

320000

320000

330000

330000

6290

000

6300

000

6300

000

6310

000

6310

000

6320

000

6320

000

6330

000

6330

000

6340

000

6340

000

6350

000

6350

000

6360

000

6360

000

6370

000

6370

000

6380

000

6380

000

FIGURE 3LOCATIONS OF RAINFALL STATIONS

Rainfall Stations# Pluviograph

Daily Read

Hawkesbury River

Webbs Ck Wrights Ck

Macdonald R

iver

0 4 8 12 16Km

BIG_BOREE

MELON_CK

BOGGY

LOWER_MOGO

PALONA_CK

MALONG

NOISY_PT

WRIGHTS_CK

LOWER_YENGO

UPPER_HOWES

UPPER_MOGO

UPPER_MAC

APPLETREE

REEDY_CK

MARLO_CK

UPPER_YENGO

BURROWELL_CK

CALORIE_CK

TOORWAI_CK

WOMERAH_CK

PALOMORANG

MT_YENGO

WELLUMS_CK

THOMPSON

BAILEY_CK

LOWER_HOWES

FORBES_CK

LOWER_MAC

UPPER_ST_ALBANS

FLEMINGS

ST_ALBANS

COLO_CK

MIDDLE_MAC

UPPER_COMM

270000

270000

280000

280000

290000

290000

300000

300000

310000

310000

320000

320000

330000

330000

6300

000

6300

000

6310

000

6310

000

6320

000

6320

000

6330

000

6330

000

6340

000

6340

000

6350

000

6350

000

6360

000

6360

000

6370

000

6370

000

6380

000

6380

000

FIGURE 4WBNM MODEL LAYOUT

WBNM Sub-Areas Hawkesbury River

Webbs Ck Wrights Ck

Macdonald R

iver

0 4 8 12 16Km

FIGURE 5

HISTORICAL RAINFALL DATA

MARCH 1978 EVENT

PUTTY POST OFFICEPUTTY (THE GIBBA)

200

200

250

300

300

250

200

150

150

200

187

286

118

ISOHYETAL MAP96HRS FROM 0900 18/3/78

SOURCE:WARRAGAMBA DAM AUXILLARY SPILLWAYEIS FLOOD STUDY - PART B (1996)

(REFERENCE 2)

Ra

infa

ll(m

m)

Ra

infa

ll(m

m)

250

250

FIGURE 6


AUGUST 1990 EVENT

MT CALOREDUBBO GULLY

Rain

fall

(mm

)

WOMERAHNOISY POINT

Rain

fall

(mm

)

Rain

fall

(mm

)R

ain

fall

(mm

)

150

150

100

100

146.50

136.50

119

141 153

163

102.5

82

97

71



(REFERENCE 2)

FIGURE 7


APRIL 1988 EVENT

100

100

150

150

50

50

20

20

120

38


Ra

infa

ll(m

m)

Ra

infa

ll(m

m)

PEATS RIDGECOLO HEIGHTS


(REFERENCE 2)

FIGURE 8


AUGUST 1986 EVENT

COLO HEIGHTS

250

250

300

300

200200

150

150


Ra

infa

ll(m

m)


(REFERENCE 2)

FIGURE 9

Discharge(m3/s)

Tim

e(

hours

from

0900

18/3

/1978

)

FLOW HYDROGRAPHS

MARCH 1978 CALIBRATION EVENT

FIGURE 10

FLOW HYDROGRAPHS

AUGUST 1990 VERIFICATION EVENT

Tim

e(

hours

from

0000

31/0

7/9

0)

Discharge(m3/s)

FIGURE 11

FLOW HYDROGRAPHS

APRIL 1988 EVENT

Tim

e(

hours

from

0900

27/4

/1988

)

Discharge(m3/s)

FIGURE 12

FLOW HYDROGRAPHS


Tim

e(

hours

from

0000

4/8

/86

)

Discharge(m3/s)

8420 m

0 m

31230 m

9470 m

29125 m

21420 m

22810 m

24590 m

4690 m

18790 m

3310 m

10615 m

1520 m

26700 m

6520 m

12850 m

1260 m

5530 m

15840 m

0 m

305000

305000

310000

310000

315000

315000

6305

000

6310

000

6310

000

6315

000

6315

000

FIGURE 13MIKE11 MODEL LAYOUT

Cross-section & MIKE11 ChainageE Lateral Inflow

St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

500 0 500 1,000 1,500 2,000

Metres

EE

E

E

E E

E

E

FIG

UR

E 14

CO

MP

AR

ISO

N W

ITH

AV

AIL

AB

LE

DA

TA

M

AR

CH

1978 CA

LIB

RA

TIO

N E

VE

NT

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

0 5000 10000 15000 20000 25000 30000

Chainage from Hawkesbury River Confluence (m)

Hei

gh

t (m

AH

D)

MIKE11 Peak Flood Profile

MIKE11 100 Year Event

Observed Level (Source: HCC Council Profile 1984)

Observed Level (Source: 2003 GPS Field Survey)

Location Identifiers

St.

Alb

ans

Com

mon

St A

lban

s

Wrig

hts

Cre

ek

FIGURE 15STAGE HYDROGRAPHS AT ST ALBANS


1

2

3

4

5

6

7

8

9

10

11

12

18/03/19780:00

19/03/19780:00

20/03/19780:00

21/03/19780:00

22/03/19780:00

23/03/19780:00

24/03/19780:00

25/03/19780:00

Hei

ght (

m A

HD

)

MIKE11 Results

Observed Stage (Station 212010)

FIGURE 16FLOW HYDROGRAPHS AT ST ALBANS


0

100

200

300

400

500

600

700

800

900

1000

18/03/19780:00

19/03/19780:00

20/03/19780:00

21/03/19780:00

22/03/19780:00

23/03/19780:00

24/03/19780:00

25/03/19780:00

MIKE11 Results

Estimated Flow (Station 212010)

Flow

(m3 /s

)

FIGU

RE

17PEA

K H

EIGH

T PRO

FILEA

UG

UST 1990 VER

IFICA

TION

EVENT

3

4

5

6

7

8

9

10

11

12

13

0 5000 10000 15000 20000 25000 30000


Hei

ght (

m A

HD

)

MIKE11 Peak Height Flood ProfileObserved Level (Source: DIPNR Station 212010)Location Identifiers

St.

Alb

ans

Com

mon

St A

lban

s

Wrig

hts

Cre

ek

FIGURE 18STAGE HYDROGRAPHS AT ST ALBANS


1

2

3

4

5

6

7

8

9

1/08/1990 0:00 2/08/1990 0:00 3/08/1990 0:00 4/08/1990 0:00

Hei

ght

(m A

HD

)

MIKE11 Results

Observed Stage (Station 212010)

FIGURE 19FLOW HYDROGRAPHS AT ST ALBANS


0

100

200

300

400

500

1/08/1990 0:00 2/08/1990 0:00 3/08/1990 0:00 4/08/1990 0:00

MIKE11 Results

Observed Flow (Station 212010)

Flow

(m3 /s

)

LP3 fit (gauge data only)

90% Conf. Limit

90% Conf.

Data Point

LP3 fit (including 1949 event)

90% Conf. Limit

90% Conf.

Data Point

FIGURE 20

FLOOD FREQUENCY

ANALYSES

1949 Event

FIL

E>

J:\

JO

BS

\22

03

2\A

DM

IN\F

IGU

RE

S\ffa

.cd

rD

AT

E>

Fe

bru

ary

20

04

WBNM Flow Estimates(adjusted for annual series comparison)

WBNM Flow Estimates(adjusted for annual series comparison)

FIG

UR

E 21

PE

AK

HE

IGH

T P

RO

FIL

ES

DE

SIG

N F

LO

OD

EV

EN

TS

MA

CD

ON

AL

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IVE

R

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

0 5000 10000 15000 20000 25000 30000


Hei

gh

t (m

AH

D)

500 Year ARI 200 Year ARI

100 Year ARI 50 Year ARI

5 Year ARI Extreme Event


St.

Alb

ans

Com

mon

St A

lban

s

Wri

ghts

Cre

ek

9.5

17.3

9.7

12.2

18

11.6

10.9

12.9

17.1

18.2

16.7

18.7

15.5

19.3

17.4

13.8

19.8

12.9

9.5

12.9

9.5

500 Year ARI Peak Flood Height (m AHD)

St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

FIGURE 22DESIGN FLOOD HEIGHTS

500 YEAR ARI EVENT

NOTE: Inundation Extents Not Shown

500 0 500 1,000 1,500Metres

8

16.2

17

9.9

8.8

11.1

10.6

11.9

15.9

11.8

15.5

17.6

14.3

18.1

12.7

16.818.6

16.2

88

11.8



St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River


200 YEAR ARI EVENT

500 0 500 1,000 1,500Metres

15.3

6.711

159.1

7.4

6.9

9.8

8.1

10.3

16.7

16.1

17.2

13.5

15.4

11.8

15.9

14.6

17.7

11

11


NOTE: Extents shown at each location are indicative only and may be limited by limit of available survey. The actual extent should be confirmed with detailed local survey.

St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

FIGURE 24DESIGN FLOOD HEIGHTS AND EXTENTS

100 YEAR ARI EVENT

500 0 500 1,000 1,500Metres

9

5.6

14.36.5

10

6.1

9.4

8.3

7.2

10.1

14.1

15.1

13.7

15.7

12.5

16.2

14.4

10.8

14.916.8

10



St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River


50 YEAR ARI EVENT

500 0 500 1,000 1,500Metres

8

13.2

137.3

8.4

8.9

4.4

5.25.6

6.2

15

9.6

14.4

11.5

13.3

13.815.5

12.6

13.9

8.9

8.9



St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

FIGURE 26DESIGN FLOOD LEVELS AND EXTENTS

20 YEAR ARI EVENT

500 0 500 1,000 1,500Metres

7

3.9

12.14.7

4.4

7.4

6.3

7.9

5.2

11.9

8.6

12.711

.6

13.2

10.6

13.8

12.2

12.614.3

7.9

7.9



St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River


10 YEAR ARI EVENT

500 0 500 1,000 1,500Metres

7

3.2

10.33.9

3.7

6.5

6.2

5.5

9.8

4.4

8.911

10.1

7.6

11.2

11.812.5

10.5

13.1

7

7



St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River


5 YEAR ARI EVENT

500 0 500 1,000 1,500Metres

20.4

20

16.3

19.6

21.9

21.3

22.5

18.4

20.3

16.6

20.922.9

16.316.3

16.3

16.3

16.316.3

16.3

16.3

16.3

Extreme Event Peak Flood Height (m AHD)


St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

FIGURE 29DESIGN FLOOD HEIGHTS AND EXTENTS

EXTREME FLOOD EVENT

500 0 500 1,000 1,500Metres

9

8.4

1.57

6.34.9

8.7

3.5

4.74.2

4.4

3.3

6.21.95.2

3.1

3.7

1.2

2.6 2.2 0.2

1.66.3

% Flow Distribution Across Cross-section

Macdonald River

FIGURE 30EXAMPLE OF FLOW DISTRIBUTION

AT MODEL CROSS-SECTIONS100 YEAR ARI EVENT

10 0 10 20 30 40 50Metres

High Flood Hazard

Low Flood Hazard


St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

FIGURE 31PROVISIONAL FLOOD HAZARD

AT CROSS-SECTIONS100 YEAR ARI EVENT

500 0 500 1,000 1,500Metres

High Flood Hazard

Low Flood Hazard


St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

FIGURE 32PROVISIONAL FLOOD HAZARD

AT CROSS-SECTIONSEXTREME FLOOD EVENT

500 0 500 1,000 1,500Metres

NOTE: The information shown should be interpreted in conjunction with Table 13 and Section 7 of the Lower Macdonald Flood Study Report.

St Albans

Hawkesbury River

Webbs Ck

Wrights Ck

Womerah Ck

Macdonald River

FIGURE 33CATEGORISATION OF FLOOD PRONE LAND

Extent of Modelling

Outside of Detailed Study Area



Extent of Modelling

A

B

C

D

E

LEGENDIndicative Extent of Flood Fringe

Indicative Extent of Floodway

Zone (Refer to Table 13)A

NOTE: The exact delineation between 'flood fringe' and 'floodway' in this area is subject to detailed survey.

0 500 1,000 1,500 2,000250Metres

FIG

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PE

AK

HE

IGH

T P

RO

FIL

ES

MA

CD

ON

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R 100 Y

EA

R A

RI D

ES

IGN

EV

EN

T A

ND

1949 HIS

TO

RIC

AL

EV

EN

TS

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

0 5000 10000 15000 20000 25000 30000


Hei

gh

t (m

AH

D)

100 Year ARI Design Event MIKE 11 Peak Flood Profile

1978 Event MIKE11 Peak Flood Profile

1949 Observed Levels

March 1978 Observed Level (Source: HCC)

March 1978 Observed Level (Source: GPS Survey)

Location Identifiers St.

Alb

ans

Com

mon

St A

lban

s

Wri

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Cre

ek

APPENDIX A:APPENDIX A: GLOSSARY OF FLOOD RELATED TERMS


Webb, McKeown & Associates Pty Ltd22032:MacRiverFSFinal.wpd:18 August, 2004 A1

APPENDIX A: GLOSSARY OF TERMS

Annual ExceedanceProbability (AEP)

The chance of a flood of a given or larger size occurring in any one year, usuallyexpressed as a percentage. For example, if a peak flood discharge of 500 m 3/s hasan AEP of 5%, it means that there is a 5% chance (that is one-in-20 chance) of apeak flood discharge of 500 m3/s or larger occurring in any one year (see averagerecurrence interval).

Australian Height Datum(AHD)

A common national surface level datum approximately corresponding to mean sealevel.

Average Annual Damage(AAD)

Depending on its size (or severity), each flood will cause a different amount of flooddamage to a flood prone area. AAD is the average damage per year that wouldoccur in a nominated development situation from flooding over a very long periodof time.

Average RecurrenceInterval (ARI)

The long term average number of years between the occurrence of a flood as bigas, or larger than, the selected event. For example, floods with a discharge asgreat as, or greater than, the 20 year ARI flood event will occur on average onceevery 20 years. ARI is another way of expressing the likelihood of occurrence of aflood event.

catchment The land area draining through the main stream, as well as tributary streams, to aparticular site. It always relates to an area above a specific location.

development Is defined in Part 4 of the Environmental Planning and Assessment Act (EP&A Act).

infill development: refers to the development of vacant blocks of land that aregenerally surrounded by developed properties and is permissible under the currentzoning of the land. Conditions such as minimum floor levels may be imposed oninfill development.

new development: refers to development of a completely different nature to thatassociated with the former land use. For example, the urban subdivision of an areapreviously used for rural purposes. New developments involve rezoning andtypically require major extensions of existing urban services, such as roads, watersupply, sewerage and electric power.

redevelopment: refers to rebuilding in an area. For example, as urban areas age,it may become necessary to demolish and reconstruct buildings on a relatively largescale. Redevelopment generally does not require either rezoning or majorextensions to urban services.

discharge The rate of flow of water measured in terms of volume per unit time, for example,cubic metres per second (m3/s). Discharge is different from the speed or velocityof flow, which is a measure of how fast the water is moving for example, metres persecond (m/s).

flash flooding Flooding which is sudden and unexpected. It is often caused by sudden local ornearby heavy rainfall. Often defined as flooding which peaks within six hours of thecausative rain.

flood Relatively high stream flow which overtops the natural or artificial banks in any partof a stream, river, estuary, lake or dam, and/or local overland flooding associatedwith major drainage before entering a watercourse, and/or coastal inundationresulting from super-elevated sea levels and/or waves overtopping coastlinedefences excluding tsunami.

flood fringe areas The remaining area of flood prone land after floodway and flood storage areas havebeen defined.



flood liable land Is synonymous with flood prone land (i.e. land susceptible to flooding by theprobable maximum flood (PMF) event). Note that the term flood liable land nowcovers the whole of the floodplain, not just that part below the flood planning level,as indicated in the 1986 Floodplain Development Manual (see flood planning area).

floodplain Area of land which is subject to inundation by floods up to and including theprobable maximum flood event, that is, flood prone land.

Flood Planning Levels(FPLs)

The combination of flood levels and freeboards selected for planning purposes, asdetermined in floodplain risk management studies and incorporated in floodplainrisk management plans. The concept of flood planning levels supersedes the“standard flood event” of the first edition of this manual.

flood prone land Is land susceptible to flooding by the Probable Maximum Flood (PMF) event. Floodprone land is synonymous with flood liable land.

flood risk Potential danger to personal safety and potential damage to property resulting fromflooding. The degree of risk varies with circumstances across the full range offloods. Flood risk in this manual is divided into 3 types, existing, future andcontinuing risks. They are described below.

existing flood risk: the risk a community is exposed to as a result of its locationon the floodplain.

future flood risk: the risk a community may be exposed to as a result of newdevelopment on the floodplain.

continuing flood risk: the risk a community is exposed to after floodplain riskmanagement measures have been implemented. For a town protected by levees,the continuing flood risk is the consequences of the levees being overtopped. Foran area without any floodplain risk management measures, the continuing flood riskis simply the existence of its flood exposure.

flood storage areas Those parts of the floodplain that are important for the temporary storage offloodwaters during the passage of a flood. The extent and behaviour of floodstorage areas may change with flood severity, and loss of flood storage canincrease the severity of flood impacts by reducing natural flood attenuation. Hence,it is necessary to investigate a range of flood sizes before defining flood storageareas.

floodway areas Those areas of the floodplain where a significant discharge of water occurs duringfloods. They are often aligned with naturally defined channels. Floodways areareas that, even if only partially blocked, would cause a significant redistribution offlood flows, or a significant increase in flood levels.

hazard A source of potential harm or a situation with a potential to cause loss. In relationto this manual the hazard is flooding which has the potential to cause damage tothe community. Definitions of high and low hazard categories are provided in theFloodplain Management Manual.

hydraulics Term given to the study of water flow in waterways; in particular, the evaluation offlow parameters such as water level and velocity.

hydrograph A graph which shows how the discharge or stage/flood level at any particularlocation varies with time during a flood.

hydrology Term given to the study of the rainfall and runoff process; in particular, theevaluation of peak flows, flow volumes and the derivation of hydrographs for arange of floods.

local overland flooding Inundation by local runoff rather than overbank discharge from a stream, river,estuary, lake or dam.

local drainage Are smaller scale problems in urban areas. They are outside the definition of majordrainage in this glossary.



mainstream flooding Inundation of normally dry land occurring when water overflows the natural orartificial banks of a stream, river, estuary, lake or dam.

major drainage Councils have discretion in determining whether urban drainage problems areassociated with major or local drainage. For the purpose of this manual majordrainage involves:• the floodplains of original watercourses (which may now be piped,

channelised or diverted), or sloping areas where overland flows developalong alternative paths once system capacity is exceeded; and/or

• water depths generally in excess of 0.3 m (in the major system designstorm as defined in the current version of Australian Rainfall andRunoff). These conditions may result in danger to personal safety andproperty damage to both premises and vehicles; and/or

• major overland flow paths through developed areas outside of defineddrainage reserves; and/or

• the potential to affect a number of buildings along the major flow path.

mathematical/computermodels

The mathematical representation of the physical processes involved in runoffgeneration and stream flow. These models are often run on computers due to thecomplexity of the mathematical relationships between runoff, stream flow and thedistribution of flows across the floodplain.

peak discharge The maximum discharge occurring during a flood event.

Probable Maximum Flood(PMF)

The largest flood that could conceivably occur at a particular location, usuallyestimated from probable maximum precipitation. Generally, it is not physically oreconomically possible to provide complete protection against this event. The PMFdefines the extent of flood prone land, that is, the floodplain. The extent, nature andpotential consequences of flooding associated with the PMF event should beaddressed in a Floodplain Risk Management study.

Probable MaximumPrecipitation (PMP)

The greatest depth of precipitation for a given duration meteorologically possibleover a given size storm area at a particular location at a particular time of the year,with no allowance made for long-term climatic trends (World MeteorologicalOrganisation, 1986). It is the primary input to the estimation of the probablemaximum flood.

probability A statistical measure of the expected change of flooding (see annual exceedanceprobability).

risk Chance of something happening that will have an impact. It is measured in termsof consequences and likelihood. In the context of the manual it is the likelihood ofconsequences arising from the interaction of floods, communities and theenvironment.

runoff The amount of rainfall which actually ends up as streamflow, also known as rainfallexcess.

stage Equivalent to “water level”. Both are measured with reference to a specifieddatum.

stage hydrograph A graph that shows how the water level at a particular location changes withtime during a flood. It must be referenced to a particular datum.

survey plan A plan prepared by a registered surveyor.

water surface profile A graph showing the flood stage at any given location along a watercourse at aparticular time.

wind fetch The horizontal distance in the direction of wind over which wind waves aregenerated.

APPENDIX B:APPENDIX B: PUBLISHED GEOMORPHOLOGICAL ANALYSIS OF MACDONALD RIVER

APPENDIX C:APPENDIX C: PHOTOGRAPHS OF HISTORICAL FLOOD LEVEL SURVEY SITES

FIG

UR

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1O

BS

ER

VE

D F

LO

OD

HE

IGH

TS

LO

NG

ITU

DIN

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PR

OF

ILE

OF

MA

CD

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4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

0 5000 10000 15000 20000 25000 30000


Hei

gh

t (m

AH

D)

100 Year ARI Design Event MIKE 11 Peak Flood Profile

1978 Event MIKE11 Peak Flood Profile

1949 Observed Levels

March 1978 Observed Level (Source: HCC)

March 1978 Observed Level (Source: GPS Survey)


St.

Alb

ans

Com

mon

St A

lban

s

Wri

ghts

Cre

ek

HCC Pt 441

HCC Pt 549

HCC Pt 1000

HCC Pt 151

HCC Pt 503

HCC Pt 526

HCC Pt 108

HCC Pt 105

HCC Pt 525

Point Number 1000As reported by Joyce Steptoe who remembers as a child in 1949 stepping out onepace to be in the waters of the ‘49 flood. This is only approximately 200 metresupstreamoftheSt.AlbansPub.Co-ordinates;E 310700,N6314250

1949RL 15.09

Point Number 5261949 Flood came to the bottom of the window sill on Cottage. Source Mrs Jord

from same property

RL 14.18

Point Number 525Change of grade near fence.

RL 14.18

RL 13.213

RL13.213

Point Number 525Change of grade near fence.

Point Number 503

Point Number 503

Point Number 503

Point Number 5031949 Flood came to the milk line in the old dairy. Source Ray Morris, owner.

Point Number 503View through dairy door to property’s homestead

Point Number 150Base Station “H” RL 12.437

Floods reached floor level of this old shed

RL 10.596Presumedto be

1978

Point Number 150Source Mrs L. Bailey (45682106)

Point Number 150

Point Number 150

APPENDIX D:APPENDIX D: DESIGN FLOOD RESULTS

APPENDIX D: DESIGN FLOOD RESULTS Lower Macdonald River Flood Study

River name Chainage from MIKE11 500 Year ARI 200 Year ARIHawkesbury River (m) Chainage (m) Flood Peak

(mAHD)Peak Discharge

(m3/s) Peak Velocity (m/s)Flood Peak


(m3/s) Peak Velocity (m/s)

MACDONALD RIVER 32800 0 19.8 4207 2.9 18.6 3299 2.7MACDONALD RIVER 32705 95 19.7 4207 2.8 18.6 3299 2.6MACDONALD RIVER 32610 190 19.7 4207 2.7 18.5 3299 2.5MACDONALD RIVER 32515 285 19.6 4207 2.6 18.5 3299 2.4MACDONALD RIVER 32420 380 19.6 4207 2.5 18.5 3299 2.4MACDONALD RIVER 32325 475 19.6 4207 2.5 18.4 3299 2.3MACDONALD RIVER 32230 570 19.5 4207 2.4 18.4 3299 2.2MACDONALD RIVER 32135 665 19.5 4207 2.3 18.4 3299 2.1MACDONALD RIVER 32040 760 19.5 4207 2.2 18.3 3299 2.1MACDONALD RIVER 31945 855 19.4 4206 2.2 18.3 3299 2.0MACDONALD RIVER 31850 950 19.4 4206 2.1 18.3 3299 1.9MACDONALD RIVER 31755 1045 19.4 4206 2.0 18.3 3299 1.9MACDONALD RIVER 31660 1140 19.4 4206 2.0 18.2 3299 1.8MACDONALD RIVER 31565 1235 19.4 4206 1.9 18.2 3299 1.8MACDONALD RIVER 31470 1330 19.3 4282 1.9 18.2 3356 1.8MACDONALD RIVER 31375 1425 19.3 4360 1.9 18.2 3416 1.7MACDONALD RIVER 31280 1520 19.3 4360 1.8 18.1 3416 1.7MACDONALD RIVER 31180.56 1619.44 19.3 4359 1.8 18.1 3416 1.7MACDONALD RIVER 31081.11 1718.89 19.2 4359 1.8 18.1 3415 1.7MACDONALD RIVER 30981.67 1818.33 19.2 4358 1.9 18.1 3415 1.7MACDONALD RIVER 30882.22 1917.78 19.2 4358 1.9 18.0 3415 1.7MACDONALD RIVER 30782.78 2017.22 19.1 4358 1.9 18.0 3414 1.7MACDONALD RIVER 30683.33 2116.67 19.1 4357 1.9 18.0 3414 1.7MACDONALD RIVER 30583.89 2216.11 19.1 4357 1.9 17.9 3414 1.7MACDONALD RIVER 30484.44 2315.56 19.1 4357 1.9 17.9 3414 1.7MACDONALD RIVER 30385 2415 19.0 4357 1.9 17.9 3414 1.7MACDONALD RIVER 30285.56 2514.44 19.0 4357 1.9 17.8 3413 1.7MACDONALD RIVER 30186.11 2613.89 19.0 4357 1.9 17.8 3413 1.7MACDONALD RIVER 30086.67 2713.33 18.9 4356 1.9 17.8 3413 1.7MACDONALD RIVER 29987.22 2812.78 18.9 4356 1.9 17.7 3413 1.7MACDONALD RIVER 29887.78 2912.22 18.9 4356 1.9 17.7 3413 1.7MACDONALD RIVER 29788.33 3011.67 18.8 4356 1.9 17.7 3413 1.7MACDONALD RIVER 29688.89 3111.11 18.8 4356 1.9 17.6 3413 1.7MACDONALD RIVER 29589.44 3210.56 18.8 4356 1.9 17.6 3413 1.8MACDONALD RIVER 29490 3310 18.7 4355 1.9 17.6 3413 1.8MACDONALD RIVER 29391.43 3408.57 18.7 4355 1.9 17.5 3412 1.8MACDONALD RIVER 29292.86 3507.14 18.7 4355 1.9 17.5 3412 1.8MACDONALD RIVER 29194.29 3605.71 18.6 4355 1.9 17.5 3412 1.8MACDONALD RIVER 29095.71 3704.29 18.6 4355 1.9 17.4 3412 1.8MACDONALD RIVER 28997.14 3802.86 18.6 4355 1.9 17.4 3412 1.8MACDONALD RIVER 28898.57 3901.43 18.5 4354 1.9 17.4 3412 1.8MACDONALD RIVER 28800 4000 18.5 4354 1.9 17.3 3412 1.8MACDONALD RIVER 28701.43 4098.57 18.4 4354 1.9 17.3 3412 1.8MACDONALD RIVER 28602.86 4197.14 18.4 4354 2.0 17.2 3412 1.8MACDONALD RIVER 28504.29 4295.71 18.4 4354 2.0 17.2 3412 1.8MACDONALD RIVER 28405.71 4394.29 18.3 4354 2.0 17.2 3411 1.9MACDONALD RIVER 28307.14 4492.86 18.3 4354 2.0 17.1 3411 1.9MACDONALD RIVER 28208.57 4591.43 18.3 4365 2.0 17.1 3420 1.9MACDONALD RIVER 28110 4690 18.2 4377 2.0 17.0 3428 1.9MACDONALD RIVER 28016.67 4783.33 18.2 4377 2.0 17.0 3428 1.9MACDONALD RIVER 27923.33 4876.67 18.2 4376 2.0 17.0 3428 1.8MACDONALD RIVER 27830 4970 18.1 4376 1.9 16.9 3428 1.8MACDONALD RIVER 27736.67 5063.33 18.1 4376 1.9 16.9 3428 1.8MACDONALD RIVER 27643.33 5156.67 18.1 4377 1.9 16.9 3428 1.8MACDONALD RIVER 27550 5250 18.0 4377 1.9 16.9 3428 1.8MACDONALD RIVER 27456.67 5343.33 18.0 4377 1.9 16.8 3428 1.7MACDONALD RIVER 27363.33 5436.67 18.0 4377 1.9 16.8 3428 1.7MACDONALD RIVER 27270 5530 18.0 4377 2.0 16.8 3429 1.8MACDONALD RIVER 27171 5629 17.9 4377 2.0 16.8 3429 1.8MACDONALD RIVER 27072 5728 17.8 4726 2.2 16.7 3702 1.9MACDONALD RIVER 26973 5827 17.7 5086 2.4 16.6 3986 2.1MACDONALD RIVER 26874 5926 17.7 5085 2.4 16.5 3985 2.2MACDONALD RIVER 26775 6025 17.6 5085 2.4 16.5 3985 2.2MACDONALD RIVER 26676 6124 17.6 5084 2.4 16.4 3984 2.2MACDONALD RIVER 26577 6223 17.5 5084 2.5 16.4 3983 2.2MACDONALD RIVER 26478 6322 17.5 5083 2.5 16.3 3983 2.3MACDONALD RIVER 26379 6421 17.4 5082 2.5 16.3 3982 2.3MACDONALD RIVER 26280 6520 17.4 5082 2.6 16.2 3981 2.5MACDONALD RIVER 26180 6620 17.4 5081 2.3 16.2 3981 2.1MACDONALD RIVER 26080 6720 17.3 5080 2.2 16.2 3980 2.0MACDONALD RIVER 25980 6820 17.3 5080 2.0 16.2 3980 1.8MACDONALD RIVER 25880 6920 17.3 5079 1.8 16.2 3979 1.7MACDONALD RIVER 25780 7020 17.3 5078 1.7 16.2 3978 1.6MACDONALD RIVER 25680 7120 17.3 5077 1.6 16.2 3977 1.4MACDONALD RIVER 25580 7220 17.3 5075 1.5 16.2 3976 1.3MACDONALD RIVER 25480 7320 17.3 5074 1.4 16.2 3976 1.3MACDONALD RIVER 25380 7420 17.3 5073 1.3 16.2 3975 1.2MACDONALD RIVER 25280 7520 17.3 5071 1.2 16.2 3974 1.1MACDONALD RIVER 25180 7620 17.3 5070 1.1 16.2 3973 1.0MACDONALD RIVER 25080 7720 17.3 5068 1.1 16.2 3971 1.0MACDONALD RIVER 24980 7820 17.3 5067 1.0 16.2 3970 0.9MACDONALD RIVER 24880 7920 17.3 5065 1.0 16.2 3969 0.9MACDONALD RIVER 24780 8020 17.3 5064 1.0 16.2 3968 1.0MACDONALD RIVER 24680 8120 17.3 5063 1.1 16.2 3966 1.1MACDONALD RIVER 24580 8220 17.3 5062 1.2 16.2 3965 1.2MACDONALD RIVER 24480 8320 17.3 5061 1.3 16.2 3965 1.3MACDONALD RIVER 24380 8420 17.3 5059 1.4 16.2 3964 1.4MACDONALD RIVER 24284.55 8515.45 17.3 5058 1.0 16.2 3963 1.0MACDONALD RIVER 24189.09 8610.91 17.3 5057 0.9 16.1 3962 0.9MACDONALD RIVER 24093.64 8706.36 17.3 5056 0.9 16.1 3961 0.9MACDONALD RIVER 23998.18 8801.82 17.3 5055 1.0 16.1 3960 0.9MACDONALD RIVER 23902.73 8897.27 17.3 5054 1.0 16.1 3960 0.9MACDONALD RIVER 23807.27 8992.73 17.2 5053 1.1 16.1 3959 1.0MACDONALD RIVER 23711.82 9088.18 17.2 5052 1.2 16.1 3958 1.1MACDONALD RIVER 23616.36 9183.64 17.2 5052 1.3 16.1 3958 1.2MACDONALD RIVER 23520.91 9279.09 17.2 5052 1.4 16.0 3957 1.3MACDONALD RIVER 23425.45 9374.55 17.1 5051 1.6 16.0 3957 1.5MACDONALD RIVER 23330 9470 17.1 5063 1.7 15.9 3965 1.6MACDONALD RIVER 23237 9563 17.0 5074 1.8 15.9 3974 1.6MACDONALD RIVER 23144 9656 17.0 5074 1.8 15.9 3973 1.6MACDONALD RIVER 23051 9749 17.0 5073 1.8 15.8 3973 1.6


MACDONALD RIVER 22958 9842 17.0 5073 1.8 15.8 3973 1.6MACDONALD RIVER 22865 9935 16.9 5073 1.8 15.8 3972 1.7MACDONALD RIVER 22772 10028 16.9 5073 1.8 15.8 3972 1.7MACDONALD RIVER 22679 10121 16.9 5072 1.8 15.7 3972 1.7MACDONALD RIVER 22586 10214 16.8 5072 1.8 15.7 3972 1.7MACDONALD RIVER 22493 10307 16.8 5072 1.8 15.7 3972 1.7MACDONALD RIVER 22400 10400 16.8 5072 1.9 15.6 3971 1.7MACDONALD RIVER 22328.33 10471.67 16.7 5071 1.9 15.6 3971 1.7MACDONALD RIVER 22256.67 10543.33 16.7 5071 1.9 15.6 3971 1.8MACDONALD RIVER 22185 10615 16.7 5071 2.0 15.5 3971 1.8MACDONALD RIVER 22090 10710 16.6 5071 2.0 15.5 3971 1.8MACDONALD RIVER 21995 10805 16.6 5070 2.0 15.5 3970 1.8MACDONALD RIVER 21900 10900 16.6 5070 2.0 15.4 3970 1.9MACDONALD RIVER 21802.5 10997.5 16.5 5070 2.0 15.4 3970 1.9MACDONALD RIVER 21705 11095 16.5 5070 2.1 15.3 3970 1.9MACDONALD RIVER 21607.5 11192.5 16.4 5069 2.1 15.3 3969 1.9MACDONALD RIVER 21510 11290 16.4 5069 2.1 15.3 3969 2.0MACDONALD RIVER 21412.5 11387.5 16.4 5069 2.1 15.2 3969 2.0MACDONALD RIVER 21315 11485 16.3 5068 2.2 15.2 3969 2.0MACDONALD RIVER 21217.5 11582.5 16.3 5068 2.2 15.1 3968 2.0MACDONALD RIVER 21120 11680 16.2 5068 2.2 15.1 3968 2.1MACDONALD RIVER 21022.5 11777.5 16.2 5067 2.3 15.0 3968 2.1MACDONALD RIVER 20925 11875 16.1 5067 2.3 15.0 3968 2.1MACDONALD RIVER 20827.5 11972.5 16.0 5067 2.3 14.9 3968 2.1MACDONALD RIVER 20730 12070 16.0 5067 2.3 14.9 3967 2.2MACDONALD RIVER 20632.5 12167.5 15.9 5066 2.4 14.8 3967 2.2MACDONALD RIVER 20535 12265 15.9 5066 2.4 14.7 3967 2.2MACDONALD RIVER 20437.5 12362.5 15.8 5066 2.4 14.7 3967 2.2MACDONALD RIVER 20340 12460 15.8 5066 2.4 14.6 3967 2.2MACDONALD RIVER 20242.5 12557.5 15.7 5066 2.5 14.6 3967 2.3MACDONALD RIVER 20145 12655 15.6 5066 2.5 14.5 3967 2.3MACDONALD RIVER 20047.5 12752.5 15.6 5066 2.5 14.4 3967 2.3MACDONALD RIVER 19950 12850 15.5 5067 2.5 14.3 3968 2.4MACDONALD RIVER 19850.33 12949.67 15.4 5069 2.5 14.3 3969 2.3MACDONALD RIVER 19750.67 13049.33 15.4 5069 2.5 14.2 3969 2.3MACDONALD RIVER 19651 13149 15.3 5069 2.5 14.1 3969 2.3MACDONALD RIVER 19551.33 13248.67 15.2 5069 2.5 14.1 3968 2.3MACDONALD RIVER 19451.67 13348.33 15.2 5069 2.5 14.0 3968 2.3MACDONALD RIVER 19352 13448 15.1 5069 2.5 14.0 3968 2.3MACDONALD RIVER 19252.33 13547.67 15.1 5069 2.5 13.9 3968 2.3MACDONALD RIVER 19152.67 13647.33 15.0 5127 2.5 13.8 4013 2.3MACDONALD RIVER 19053 13747 14.9 5189 2.5 13.8 4060 2.3MACDONALD RIVER 18953.33 13846.67 14.9 5189 2.5 13.7 4059 2.3MACDONALD RIVER 18853.67 13946.33 14.8 5188 2.5 13.6 4059 2.3MACDONALD RIVER 18754 14046 14.8 5188 2.5 13.6 4059 2.3MACDONALD RIVER 18654.33 14145.67 14.7 5187 2.5 13.5 4058 2.3MACDONALD RIVER 18554.67 14245.33 14.6 5187 2.5 13.5 4058 2.3MACDONALD RIVER 18455 14345 14.6 5187 2.5 13.4 4058 2.3MACDONALD RIVER 18355.33 14444.67 14.5 5186 2.5 13.4 4057 2.3MACDONALD RIVER 18255.67 14544.33 14.5 5186 2.4 13.3 4057 2.2MACDONALD RIVER 18156 14644 14.4 5185 2.4 13.3 4057 2.2MACDONALD RIVER 18056.33 14743.67 14.4 5185 2.4 13.2 4056 2.2MACDONALD RIVER 17956.67 14843.33 14.3 5185 2.4 13.2 4056 2.2MACDONALD RIVER 17857 14943 14.3 5185 2.4 13.1 4056 2.2MACDONALD RIVER 17757.33 15042.67 14.2 5184 2.4 13.1 4056 2.2MACDONALD RIVER 17657.67 15142.33 14.2 5184 2.4 13.0 4056 2.2MACDONALD RIVER 17558 15242 14.1 5184 2.4 13.0 4056 2.1MACDONALD RIVER 17458.33 15341.67 14.1 5184 2.4 12.9 4055 2.1MACDONALD RIVER 17358.67 15441.33 14.0 5184 2.4 12.9 4055 2.1MACDONALD RIVER 17259 15541 14.0 5184 2.3 12.8 4055 2.1MACDONALD RIVER 17159.33 15640.67 13.9 5183 2.3 12.8 4055 2.1MACDONALD RIVER 17059.67 15740.33 13.9 5183 2.3 12.7 4054 2.1MACDONALD RIVER 16960 15840 13.8 5183 2.3 12.7 4054 2.1MACDONALD RIVER 16861.67 15938.33 13.8 5183 2.3 12.6 4054 2.0MACDONALD RIVER 16763.33 16036.67 13.7 5182 2.2 12.6 4054 2.0MACDONALD RIVER 16665 16135 13.7 5182 2.2 12.6 4053 2.0MACDONALD RIVER 16566.67 16233.33 13.7 5182 2.1 12.5 4053 1.9MACDONALD RIVER 16468.33 16331.67 13.6 5182 2.1 12.5 4053 1.9MACDONALD RIVER 16370 16430 13.6 5181 2.1 12.5 4053 1.9MACDONALD RIVER 16271.67 16528.33 13.6 5181 2.0 12.4 4052 1.8MACDONALD RIVER 16173.33 16626.67 13.5 5181 2.0 12.4 4052 1.8MACDONALD RIVER 16075 16725 13.5 5181 2.0 12.4 4052 1.8MACDONALD RIVER 15976.67 16823.33 13.5 5180 1.9 12.3 4052 1.7MACDONALD RIVER 15878.33 16921.67 13.4 5180 1.9 12.3 4051 1.7MACDONALD RIVER 15780 17020 13.4 5180 1.9 12.3 4051 1.7MACDONALD RIVER 15681.67 17118.33 13.4 5180 1.9 12.2 4051 1.7MACDONALD RIVER 15583.33 17216.67 13.3 5179 1.8 12.2 4050 1.6MACDONALD RIVER 15485 17315 13.3 5179 1.8 12.2 4050 1.6MACDONALD RIVER 15386.67 17413.33 13.3 5179 1.8 12.2 4050 1.6MACDONALD RIVER 15288.33 17511.67 13.3 5193 1.8 12.1 4060 1.6MACDONALD RIVER 15190 17610 13.2 5208 1.7 12.1 4071 1.6MACDONALD RIVER 15091.67 17708.33 13.2 5208 1.7 12.1 4071 1.5MACDONALD RIVER 14993.33 17806.67 13.2 5207 1.7 12.1 4070 1.5MACDONALD RIVER 14895 17905 13.2 5207 1.7 12.0 4070 1.5MACDONALD RIVER 14796.67 18003.33 13.1 5207 1.7 12.0 4069 1.5MACDONALD RIVER 14698.33 18101.67 13.1 5206 1.7 12.0 4069 1.5MACDONALD RIVER 14600 18200 13.1 5206 1.6 12.0 4069 1.5MACDONALD RIVER 14501.67 18298.33 13.1 5205 1.6 12.0 4069 1.4MACDONALD RIVER 14403.33 18396.67 13.0 5205 1.6 11.9 4068 1.4MACDONALD RIVER 14305 18495 13.0 5205 1.6 11.9 4068 1.4MACDONALD RIVER 14206.67 18593.33 13.0 5204 1.6 11.9 4068 1.4MACDONALD RIVER 14108.33 18691.67 13.0 5204 1.6 11.9 4068 1.4MACDONALD RIVER 14010 18790 12.9 5204 1.5 11.9 4068 1.4MACDONALD RIVER 13951.85 18848.15 12.9 5204 1.5 11.8 4068 1.4MACDONALD RIVER 13893.69 18906.31 12.9 5204 1.5 11.8 4067 1.3MACDONALD RIVER 13893.69 18906.31 12.9 5481 1.5 11.8 4279 1.3MACDONALD RIVER 13870 18930 12.9 5481 1.6 11.8 4279 1.4MACDONALD RIVER 13770.4 19029.6 12.9 5480 1.6 11.8 4279 1.4MACDONALD RIVER 13670.8 19129.2 12.9 5480 1.6 11.8 4278 1.4MACDONALD RIVER 13571.2 19228.8 12.8 5479 1.6 11.8 4278 1.4MACDONALD RIVER 13471.6 19328.4 12.8 5479 1.6 11.7 4277 1.4MACDONALD RIVER 13372 19428 12.8 5478 1.6 11.7 4277 1.4MACDONALD RIVER 13272.4 19527.6 12.8 5478 1.6 11.7 4276 1.4MACDONALD RIVER 13172.8 19627.2 12.7 5477 1.6 11.7 4276 1.4


MACDONALD RIVER 13073.2 19726.8 12.7 5477 1.6 11.6 4275 1.5MACDONALD RIVER 12973.6 19826.4 12.7 5476 1.6 11.6 4275 1.5MACDONALD RIVER 12874 19926 12.7 5476 1.6 11.6 4274 1.5MACDONALD RIVER 12774.4 20025.6 12.6 5475 1.6 11.6 4274 1.5MACDONALD RIVER 12674.8 20125.2 12.6 5475 1.6 11.5 4273 1.5MACDONALD RIVER 12575.2 20224.8 12.6 5474 1.6 11.5 4273 1.5MACDONALD RIVER 12475.6 20324.4 12.6 5474 1.7 11.5 4272 1.5MACDONALD RIVER 12376 20424 12.5 5473 1.7 11.5 4272 1.5MACDONALD RIVER 12276.4 20523.6 12.5 5473 1.7 11.4 4271 1.5MACDONALD RIVER 12176.8 20623.2 12.5 5472 1.7 11.4 4271 1.5MACDONALD RIVER 12077.2 20722.8 12.4 5472 1.7 11.4 4271 1.5MACDONALD RIVER 11977.6 20822.4 12.4 5471 1.7 11.3 4271 1.5MACDONALD RIVER 11878 20922 12.4 5470 1.7 11.3 4270 1.5MACDONALD RIVER 11778.4 21021.6 12.3 5470 1.7 11.3 4270 1.5MACDONALD RIVER 11678.8 21121.2 12.3 5469 1.7 11.2 4270 1.5MACDONALD RIVER 11579.2 21220.8 12.3 5469 1.7 11.2 4269 1.5MACDONALD RIVER 11479.6 21320.4 12.2 5469 1.7 11.2 4269 1.6MACDONALD RIVER 11380 21420 12.2 5469 1.7 11.2 4269 1.6MACDONALD RIVER 11280.71 21519.29 12.2 5468 1.7 11.1 4268 1.6MACDONALD RIVER 11181.43 21618.57 12.1 5468 1.8 11.1 4268 1.6MACDONALD RIVER 11082.14 21717.86 12.1 5468 1.8 11.0 4268 1.6MACDONALD RIVER 10982.86 21817.14 12.1 5468 1.8 11.0 4267 1.6MACDONALD RIVER 10883.57 21916.43 12.0 5467 1.8 11.0 4267 1.6MACDONALD RIVER 10784.29 22015.71 12.0 5467 1.8 10.9 4267 1.6MACDONALD RIVER 10685 22115 11.9 5467 1.8 10.9 4266 1.6MACDONALD RIVER 10585.71 22214.29 11.9 5467 1.8 10.9 4266 1.6MACDONALD RIVER 10486.43 22313.57 11.9 5466 1.9 10.8 4266 1.7MACDONALD RIVER 10387.14 22412.86 11.8 5466 1.9 10.8 4265 1.7MACDONALD RIVER 10287.86 22512.14 11.8 5466 1.9 10.8 4265 1.7MACDONALD RIVER 10188.57 22611.43 11.7 5465 1.9 10.7 4265 1.7MACDONALD RIVER 10089.29 22710.71 11.7 5465 1.9 10.7 4264 1.7MACDONALD RIVER 9990 22810 11.6 5465 1.9 10.6 4264 1.7MACDONALD RIVER 9891.11 22908.89 11.6 5465 1.9 10.6 4264 1.7MACDONALD RIVER 9792.22 23007.78 11.6 5464 1.9 10.6 4264 1.7MACDONALD RIVER 9693.33 23106.67 11.5 5464 1.9 10.5 4264 1.7MACDONALD RIVER 9594.45 23205.55 11.5 5464 1.9 10.5 4264 1.7MACDONALD RIVER 9495.55 23304.45 11.4 5464 1.9 10.4 4264 1.7MACDONALD RIVER 9396.67 23403.33 11.4 5463 1.9 10.4 4263 1.7MACDONALD RIVER 9297.78 23502.22 11.4 5463 1.9 10.4 4263 1.7MACDONALD RIVER 9198.89 23601.11 11.3 5463 1.9 10.3 4263 1.7MACDONALD RIVER 9100 23700 11.3 5462 1.9 10.3 4263 1.7MACDONALD RIVER 9001.11 23798.89 11.2 5462 1.9 10.2 4263 1.7MACDONALD RIVER 8902.22 23897.78 11.2 5462 1.9 10.2 4263 1.7MACDONALD RIVER 8803.33 23996.67 11.1 5461 1.9 10.2 4262 1.7MACDONALD RIVER 8704.45 24095.55 11.1 5461 1.9 10.1 4262 1.7MACDONALD RIVER 8605.55 24194.45 11.1 5461 1.9 10.1 4262 1.7MACDONALD RIVER 8506.67 24293.33 11.0 5485 1.9 10.0 4279 1.7MACDONALD RIVER 8407.78 24392.22 11.0 5509 1.9 10.0 4296 1.7MACDONALD RIVER 8308.89 24491.11 10.9 5509 1.9 9.9 4296 1.7MACDONALD RIVER 8210 24590 10.9 5508 1.9 9.9 4296 1.7MACDONALD RIVER 8114.09 24685.91 10.8 5508 1.9 9.8 4296 1.8MACDONALD RIVER 8018.18 24781.82 10.8 5507 1.9 9.8 4295 1.8MACDONALD RIVER 7922.27 24877.73 10.7 5507 2.0 9.7 4295 1.8MACDONALD RIVER 7826.36 24973.64 10.7 5507 2.0 9.7 4295 1.8MACDONALD RIVER 7730.46 25069.54 10.6 5507 2.0 9.6 4295 1.8MACDONALD RIVER 7634.54 25165.46 10.6 5507 2.0 9.6 4294 1.8MACDONALD RIVER 7538.64 25261.36 10.5 5506 2.0 9.5 4294 1.8MACDONALD RIVER 7442.73 25357.27 10.4 5506 2.0 9.5 4294 1.8MACDONALD RIVER 7346.82 25453.18 10.4 5506 2.0 9.4 4294 1.8MACDONALD RIVER 7250.91 25549.09 10.3 5506 2.0 9.4 4293 1.8MACDONALD RIVER 7155 25645 10.3 5506 2.1 9.3 4293 1.9MACDONALD RIVER 7059.09 25740.91 10.2 5506 2.1 9.3 4293 1.9MACDONALD RIVER 6963.18 25836.82 10.2 5505 2.1 9.2 4293 1.9MACDONALD RIVER 6867.27 25932.73 10.1 5505 2.1 9.2 4292 1.9MACDONALD RIVER 6771.36 26028.64 10.1 5505 2.1 9.1 4292 1.9MACDONALD RIVER 6675.46 26124.54 10.0 5505 2.1 9.1 4292 1.9MACDONALD RIVER 6579.54 26220.46 10.0 5505 2.1 9.0 4292 1.9MACDONALD RIVER 6483.64 26316.36 9.9 5505 2.1 9.0 4292 1.9MACDONALD RIVER 6387.73 26412.27 9.9 5504 2.2 8.9 4292 1.9MACDONALD RIVER 6291.82 26508.18 9.8 5504 2.2 8.9 4292 1.9MACDONALD RIVER 6195.91 26604.09 9.7 5504 2.2 8.8 4292 1.9MACDONALD RIVER 6100 26700 9.7 5504 2.2 8.8 4292 1.9MACDONALD RIVER 6004.37 26795.63 9.6 5504 2.2 8.7 4291 1.9MACDONALD RIVER 5908.75 26891.25 9.6 5504 2.2 8.7 4291 1.9MACDONALD RIVER 5813.12 26986.88 9.5 5503 2.2 8.6 4291 1.9MACDONALD RIVER 5717.5 27082.5 9.5 5503 2.1 8.6 4291 1.9MACDONALD RIVER 5621.87 27178.13 9.5 5503 2.1 8.6 4291 1.9MACDONALD RIVER 5526.25 27273.75 9.5 5503 2.1 8.5 4291 1.9MACDONALD RIVER 5430.62 27369.38 9.5 5503 2.1 8.5 4291 1.9MACDONALD RIVER 5335 27465 9.5 5502 2.1 8.4 4291 1.9MACDONALD RIVER 5239.37 27560.63 9.5 5502 2.1 8.4 4291 1.8MACDONALD RIVER 5143.75 27656.25 9.5 5502 2.1 8.3 4290 1.8MACDONALD RIVER 5048.12 27751.88 9.5 5502 2.1 8.3 4290 1.8MACDONALD RIVER 4952.5 27847.5 9.5 5501 2.1 8.2 4290 1.8MACDONALD RIVER 4856.87 27943.13 9.5 5501 2.0 8.2 4290 1.8MACDONALD RIVER 4761.25 28038.75 9.5 5501 2.0 8.1 4290 1.8MACDONALD RIVER 4665.62 28134.38 9.5 5501 2.0 8.1 4290 1.8MACDONALD RIVER 4570 28230 9.5 5500 2.0 8.0 4290 1.8MACDONALD RIVER 4470.55 28329.45 9.5 5500 2.0 8.0 4290 1.8MACDONALD RIVER 4371.11 28428.89 9.5 5500 2.1 8.0 4289 1.8MACDONALD RIVER 4271.67 28528.33 9.5 5500 2.1 8.0 4289 1.8MACDONALD RIVER 4172.22 28627.78 9.5 5500 2.1 8.0 4289 1.8MACDONALD RIVER 4072.78 28727.22 9.5 5500 2.1 8.0 4289 1.9MACDONALD RIVER 3973.33 28826.67 9.5 5500 2.1 8.0 4289 1.9MACDONALD RIVER 3873.89 28926.11 9.5 5500 2.2 8.0 4289 1.9MACDONALD RIVER 3774.45 29025.55 9.5 5500 2.2 8.0 4289 1.9MACDONALD RIVER 3675 29125 9.5 5500 2.2 8.0 4289 2.0MACDONALD RIVER 3579.32 29220.68 9.5 5500 2.2 8.0 4289 1.9MACDONALD RIVER 3483.64 29316.36 9.5 5500 2.2 8.0 4289 1.9MACDONALD RIVER 3387.96 29412.04 9.5 5500 2.2 8.0 4289 1.9MACDONALD RIVER 3292.27 29507.73 9.5 5500 2.1 8.0 4289 1.9MACDONALD RIVER 3196.59 29603.41 9.5 5499 2.1 8.0 4289 1.9MACDONALD RIVER 3100.91 29699.09 9.5 5499 2.1 8.0 4289 1.9MACDONALD RIVER 3005.23 29794.77 9.5 5499 2.1 8.0 4289 1.9


MACDONALD RIVER 2909.54 29890.46 9.5 5499 2.1 8.0 4289 1.8MACDONALD RIVER 2813.86 29986.14 9.5 5499 2.1 8.0 4289 1.8MACDONALD RIVER 2718.18 30081.82 9.5 5499 2.1 8.0 4289 1.8MACDONALD RIVER 2622.5 30177.5 9.5 5499 2.0 8.0 4289 1.8MACDONALD RIVER 2526.82 30273.18 9.5 5499 2.0 8.0 4289 1.8MACDONALD RIVER 2431.14 30368.86 9.5 5498 2.0 8.0 4289 1.8MACDONALD RIVER 2335.46 30464.54 9.5 5498 2.0 8.0 4289 1.8MACDONALD RIVER 2239.77 30560.23 9.5 5498 2.0 8.0 4289 1.8MACDONALD RIVER 2144.09 30655.91 9.5 5498 2.0 8.0 4289 1.8MACDONALD RIVER 2048.41 30751.59 9.5 5498 2.0 8.0 4289 1.7MACDONALD RIVER 1952.73 30847.27 9.5 5498 2.0 8.0 4289 1.7MACDONALD RIVER 1857.04 30942.96 9.5 5497 2.0 8.0 4289 1.7MACDONALD RIVER 1761.36 31038.64 9.5 5497 2.0 8.0 4289 1.7MACDONALD RIVER 1665.68 31134.32 9.5 5497 2.0 8.0 4289 1.7MACDONALD RIVER 1570 31230 9.5 5497 1.9 8.0 4289 1.7MACDONALD RIVER 1471.87 31328.13 9.5 5497 2.0 8.0 4289 1.7MACDONALD RIVER 1373.75 31426.25 9.5 5497 2.0 8.0 4289 1.8MACDONALD RIVER 1275.62 31524.38 9.5 5497 2.0 8.0 4289 1.8MACDONALD RIVER 1177.5 31622.5 9.5 5497 2.1 8.0 4289 1.8MACDONALD RIVER 1079.37 31720.63 9.5 5497 2.1 8.0 4289 1.8MACDONALD RIVER 981.25 31818.75 9.5 5497 2.2 8.0 4289 1.9MACDONALD RIVER 883.12 31916.88 9.5 5497 2.2 8.0 4289 1.9MACDONALD RIVER 785 32015 9.5 5497 2.3 8.0 4289 2.0MACDONALD RIVER 686.87 32113.13 9.5 5498 2.3 8.0 4289 2.0MACDONALD RIVER 588.75 32211.25 9.5 5498 2.4 8.0 4289 2.1MACDONALD RIVER 490.62 32309.38 9.5 5498 2.5 8.0 4289 2.1MACDONALD RIVER 392.5 32407.5 9.5 5498 2.6 8.0 4289 2.2MACDONALD RIVER 294.37 32505.63 9.5 5498 2.7 8.0 4290 2.3MACDONALD RIVER 196.25 32603.75 9.5 5498 2.9 8.0 4290 2.4MACDONALD RIVER 98.12 32701.88 9.5 5499 3.1 8.0 4290 2.5MACDONALD RIVER 0 32800 9.5 5499 3.5 8.0 4290 2.7

WRIGHTS CREEK 1410.78 0 12.9 566 0.3 11.8 465 0.3WRIGHTS CREEK 1313.86 96.92 12.9 557 0.3 11.8 460 0.3WRIGHTS CREEK 1216.93 193.85 12.9 547 0.3 11.8 455 0.3WRIGHTS CREEK 1120.01 290.77 12.9 538 0.3 11.8 450 0.3WRIGHTS CREEK 1023.09 387.69 12.9 529 0.3 11.8 444 0.3WRIGHTS CREEK 926.16 484.62 12.9 520 0.3 11.8 440 0.3WRIGHTS CREEK 829.24 581.54 12.9 511 0.3 11.8 435 0.3WRIGHTS CREEK 732.32 678.46 12.9 503 0.3 11.8 430 0.3WRIGHTS CREEK 635.4 775.38 12.9 494 0.3 11.8 425 0.3WRIGHTS CREEK 538.47 872.31 12.9 486 0.3 11.8 421 0.3WRIGHTS CREEK 441.55 969.23 12.9 478 0.3 11.8 416 0.3WRIGHTS CREEK 344.63 1066.15 12.9 470 0.3 11.8 412 0.3WRIGHTS CREEK 247.7 1163.08 12.9 463 0.3 11.8 408 0.3WRIGHTS CREEK 150.78 1260 12.9 455 0.3 11.8 404 0.3WRIGHTS CREEK 75.39 1335.39 12.9 449 0.3 11.8 401 0.3WRIGHTS CREEK 0 1410.78 12.9 444 0.3 11.8 397 0.3


River name Chainage from MIKE11 5 Year ARI Extreme EventHawkesbury River (m) Chainage (m) Flood Peak






lower macdonald river flood study...lower macdonald river flood study webb, mckeown & associates...

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