44.3 summary of rapid reach assessment .3 summary of rapid

HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 103

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4.3 Summary of rapid reach assessment 4.3 Summary of rapid reach assessment results - values and threats results - values and threats

The rapid reach assessment for the Strategy assessed environmental, social and economic values and

threats for river reaches in the Hawkesbury Nepean catchment. A number of these form the basis of

eight Management Themes (see Volume 1, section 2.3). The remaining values and threats inform the

detailed management actions in Appendix 4.2 and are summarised and mapped in this section.

Environmental Values

Riparian Vegetation

Riparian land with intact vegetation is critically important to the health of a waterway because it

provides:

• Organic matter to the river, a major food source for aquatic fauna

• A supply of woody debris within the river, which forms key habitat areas for many fi sh and

invertebrates

• A source of shade in upland areas which infl uences water temperature and light penetration

producing suitable conditions for aquatic fl ora and fauna

• Assistance in bank stabilization, reducing erosion in many areas.

Vegetated riparian land also acts as a buff er between the catchment and river so it can fi lter nutrients

and sediment from catchment run-off and reduce the impacts of land use on the river itself.

The Rapid Reach Assessment Panels determined the percentage cover class of riparian vegetation

cover through aerial photograph interpretation and through local knowledge of the river reach.

The panel determined that 79 (53%) of the assessed river reaches have >50% riparian vegetation cover, while 49 (33%) have <25% riparian vegetation cover.

River Condition

The condition of river reaches in the Hawkesbury Nepean has been assessed by the Geomorphic

Categorisation of Streams in the Hawkesbury Nepean (DLWC, 2001a). The assessment of river condition

incorporated available data on historical changes, fl oodplain linkages, sediment mobility, human disturbance and changes to river character (DLWC, 2001a). Based on these assessments river reaches

were classifi ed into one of four condition categories.

In the Hawkesbury Nepean 31% of reaches are rated as having near intact condition, 28% as having good condition, 22% moderate and 19% degraded. Most of the catchment (59%) is in Near Intact or

Good condition as the topography and geology of much of the catchment has limited the extent of

land use change and vegetation removal in these areas (DLWC, 2001a).

104 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY104 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY104

Recovery potential

The concept of recovery potential refers to the ability of a river reach to respond to disturbance or to

“bounce back” following disturbance. Reaches with a high recovery potential are generally those that

have minimal impact from human modifi cations and do not require intervention for rehabilitation

(DLWC, 2001a). River reaches with low recovery potential are generally characterised by extensively

altered geomorphic conditions and poor vegetation associations. Impacts of reservoirs and weirs can

also limit the recovery potential (DLWC, 2001a). These reaches are also often degraded as a result of

poor upstream condition.

The recovery potential of streams in the Hawkesbury Nepean catchment has been determined by the

Geomorphic Categorisation of Streams in the Hawkesbury Nepean.

31% of the river reaches assessed have a very high recovery potential. This large percentage is due

to the fact that over half of the catchment is bushland, much of this in deep sandstone gorges with

minimal threats. A further 14% has a high recovery potential, 27% has a moderate recovery potential

and 28% has a low recovery potential (DLWC, 2001a).

Sites of environmental signifi cance

This is a registered conservation asset and refers to the listing of specifi c sites on either the Register

of the National Estate, as National Parks, or as part of the Greater Blue Mountains World Heritage Area.

These sites do not necessarily refl ect ecological value however they indicate a recognised importance

and have high levels of environmental protection.

Signifi cant vegetation community

The catchment contains many rare, threatened and endangered vegetation communities. Many of

these communities are under threat from pressures such as clearing, urban development and weeds,

and many of them occur in riparian corridors.

The location and extent of vegetation community types in the Hawkesbury Nepean catchment

is covered by the Priority 5 Mapping Area (P5MA) vegetation mapping undertaken by the NSW

Department of Environment and Conservation and Department of Natural Resources (DEC and DIPNR

(2005) Native Vegetation Mapping Report Series 5).

Endangered Ecological Communities (EECs) listed under State legislation (Threatened Species

Conservation Act) and Commonwealth legislation (Environmental Protection and Biodiversity Conservation Act) within 30m of a watercourse have been identifi ed and extracted from the P5MA

information and mapped. River reaches were assessed in terms of the presence or absence of these

EECs.


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Social Values

Swimming

The degree to which a river reach is used for swimming can be infl uenced by a number of factors.

These may include the suitability of the waterway in terms of depth etc, level of accessibility, and

how clean the water is. Swimming is an important recreational asset and one that also requires the

maintenance of these set of conditions.

The Rapid Reach Assessment Panel used local knowledge to rate the frequency of swimming at each of

the river reaches.

57 (38%) of the river reaches assessed are used for swimming.

Recreational Fishing

The Rapid Reach Assessment Panel used local knowledge to rate the frequency of recreational fi shing

at each of the river reaches. The occurrence of recreational fi shing is not only an indicator of the

important social value of a river reach but can also provide an indication of the health of the aquatic

populations in that reach.

The highest levels of recreational fi shing occur generally in the lower reaches of the catchment,

focusing on the estuary and also the freshwater tributaries that support the native Australian Bass.

Popular recreational fi shing locations in the upper reaches of the catchment are associated with exotic

fi sh species such as Trout.

67 of the assessed river reaches (45%) were identifi ed as being used for recreational fi shing.

Boating

Two types of boating were investigated as social assets to a river reach, both motor boating and

non-motor boating. Non-motor boating included canoeing and li-loing. Motor boat use was

restricted largely to the estuary of the Hawkesbury Nepean and the wider rivers in the lower part of

the catchment. Non-motor boating however was widespread across the catchment. There was a relationship between public river recreation access points and the occurrence of other social value

activities such as boating.

46 (31%) of the assessed reaches are used for non-motor boating and 18 (12%) of the assessed reaches

are used for motor boating.

Scenic QualityThe perception of the scenic quality of a river reach and its landscape may diff er from one person

to another, however where there was a general consensus among Rapid Reach Assessment Panel

members of the level of scenic quality of an area it was recorded. Sydney Regional Environment Plan 20 (Hawkesbury Nepean River) covers the lower section of the catchment and identifi es areas of scenic

quality of regional signifi cance. Reaches in National Park or World Heritage Area were considered to be

of State Signifi cance in terms of scenic quality.


Economic Values

Irrigation

Water extraction from rivers ranges from basic riparian rights, which allow users to extract water for

stock and domestic gardens, to high use water extraction for broad scale irrigation or industry. The

Rapid Assessment Panel assessed irrigation water supply as an economic asset.

The river reaches of highest water extraction for broad scale irrigation or industry include the

Hawkesbury Nepean River, South Creek and the lower Wollondilly River.

Commercial Fishing

The Hawkesbury Nepean River supports the second largest commercial coastal fi shery of prawns,

oysters and fi sh in NSW with a wholesale value of $6.3 million annually. Commercial fi shing industries in

the Hawkesbury Nepean are restricted to the estuary, with a trout farm on the Marangaroo River in the

Upper Coxs Subcatchment being the only exception.

Tourism

Rivers often provide a draw card for tourists due to their range of recreational and aesthetic values. The

Rapid Reach Assessment Panels were asked to assess the level of usage of river reaches by tourists. The

major focus area of tourists in the catchment is the Hawkesbury Nepean estuary.

Land use

The Rapid Reach Assessment Panel determined the class of land use dominating beside each river

reach. Land use type is typically closely linked to land use value. High productivity areas such as

intensive irrigation areas or urban residential areas are generally of higher economic value than grazing

land or bushland.

The Hawkesbury Nepean River fl oodplains contain the most intensive irrigation areas in the catchment

and the South Creek subcatchment is dominated by urban development land use.


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Threats

Damaging access

Riparian zones are sensitive areas of the landscape, easily susceptible to damage such as riverbank

erosion, native vegetation degradation and weed invasion. Unrestricted access from cattle or humans

down river and creek banks can cause serious erosion and grazing can degrade native vegetation.

The Rapid Reach Assessment Panels used a combination of aerial photographs and local knowledge

of the reaches to rate the degree of damage to riverbanks as a result of unmanaged stock or human

access.

The Panels found that 35 (25%) of assessed river reaches had observable stock or human access

damage to more than 10% of the reach. A further 46 (31%) had focused human access damage.

Woody weeds

The Rapid Reach Assessment Panels used a combination of aerial photograph interpretation and local

knowledge of river reaches to determine a percentage class of woody weed invasion. The highest

levels of woody weed invasion were in the Nepean River near Camden, the Hawkesbury River between

Yarramundi and Lower Portland, Cattai Creek and South Creek.

20 (13%) of the assessed river reaches have woody weeds making up >50% of their vegetation cover.

The majority of the river reaches in the catchment have little or no woody weed invasion.

Some of the more common woody weeds across the catchment include Honey Locust (Gleditsia

triacanthos), Privet, African Olive, and various species of Willow.

Pest animals

Some species of pest animals have the ability to create visible physical damage to riparian zones if

present in large enough numbers. The rapid reach assessment panels identifi ed problem pest animals

on the river reaches and indicated the level of damage they were causing.

26 of the river reaches assessed recorded some level of damage from pest animals.

Some of the common pest animals noted included pigs, deer, goats, rabbits, and feral cattle.

Flow regulation

The catchment contains a large number of dams and weirs scattered throughout the river system. These structures alter natural fl ow regimes and interrupt sediment transport, having serious impacts on

downstream environments.

40 of the river reaches assessed are dammed for water supply and thus regulated. This equates to

883km of waterway.

Extraction

The Stressed River Assessment Report for the Hawkesbury Nepean Catchment was used to determine the

level of Hydrologic Stress for each of the subcatchments. Most of the subcatchments outside reserved

lands experience a high level of hydrologic stress, largely infl uenced by high levels of extraction.


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Riparian VegetationRiparian Vegetation

Environmental AssetsEnvironmental Assets

Fig. A2


River ConditionRiver ConditionAdapted from DLWC(2001a) Adapted from DLWC(2001a)

“Geographic Categorisation of streams in the“Geographic Categorisation of streams in the

Hawkesbury Nepean catchment”Hawkesbury Nepean catchment”


Fig. A3


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GeomorphicGeomorphicRecovery PotentialRecovery Potential

Adapted from DLWC(2001a)Adapted from DLWC(2001a)

“Geographic Categorisation of streams in the“Geographic Categorisation of streams in the

Hawkesbury Nepean catchment”Hawkesbury Nepean catchment”

Fig. A4


Sites of EnvironmentalSites of EnvironmentalSignifi canceSignifi canceFig. A5



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Fig. A6


Signifi cant Vegetation Signifi cant Vegetation CommunityCommunity

AAdapted from P5MA mapping; Tindall, D. et. al. (2005) AAdapted from P5MA mapping; Tindall, D. et. al. (2005)

Native Vegetation Map Report Series. No. 4. Version 2.2. Native Vegetation Map Report Series. No. 4. Version 2.2.


Social AssetsSocial Assets

Fig. A7 SwimmingSwimming


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Fig. A8RecreationalRecreational

FishingFishing


Fig. A9


Non-MotorNon-MotorBoatingBoating


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Fig. A10


Motor Boating / Motor Boating / SkiingSkiing


Fig. A11


Scenic QualityScenic Quality


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Fig. A12

Economic AssetsEconomic Assets

Irrigation Water SupplyIrrigation Water Supply


Fig. A13


Commercial FishingCommercial Fishing


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Fig. A14


TourismTourism


Fig. A15


LanduseLanduse


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Fig. A16

ThreatsThreats

Damaging Access toDamaging Access toRiparian ZoneRiparian Zone


Exotic Plant SpeciesExotic Plant SpeciesRiparian Woody WeedsRiparian Woody WeedsFig. A17

ThreatsThreats


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Fig. A18

ThreatsThreats

Pest AnimalsPest Animals


Fig. A19

ThreatsThreats

Flow RegulationFlow Regulation


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Flow Modifi cation / Flow Modifi cation / Extraction

Adapted from Stressed Rivers Reporton the Hawkesbury Nepean

Fig. A20

ThreatsThreats

44.3 summary of rapid reach assessment .3 summary of rapid

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