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

66Planning Guidelines• The impact of flooding on a site including:- The likely rate at which flooding might occur (i.e. rapid onset orslow rise of flood water);- The speed of flow of flood water;- The order in which various parts of the location or site mightflood;- The likely duration of flood events;- The economic, social and environmental consequences of floodingon occupancy of the site.• Information on extent and depth of previous flood events or on floodpredictions;• An assessment of how safe access and egress can be provided for routineand emergency access under both frequent and extreme flood conditions;• An assessment of how the layout and form of development can be usedto reduce or minimise flood risk;• Proposals for surface-water management according to sustainabledrainage principles, with the aim of not increasing, and where practicable,reducing the rate of run-off from the site as a result of the development;• The likely impact of any displaced water on third parties caused byalterations to ground levels or raising flood embankments;• The potential impact on fluvial or coastal morphology and the likelylonger-term stability and sustainability of existing defences; and• The residual risks to the site after the construction of any necessarydefences and measures and the means of managing these risks. Thisshould include an assessment of whether the measures either designout the impacts of climate change or are adaptable to any increase inflood level.In addition to the requirements listed above, when completing a site-basedFRA as part of meeting the requirements of the Justification Test, an assessmentwill be required of on- and off-site opportunities for reducing flood riskoverall e.g. flood storage. This will include an appraisal of wider flood riskmanagement measures to which the development can contribute.An assessment of how surface water run-off will be managed should beaddressed in most FRAs. Drainage is a material consideration at the planningstage of a development and due consideration must be given to the impactof the proposed development on the catchment area. This includes anassessment of potential for both flood risk and pollution. Surface water runoffmay need to be assessed in all flood zones. The FRA should demonstratethat the surface-water drainage system takes account of SuDS principles, inaccordance with the design guidance referenced below. Where SuDS solutionsare not possible the FRA should identify the principles behind the chosenapproach and demonstrate that the method that gives the best environmentalprotection available at the site is adopted.