COUNTY DEVELOPMENT PLAN 2016-2022 Appendix 13 Strategic Flood Risk Assessment 000000_DLR_Flood_Risk_Assmnt.indd 1 16/03/2016 07:55 000000_DLR_Flood_Risk_Assmnt.indd 2 16/03/2016 07:55 Contents 1 Background .......................................................................................................... 2 1.1 Introduction ............................................................................................................ 2 1.2 SFRA Structure ...................................................................................................... 2 2 The Planning System and Flood Risk Management ........................................ 3 2.1 Introduction ............................................................................................................ 3 2.2 Definition of Flood Risk .......................................................................................... 3 2.3 Definition of Flood Zones ....................................................................................... 4 2.4 Objectives and Principles of the Planning Guidelines ........................................... 4 2.5 The Sequential Approach and Justification Test ................................................... 5 2.6 Scales and Stages of Flood Risk Assessment ...................................................... 6 3 Strategic Flood Risk Assessment of Dún Laoghaire Rathdown .................... 8 3.1 Description of Study Area ...................................................................................... 8 3.2 Identification of Flood Risk (Stage 1) ..................................................................... 8 3.3 Summary of flood sources ..................................................................................... 10 4 Policy Response .................................................................................................. 15 4.1 The Strategic Approach ......................................................................................... 15 4.2 Development Management and Flood Risk .......................................................... 17 4.3 Requirements for a Flood Risk Assessment ......................................................... 17 4.4 Drainage impact assessment ................................................................................ 17 4.5 Development proposals in Flood Zone C .............................................................. 18 4.6 Applications for Minor Developments in Areas at Risk of Flooding ....................... 18 4.7 Applications for Larger Development in Areas at Risk of Flooding ....................... 19 4.8 Key points for FRAs for all types of development ................................................. 20 4.9 Incorporating Climate Change into Development Design ..................................... 21 4.10 Flood Mitigation Measures at Site Design ............................................................. 21 4.11 'Green Corridor' ..................................................................................................... 23 5 Application of the Justification Test .................................................................. 24 5.1 Undeveloped land .................................................................................................. 24 5.2 Existing, developed, zoned areas at risk of flooding ............................................. 24 5.3 Justification Test: Part 3 ........................................................................................ 25 6 SFRA review and monitoring ................................................................................. 38 7 Glossary ............................................................................................................... 39 Annexes ............................................................................................................................. I A Dundrum Shopping Centre ................................................................................. I final copy SFRA 000000_DLR_Flood_Risk_Assmnt.indd 3 16/03/2016 07:55 List of Figures Figure 2-1 Sequential Approach Principles in Flood Risk Management ........................... 5 Figure 5-1: Crinken Stream ................................................................................................ 26 Figure 5-2: Old Conna LAP ................................................................................................ 27 Figure 5-3: Shanganagh and Deansgrange Rivers ............................................................ 29 Figure 5-4: Loughlinstown River ......................................................................................... 30 Figure 5-5: Seafield and Bayview ....................................................................................... 31 Figure 5-6: Carrickmines River ........................................................................................... 31 Figure 5-7: Carysfort Maretimo Rivers ............................................................................... 32 Figure 5-8: Merrion Strand to Blackrock ............................................................................. 33 Figure 5-9: Dundrum Slang ................................................................................................ 34 Figure 5-10: River Dodder .................................................................................................. 36 Figure 5-11: Little Dargle .................................................................................................... 36 List of Tables Table 2-1 Probability of Flooding ....................................................................................... 3 Table 2-2 Definition of Flood Zones .................................................................................. 4 Table 2-3 Matrix of Vulnerability versus Flood Zone ......................................................... 6 Table 3-1: Flood Risk Datasets .......................................................................................... 9 Table 3-2: Allowances for Future Scenarios (100 Year Time Horizon) .............................. 13 Table 5-1: Justification Test (Part 1 and 2) only for zoning objective A, A1, A2, NC, DC, MTC, E,TLI, MH, MIC, MOC, OE, W areas in the County that are already developed and include existing vulnerable uses and are in flood zone A and B. .................................................................................................... 25 Table 5-2: Justification test for Old Conna ......................................................................... 27 Table 6-1: SFRA Review Triggers ...................................................................................... 38 final copy SFRA 000000_DLR_Flood_Risk_Assmnt.indd 4 16/03/2016 07:55 IMPORTANT DISCLAIMER Dún Laoghaire-Rathdown Strategic Flood Risk Assessment Please read below the disclaimer, and limitations associated with this assessment to avoid incorrect interpretation of the information and data provided. DISCLAIMER Dún Laoghaire-Rathdown County Council makes no representations, warranties or undertakings about any of the information provided in this assessment including, without limitation, on its accuracy, completeness, quality or fitness for any particular purpose. To the fullest extent permitted by applicable law, Dún Laoghaire-Rathdown nor any of its members, officers, associates, consultants, employees, affiliates, servants, agents or other representatives shall be liable for loss or damage arising out of, or in connection with, the use of, or the inability to use, the information provided in this assessment including, but not limited to, indirect or consequential loss or damages, loss of data, income, profit, or opportunity, loss of, or damage to, property and claims of third parties, even if Dún Laoghaire-Rathdown has been advised of the possibility of such loss or damages, or such loss or damages were reasonably foreseeable. Dún Laoghaire- Rathdown reserves the right to change the content and / or presentation of any of the information provided in this report at their sole discretion, including these notes and disclaimer. This disclaimer, guidance notes and conditions of use shall be governed by, and construed in accordance with, the laws of the Republic of Ireland. If any provision of these disclaimer, guidance notes and conditions of use shall be unlawful, void or for any reason unenforceable, that provision shall be deemed severable and shall not affect the validity and enforceability of the remaining provisions. UNCERTAINTY Although great care and modern, widely-accepted methods have been used in the preparation of this assessment there is inevitably a range of inherent uncertainties and assumptions made during the estimation of design flows and the construction of flood models. BEST AVAILABLE INFORMATION There has been a wide range of datasets utilised in the production of this plan which are constantly changing and subsequently the analysis of these datasets is only correct at the time of assessment. The assessment is based on the maps available in June 2015 (which includes Draft Eastern CFRAM maps). It is acknowledged that new methodologies and/or recently recorded data could have a minor impact on the analysis undertaken herein. The SFRA is not a statutory planning document. It is a consultation document that should be used to inform a development plan or local area plan, enabling the implementation of the „Sequential Approach‟‟ and the testing of development zoning against flood risk