The Planning System and Flood Risk Management - Offaly County ...

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54Appendix A - Screening for andCarrying out the Flood RiskAssessment1 FLOOD RISK ASSESSMENTPlanning Guidelines1.1 OverviewFlood risk assessments (FRAs) aim to identify, quantify and communicate todecision-makers and other stakeholders the risk of flooding to land, propertyand people. The purpose is to provide sufficient information to determinewhether particular actions (such as zoning of land for development, approvingapplications for proposed development, the construction of a flood protectionscheme or the installation of a flood warning scheme) are appropriate.This Appendix seeks to explain the terminology and the methodology offlood risk assessment so that decision-makers can consider such assessmentsin an informed manner. It does not seek to duplicate the abundant guidancethat is available from other sources but makes appropriate reference to suchguidance.A flood risk assessment (FRA) can be undertaken either over a large area orfor a particular site to:• assess whether flood risk is an issue for the area, and if so, to whatdegree;• identify flood zones (if not already available);• inform decisions in relation to zoning and planning applications;• develop appropriate flood risk mitigation and management measuresfor development sited in flood risk areas.FRAs can be undertaken at a range of scales relevant to the planning process,as discussed in more detail in Section 1.4 herein. The key scales of FRA are:• Regional for (Regional Planning Guidelines);• Strategic for City or County Development Plans or Local Area Plans);• Site Specific (for master plans and individual site planning applications).FRAs are typically undertaken over a number of stages, with the need forprogression to a more detailed stage dependent on the outcomes of the formerstage.1.2 General Principles of Flood Risk AssessmentWith all FRAs undertaken for land-use change and new developments, thereare some general principles that are applicable and should be followed. Theseare noted below:
• FRAs should be proportionate to the risk and appropriate to the scale,nature and location of the development.• FRAs should be undertaken by competent people, as early as possiblein the particular planning process. Use should be made of a suitablyqualified hydrologist, flood risk management professional or specialistwater engineer, with the appropriate skills and experience to undertakea flood risk assessment.• FRAs should be supported by appropriate data and information, includinghistorical information on previous events, but focusing more on predictiveassessment of less frequent or more extreme events. The FRA must takethe likely impacts of climate change into account.• FRAs must address the impact of a change in land use or developmenton flood risk elsewhere. Any such change or development must notadd to and should, where practicable, reduce flood risk.• FRAs must consider the vulnerability of those that could occupy thedevelopment, including arrangements for safe access and egress.• FRAs should consider the modification to flood risk that infrastructuresuch as raised defences, flow channels, flood-storage areas and otherartificial features provide, together with the consequences of their failure.1.3 Source-Pathway-Receptor ModelThe assessment of flood risk requires a thorough understanding of the sourcesof flood water (e.g. high sea levels, intense or prolonged rainfall leading torun-off and increased flow in rivers and sewers), the people and assets affectedby flooding (known as the receptors) and the pathways by which the floodwater reaches those receptors (e.g. river channels, river and coastal floodplains,drains, sewers and overland flow).The source-pathway-receptor (S-P-R) model has become widely used toassess and inform the management of environmental risks. This isillustrated in Figure A1. FRA thus requires identification and assessment ofall three components:• The probability and magnitude of the source(s) (e.g. high river levels,sea levels and wave heights).• The performance and response of pathways and barriers to pathwayssuch as floodplain areas and flood defence systems.• The consequences to receptors such as people, properties and theenvironment.55Planning Guidelines
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At the site-specific level, develop
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Planning Guidelines
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2regard to the guidelines in the pe
Page 14 and 15: 4Planning GuidelinesReport of the F
Page 16 and 17: 6Chapter 2:Flooding - Key ConceptsP
Page 18 and 19: 82.5 Increase in flooding due to de
Page 20 and 21: 10Flood risk2.13 Understanding floo
Page 22 and 23: 122.21 In undertaking a flood risk
Page 24 and 25: 142.30 Increases in rainfall intens
Page 26 and 27: 16after periods of heavy rainfall.
Page 28 and 29: 18that also meet the objectives of
Page 30 and 31: 20more than 1 in 200). Development
Page 32 and 33: 22Government under Section 28 of th
Page 34 and 35: 24Planning GuidelinesDevelopment in
Page 36 and 37: 26Chapter 4:Flooding and Spatial Pl
Page 38 and 39: 28floodplain. Effective co-ordinati
Page 40 and 41: 30Planning GuidelinesFig. 4: Develo
Page 42 and 43: 32• Include zoning objectives to
Page 44 and 45: 34specific areas, ensuring that flo
Page 46 and 47: 36should use the flood risk informa
Page 48 and 49: 38planning authority to ensure that
Page 50 and 51: 40• these guidelines, and in part
Page 52 and 53: 425.22 Where development proposals
Page 54 and 55: 44Chapter 6:ConclusionPlanning Guid
Page 56 and 57: 46TermsDefinitionPlanning Guideline
Page 66 and 67: 56Climate changeincreased intensity
Page 68 and 69: 58Strategic assessments provide the
Page 70 and 71: 60As part of a FRA, information on
Page 72 and 73: 62A successful FRA is characterized
Page 74 and 75: 64• Suggested policies for sustai
Page 76 and 77: 66Planning Guidelines• The impact
Page 78 and 79: 68An additional document on interpr
Page 80 and 81: 70Table A2: The Flood Risk Balance
Page 82 and 83: 72Appendix B - Addressing FloodRisk
Page 84 and 85: 74Figure B2 below illustrates how t
Page 86 and 87: 76drainage processes and removing p
Page 88 and 89: 78• Signing of floodplain areas s
Page 90 and 91: 80flood level. Care must be taken t
Page 92 and 93: 82Appendix C - Frequently AskedQues
Page 94 and 95: 84What does the SFRA not provide?Th
Page 96 and 97: 86pressure in the embankment and ge
Page 98: Printed on recycled paper containin
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