site specific flood risk assessment new student ... · site specific flood risk assessment ref: 26...

$: SITE SPECIFIC FLOOD RISK ASSESSMENT NEW STUDENT ... · Site Specific Flood Risk Assessment REF: 26 098 / F5.1 PROJECT: NEW STUDENT ACCOMMODATION DATE: 3RD JANUARY 2018 R:\Docs\PROJECTS\26$
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Revision B

SITE SPECIFIC FLOOD RISK ASSESSMENT

NEW STUDENT ACCOMMODATION, FASSAUGH AVENUE, CABRA, DUBLIN 7

26 098 / F5.1

3RD

JANUARY 2018

Site Specific Flood Risk Assessment

REF: 26 098 / F5.1

PROJECT: NEW STUDENT ACCOMMODATION DATE: 3RD JANUARY 2018

R:\Docs\PROJECTS\26 000\26 098\F5.1\18.01.03 Final Planning Pack\Flood Risk Assessment\Site Specific Flood Risk Assessment EB AK 17.08.24.docx

72 Haddington Road, Ballsbridge, Dublin 4, D04 E097 T: +353 (0)1 660 9000 E: [email protected] W: www.mea.ie

2

1 INTRODUCTION

1.1 It is intended to apply for Planning Permission to construct student

accommodation on a circa 0.4959 ha site located on Fassaugh Avenue,

Dublin 7. The proposed development will also include construction for

an internal vehicle access road and some car parking.

1.2 This document should be read in conjunction with the following

drawings:

26 098/CD/003 EXISTING SITE PLAN

26 098/CD/004 PROPOSED SITE DRAINAGE LAYOUT PLAN

26 098/CD/005 PROPOSED SITE DRAINAGE LONGITUDINAL

SECTIONS

26 098/CD/006 DRAINAGE DETAILS SHEET 1

26 098/CD/007 DRAINAGE DETAILS SHEET 2

26098/CD/010 DETAILS OF PROPOSED DRAINAGE OUTFALLS TO

SEWERS

1.3 The flood Risk Assessment for this site has been carried out in

accordance with the process set out in ‘The Planning System and Flood

Risk Management Guidelines for Planning Authorities’ published by the

Office of Public Works

2 DESCRIPTION OF THE EXISTING SITE

2.1 The site is bounded by Fassaugh Avenue to the south, the railway cutting

to the west and residential housing to the east and north.

2.2 Access to the site is from Fassaugh Avenue

2.3 There is an existing derelict public house and associated structures with a

paved carpark located at the southern Fassaugh Avenue end of the site.

The carpark is level with the public road. The building and carpark

occupy approximately 25% of the site area. The rest of the site consists

of undeveloped greenfield land.


REF: 26 098 / F5.1




3

2.4 Immediately north of the derelict public house the existing ground

profile rises steeply to approximately 3.5m above the road level. The

existing site elevation is highest at the north end of the site. It is

understood that the current ground profile resulted from excavated

material from the railway construction being stockpiled on the site.

3 DESCRIPTION OF THE PROPOSED DEVELOPMENT

3.1 It is proposed to demolish the derelict public house and associated

structures at the south end of the site.

3.2 The existing excavated material stockpiled on the site during the

construction of the railway will be excavated and removed. This will

facilitate access from Fassaugh Avenue to all parts of the site including

the new buildings.

3.3 The proposed student accommodation is divided into three multi-storey

blocks. The largest blocks, A and B, will be located near the west

boundary of the site. Blocks A and B will be designed as cellular

structures with internal load bearing walls. Block C will be designed as a

framed structure with concrete shear walls.

The buildings will be supported on bored pile foundations.

A common single level basement will be provided under Blocks A and B.

3.4 Access into the development will be via a new paved road from Fassaugh

Avenue.

4 HISTORICAL FLOODING

4.1 The Office of Public Works website ‘floodmaps.ie’ provides information

on historical flooding. The Map Report reproduced in Appendix 1 is taken

from this website and shows all flood events within 2.5km of the site. It

is noted that there is no record of flooding on or adjacent to the site.

5 DEVELOPMENT VULNERABILITY CLASS

5.1 The proposed development involves construction of student halls of

residence. As such the appropriate development vulnerability class is

“highly vulnerable development” in accordance of table 3.1 of the

guidelines


REF: 26 098 / F5.1




4

6 PLUVIAL FLOODING

6.1 The flood risk map for Dublin City (map 2019 / Map / 238A), reproduced

in Appendix 2 is taken from The Draft Preliminary Flood Risk Assessment

(August 2011) published by the Office of Public Works. This map

indicates that the site is not at risk from pluvial flooding.

6.2 The Office of Public Works flood mapping data is also available on the

‘MyPlan.ie’ website managed by the Department of Environment,

Community and Local Government. An extract from this website is

presented in Appendix 3. This map also indicates that the site is not at

risk from pluvial flooding.

6.3 A pluvial flood map for the site is contained in Appendix 4. This is an

extract from the “Flood ResilienCity Final Report Volume 2, Appendix B”

produced for Dublin City Council by Jacobs Consulting. This map

indicates that the railway cutting west of the site is at risk from pluvial

flooding. It is noted that the site of the proposed development is

substantially higher than the existing railway cutting.

6.4 The proposed development will maintain the existing direction of

overland flow towards the south of the site and away from the proposed

buildings. Furthermore it is noted that the proposed stormwater

attenuation system is designed for a 1% AEP flood event allowing for

20% increase due to climate change. The site is at minimal risk from

Pluvial Flooding.

7 FLUVIAL FLOODING

7.1 The flood risk map for Dublin City (map 2019 / Map / 238A) reproduced

in Appendix 2, is taken from ‘The Draft Preliminary Floor Risk

Assessment’ (August 2011) published by the Office of Public Works. This

map indicates that the site is not at risk from fluvial flooding.

7.2 The River Tolka is approximately 1.2km north of the site and the River

Liffey is approximately 2.0km to the south. Therefore, the site is not at

risk from fluvial flooding from these rivers.

7.3 In the case of fluvial flooding the site location meets the criteria for Flood

Zone C as set out in Clause 2.23 of the Guidelines. As such, it is

concluded that there is no risk of fluvial damage.


REF: 26 098 / F5.1




5

8 ROYAL CANAL

8.1 The Royal Canal is located approximately 250mm north of the site. If the

canal was to overflow the resulting flood water would flow into the

railway cutting and away from the proposed development.

9 TIDAL FLOODING

9.1 The Tidal Flood Extent Map for Dublin City (map NE / RA / EXT / HEFS /

19 / 0) reproduced in Appendix 5, is taken from ‘The Irish Coastal

Protection Strategy Study – Phase III’ (August 2013). This map shows the

tidal flood zone for the 10% AEP, 0.5% AEP and 0.1% AEP events.

9.2 It is stated on map NE / RA / EXT / HEFS / 19 / 0 that the estimated flood

levels would be 3.67m AOD, 4.07m AOD and 4.28 AOD for the 10%, 0.5%

and 0.1% AEP events respectively. The lowest proposed ground floor

level for the new buildings will be 34.000m AOD.

9.3 In the case of tidal flooding the site location meets the criteria for Flood

Zone C as set out in the Clause 2.23 of the Guidelines. As such it is

concluded that there is no risk of tidal flooding.

10 GROUND WATER FLOODING

10.1 The flood risk map for Dublin City (map 2019 / Map / 238A), reproduced

in Appendix 1 is taken from The Draft Preliminary Flood Risk Assessment

(August 2011) published by the Office of Public Works. This map

indicates that the site is not at risk from flooding due to ground water.

10.2 It is noted that there is no record of flooding on this site due to ground

water.

10.3 It is considered extremely unlikely that ground water levels on site will

rise above ground level. However if this was to occur the water would

follow the overland flood routes and away from the buildings.

11 PROPOSED DRAINAGE AND WATER SUPPLY SYSTEMS

11.1 The surface water drainage from the building roofs and paved areas will

collect in a below ground drainage network of 225mm diameter pipes

which will drain by gravity to the surface water pumping station near the

southern site boundary.


REF: 26 098 / F5.1




6

11.2 A flow control device in conjunction with an attenuation tank will limit

the maximum rate of discharge of surface water from the site to 2l/s as

agreed with Dublin City Council Drainage Department.

11.3 The pumping station will incorporate a pump with sufficient capacity to

convey the design flow. A second pump will also be provided as back-up.

The two pumps will operate in duty-standby rotation. The attenuation

tank will insure that the surface water drainage system can provide 24-

hour emergency storage in the unlikely event of failure of both pumps.

11.4 The proposed site drainage system is designed to achieve self-cleaning

velocity. This will prevent the build-up of silt deposits in the system

which could cause blockage and possibly result in flooding.

11.5 All elements of the proposed site drainage systems (pipelines and

manholes) will be tested to ensure that they are watertight.

11.6 Water supply mains will be pressure tested to ensure that they can

perform satisfactorily without bursting or leakage.

11.7 With the incorporation of the mitigation measures described above the

risk of flooding associated with the proposed drainage and water supply

systems is negligible.


REF: 26 098 / F5.1




7

APPENDIX 1: MAP REPORT FROM OPW WEBSITE FLOODMAPS.ie

Summary Local Area Report

Map Scale

This Flood Report has been downloaded from the Web site www.floodmaps.ie. The users should take account of the restrictions and limitations relating to the content and use of this Web site that are explained in the Disclaimer box when entering the site. It is a condition of use of the Web site that you accept the User Declaration and the Disclaimer.

25 Results

This Flood Report summarises all flood events within 2.5 kilometres of the map centre.

Map Legend

Flood Points

Multiple / Recurring Flood Points

Areas Flooded

Hydrometric Stations

Rivers

Lakes

River Catchment Areas

1:8,183

Land Commission *

Drainage Districts *

Benefiting Lands *

* Important: These maps do not indicate flood hazard or flood extent. Thier purpose and scope is explained in the Glossary.

Dublin

O 139 364

The map centre is in:

County:

NGR:

1. Flooding at Glendhu Park, Cabra, Dublin 7 on 24th Oct 2011 24/Oct/2011Start Date:

County: Flood Quality Code:

Additional Information: Reports (1) More Mapped Information

Dublin 3

2. Tolka December 1954 08/Dec/1954Start Date:


Additional Information: Photos (2) Reports (13) Press Archive (9) More Mapped Information

Dublin 1

3. Tolka November 2002 13/Nov/2002Start Date:


Additional Information: Photos (126) Reports (9) Videos (3) Press Archive (13) More Mapped Information

Meath, Dublin 1

4. Dublin City Tidal Feb 2002 01/Feb/2002Start Date:


Additional Information: Photos (32) Reports (10) Press Archive (27) More Mapped Information

Dublin 1

5. Tolka River 24th Oct 2011 Botanic Gardens 24/Oct/2011Start Date:

County: Flood Quality Code:Dublin 2

Report Produced: 11-Jul-2017 14:53


REF: 26 098 / F5.1


R:\Docs\PROJECTS\26 000\26 098\F5.1\18.01.03 Final Planning Pack\Flood Risk Assessment\Site Specific Floor Risk Assessment EB AK 17.08.24.docx


8

APPENDIX 2: FLOOD RISK MAP FOR DUBLIN CITY (MAP 2019 / MAP / 238A)

kj

kj

kj

kj

¯

Legend:

Location Plan :

Flood Extents

PFRA Outcomes

kj

kj


REF: 26 098 / F5.1




9

APPENDIX 3: AN EXTRACT FROM THE OFFICE OF PUBLIC WORKS FLOOD MAPPING DATA FROM

THE ‘MYPLAN.IE’ WEBSITE


REF: 26 098 / F5.1




1

0

An extract from the Office of Public Works flood mapping data from the‘MyPlan.ie’ website managed

by the Department of Environment, Community and Local Government.

SITE

LOCATION


REF: 26 098 / F5.1




1

1

APPENDIX 4: PLUVIAL FLOOD MAP EXTRACT FROM THE “FLOOD RESILIENCITY FINAL REPORT

VOLUME 2, APPENDIX B” PRODUCED FOR DUBLIN CITY COUNCIL BY JACOBS

CONSULTING.

309500 310000 310500 311000 311500 312000 312500 313000 313500 314000 314500 315000 315500 316000 316500 317000

235000

235500

236000

236500

237000

237500

238000

238500

239000

239500

240000

240500

241000

Revision

FINAL v1

NTSDrawn

3. Dublin Central

2. Dublin North Central

5. Dublin South Central

4. Dublin South East

1. Dublin North West

Client

Project

Title

Drawing Status

Job No.

Figure No.

Scale

Copyright reserved

Jacobs UK Ltd

28 Adelaide Street,Rochester Building, Belfast, BT2 8GD

0 0.9 1.80.45

Km

±Ponding Areas

Dublin North West/Central

Ponding Areas

Copyright © Ordinance Survey Ireland. Licence number 2010/22/CCMA/ Dublin City Council.

Checked ApprovedReview

Nov 29, 2010

32102500

Dublin Flood Resilien City Project

32102500/001

Type 1 Model

LM RFPS JC

Dublin City Council Administrative Boundaries

Sheet 1 of 5

Sheet 1 of 5

Note:

Please refer to report for information on Type 1 model limitations


REF: 26 098 / F5.1




1

2

APPENDIX 5: TIDAL FLOOD EXTENT MAP FOR DUBLIN CITY (MAP NE / RA / EX / 19 / 1) TAKEN

FROM ‘THE DRAFT PRELIMINARY FLOOD RISK ASSESSMENT’ (AUGUST 2011).

!

Point 22

0.5 0 0.5 1 1.5 20.25

Kilometers

±

© Government of Ireland

Osi permit number EN-002-1012

(1 in 200 chance in any given year)

Elmwood House74 Boucher Road

BelfastBT 12 6RZ

Northern Ireland

Office of Public Works17-19 Lower Hatch Street

Dublin 2Ireland

High Water Mark (HWM)

Node Point

0.5% AEP FLOOD EXTENT

USER NOTE :

USERS OF THESE MAPS SHOULD REFER TO THE DETAILED

DESCRIPTION OF THEIR DERIVATION, LIMITATIONS INACCURACY AND GUIDANCE AND CONDITIONS OF USE

PROVIDED AT THE FRONT OF THIS BOUND VOLUME. IF THIS

MAP DOES NOT FORM PART OF A BOUND VOLUME, IT

SHOULD NOT BE USED FOR ANY PURPOSE.

1:25,000

JMC & JR

Figure By :

Checked By :

Plot Scale : 1:1 @ A3Drawing Scale :

Figure No. :

PJW

Project :

IRISH COASTAL PROTECTION STRATEGYSTUDY - PHASE III

Map :

NORTH EAST COAST FLOOD EXTENT MAP

TIDAL FLOODING

Map Type :

Source :

Map area :

FLOOD EXTENT

RURAL AREA

HIGH END FUTURE SCENARIOScenario :

Node Label (refer to table)Point 34

Legend:

EXTENT MAP

Location Plan :

Date :

Date : Sept 2012

Sept 2012

Revision

NE / RA / EXT / HEFS / 19

(1 in 1000 chance in any given year)

0.1% AEP FLOOD EXTENT

0

Water Level (mOD Malin) per AEP

Node Label WL 10% WL 0.5% WL 0.1%

Point 22 3.67 4.07 4.28

NOTE: MORE DETAILED MAPS SHOWING COMBINED TIDAL AND FLUVIAL FLOOD

HAZARD FOR PART OF THIS AREA (DODDER CATCHMENT ONLY)

HAVE BEEN PREPARED UNDER THE RIVER DODDER CATCHMENT

FRAM STUDY. PLEASE REFER TO WWW.DUBLINCITY.IE/PAGES/DODDERFLOODINGSTUDY.ASPX

FOR MORE INFORMATION

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