Flood Risk Assessment requirements for development in fluvial/coastal flood plain

When the proposed development is within the fluvial / coastal flood plain22 The FRA in these circumstances will typically be required to contain the following information relating to the Assessment of the Flood Risk: • A location plan as detailed under paragraph D6; • A site plan (and where appropriate, cross sections) showing pre-development and post-development levels related to Ordnance Datum Belfast, existing structures, development proposals, watercourses in or bounding the site, internal site drainage and drainage outfalls; • Details of any existing or proposed flood alleviation measures or flood defence structures that may influence the site including information on their structural condition, level of protection and maintenance regime; • The identification of all sources of flooding pre and post- development; • An assessment of the hydraulic capacity and structural integrity of all drains and sewers within or bounding the site. The methodologies for assessment must be clearly identified; • Data on historical flooding events accompanied by supporting information as detailed under paragraph D6; • A plan of the site showing the extent of the predicted Q100 / Q200 flood plain and / or in the case of a reservoir, the extent of the predicted flood inundation area. This will involve the production of hydraulic models requiring longitudinal / cross sections of the watercourse and the site, assessment of flood discharges using industry standard methodologies, and the inclusion of information such as finished floor levels, access road and car park levels, estimated flood water levels, flood depths and velocities and associated probability of flooding; • A plan and description of features which may influence local hydraulics. For example, bridges, pipes or ducts crossing watercourses, culverts, embankments and walls; • An assessment of the likely speed of potential flooding, the sequence in which various parts of the site may flood, the likely duration of a flood event, the potential consequences of a flood event, the depth and velocity of flood water;