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

58Strategic assessments provide the level of spatial resolution which is appropriateto the scale of the flood risk. Strategic should not be mistaken for ‘broadbrush’ or high level. Often a mosaic of techniques should be used across anarea, so that the uncertainties on the spatial extent of flooding are reducedto an appropriate level for the decision being made. The greatest contributionto reducing that uncertainty is an accurate digital elevation model of floodplaintopography.Planning GuidelinesSFRAs will provide more detailed information on the broad spatial distributionof flood risk within extensive areas of high flood risk where development isto be considered, and also where it will be necessary to apply the JustificationTest. The information may also be used to assess how any environmentalobjectives relating to flooding, as defined in the strategic environmentalassessment, may be affected by change in land use and/or additionaldevelopment.In local authority areas where flooding is not a major issue and wheredevelopment pressures are low, a less detailed approach will be requiredrelative to that necessary in areas where there is high development pressureand flooding is a significant issue. This will be apparent through the stagedapproach to planning an assessment. This approach is recommended toallow flexibility in the level of assessment required from one local authorityarea to another.Where the requirements of the Justification Test need to be satisfied, a detailedassessment should be undertaken to consider the nature of flood hazard,taking account of the presence of flood risk management measures such asflood protection schemes. Such schemes and other infrastructure, which actsas a flood defence, can significantly affect the risk factors and the followingindicators that are used in a FRA:• Flood probability;• Flood depth;• Flood velocity;• Rate of onset of flooding.1.5 Stages in the Assessment of Flood RiskWithin the planning system flood risk will need to be integrated into theplan-making process. The steps in the Development Plan process and itsStrategic Environmental Assessment needs to be supported by appropriatestudies into flood risk. This is shown in the flow chart in Section 4 of theGuidance.The are three principle stages to Flood Risk Assessment. Step 1 - Screening:Step 2 – Scoping: Step 3 - Assessing.