MCR Properties Chesser House Car Park, Gorgie Road, Edinburgh Flood Risk Assessment Final September 2019 Kaya Consulting Limited 111 George Street, 2nd Floor, Edinburgh EH2 4JN, UK Tel: 01314661458, Web: www.kayaconsulting.co.uk Copyright of this Report is vested in Kaya Consulting Limited and no part of it may be copied or reproduced by any means without prior written permission from Kaya Consulting Limited. If you have received this Report in error, please destroy all copies in your possession and control and notify Kaya Consulting Limited. The findings and recommendations of this Report are for the use of the Client named on the cover and relate to the project described in the Report. Unless otherwise agreed in writing by Kaya Consulting Limited, no other party may use, make use of or rely on the contents of the report. No liability is accepted by Kaya Consulting Limited for any use of this report, other than for the purposes for which it was originally prepared and provided. Opinions and information provided in the report are on the basis of Kaya Consulting Limited using due skill, care and diligence in the preparation of the same. No independent verification of any of the documents or information supplied to Kaya Consulting Limited has been made. Kaya Consulting Limited 111 George Street, 2nd Floor, Edinburgh EH2 4JN, UK Tel: 01314661458, Web: www.kayaconsulting.co.uk Document Information and History Project: Chesser House Car Park, Gorgie Road, Edinburgh FRA Client: MCR Properties. Client Representative: Gregor King Kaya Consulting Job Number: KC1712 Filename: 1712-Chesser House Car Park, FRA SEP 19 Project Director: C Anderson Author P Fernandez This document has been issued and amended as follows: Version Date Description Created by: Verified by: Approved by: 1.0 06.09.2019 Draft P Fernandez C Anderson C Anderson 1.1 19.09.2019 Final P Fernandez C Anderson C Anderson 1.2 29.10.209 Final update P Fernandez C Anderson C Anderson Kaya Consulting Limited 111 George Street, 2nd Floor, Edinburgh EH2 4JN, UK Tel: 01314661458, Web: www.kayaconsulting.co.uk Kaya Consulting Ltd Table of Contents SEPA Checklist ................................................................................................................................ vi 1 Introduction ..................................................................................................................................... 1 2 Legislative and Policy Aspects ..................................................................................................... 3 2.1 National Planning Policy ............................................................................................................ 3 2.6 Controlled Activities Regulations (CAR) .................................................................................. 10 2.7 Climate Change ....................................................................................................................... 10 3 Site Location and Description ..................................................................................................... 11 4 Hydrological Analysis .................................................................................................................. 16 4.1 Catchment description ............................................................................................................. 16 4.2 Estimation of design flows using statistical methods .............................................................. 17 4.3 Estimation of design flows using runoff methods (with no reservoir attenuation) ................... 18 4.4 Selection of design flow estimates .......................................................................................... 19 5 Hydraulic Modelling ...................................................................................................................... 20 5.1 1D Model Set up ...................................................................................................................... 20 5.2 Model Calibration ..................................................................................................................... 22 5.3 Model Results .......................................................................................................................... 23 5.4 Sensitivity Analysis .................................................................................................................. 25 6 Flood Risk Assessment ............................................................................................................... 27 6.1 Flood Risk from Water of Leith ................................................................................................ 27 6.1.1 Existing Scenario .............................................................................................................. 27 6.1.2 Flood Management and Finished Floor Levels ................................................................ 27 6.2 Flooding Risk from Surface Water Runoff ............................................................................... 28 6.3 Groundwater ............................................................................................................................ 29 6.4 Site Drainage and Scottish Water System .............................................................................. 29 6.5 Flood Risk to Site Access ........................................................................................................ 30 7 Summary, Conclusions and Recommendations ....................................................................... 31 Appendix – Model cross sections – 200 yr ....................................................................................... 32 List of Figures Figure 1: General site location ................................................................................................................. 2 Figure 2: Detailed Site Location ............................................................................................................. 12 Figure 3: Site topographical levels (m AOD) ......................................................................................... 13 Figure 4: Catchment area draining to site .............................................................................................. 16 Figure 5: Cross section location map .................................................................................................... 21 Figure 6: Modelled 2D domain (denoted in purple) ............................................................................... 22 Figure 7: 200 year flood extent .............................................................................................................. 23 Figure 8: Indicative overland flow paths ................................................................................................ 29 List of Photographs Photo 1: View of the site looking north-east. ......................................................................................... 14 1712-Chesser House Car Park, FRA SEP 19 V1.2 iv Kaya Consulting Ltd Photo 2: Water of Leith looking downstream from Gorgie Road bridge ................................................ 14 Photo 3: Foot bridge downstream of the site ......................................................................................... 15 Photo 4: Gorgie Road bridge upstream of site ...................................................................................... 15 1712-Chesser House Car Park, FRA SEP 19 V1.2 v Kaya Consulting Ltd SEPA Checklist 1712-Chesser House Car Park, FRA SEP 19 V1.2 vi Kaya Consulting Ltd 1712-Chesser House Car Park, FRA SEP 19 V1.2 vii Kaya Consulting Ltd 1 Introduction Kaya Consulting Ltd. was commissioned by MCR Properties to undertake a Flood Risk Assessment of a development site at the current Chesser House car park in Gorgie Road, Edinburgh. A general site location plan is shown in Figure 1. The site is currently used as a car park for the adjacent building (Chesser House). The Water of Leith (WOL) flows north-east few meters to the west of the site. The Flood Risk Assessment considers the flooding risk from the WOL, Scottish Water systems, surface water runoff and groundwater. The scope of work includes the following. • Site visit and walkover survey; • Liaise with the Flooding Officer with a view to obtaining relevant information held by the council; • Review of historical maps; • Assess risk of flooding from WOL; • Prediction of surface water flooding risk based on site observations and available topographical data; • Assessment of overland flow paths through site; • Flood risk assessment from all likely sources (i.e. fluvial, pluvial, groundwater, surcharging sewer system); and • Reporting suitable for submission to support planning application, if all flood risk can be mitigated. Information made available to Kaya Consulting Ltd. for the study includes the following: • Location plan and development proposals; • Topographical survey of the site; • Mathematical model of the Water of Leith; • Scottish Water service drawings; • LiDAR DTM data; and • Water of Leith hydrological routing model. The work carried out to assess the flooding risk of the site and main findings of the study are summarised in the following sections. 1712-Chesser House Car Park, FRA SEP 19 V1.2 1 Kaya Consulting Ltd Figure 1: General site location Reproduced by permission of Ordnance Survey on behalf of The Controller of Her Majesty’s Stationery Office. © Crown copyright.