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Flood Risk Assessment

Flood Risk Assessment

Flood Risk Assessments (FRA) are now a design and planning consideration for small and large scale developments. Flood planning policy is set out in “The Planning System and Flood Risk Management – Guidelines for Planning Authorities 2009”. The policy aims to incorporate flood risk identification, assessment and management into the planning process thus avoiding unsuitable development in flood zones.

Geoenvironmental Ltd are able to provide detailed Flood Risk Assessments for residential or commercial developments of any scale, nationwide. The susceptibility of land to flooding is an increasingly important consideration in determining planning applications; the potential consequences for occupiers, either of the development or elsewhere, in terms of property damage, safety and financial risk can be serious. Local Authorities require site specific flood risk assessments to be carried out where previous mapping carried out by other consultants or by the OPW has identified a potential flood risk. Flood Risk Assessment needs to be rigorous in its approach to pass the scrutiny of Local Authorities. Flood Risk Assessments (FRAs) vary from simple exercises for small or less vulnerable developments to detailed studies for more vulnerable or larger developments, sometimes requiring quantitative approaches i.e. hydraulic modelling to determine the risk posed to the development.

Geoenvironmental Ltd offer various levels of detail suited to your requirements Flood risk assessments (FRA) can vary in complexity and scale and be assessed using the following stages:

Stage 1: Flood risk identification

To identify whether there may be any flooding or surface water management issues related to the site and to give an early assessment to base further recommendations on.

Stage 2: Initial flood risk assessment

A Phase 2 assessment expands on the stage 1 assessment and includes the following;

  • Appraisal of existing flood risk information.
  • Pluvial Flood Risk (Flood risk in low-lying areas as a result of excessive rainfall)
  • Qualitative review of flood risk posed to the site.
  • Examination of the potential impacts the development will have on flooding elsewhere.
  • Production of a Flood Risk Assessment Report including possible flood risk mitigation measures which would reduce flood risk to acceptable levels

Stage 3: Detailed flood risk assessment

A Level 3 assessment is a quantitative assessment of potential flood events. It is undertaken if the previous stages determine the need for quantitative analysis to assess flood risk issues relating to the development site and may include;

  • Topographic survey of the river channel and surrounding ground levels/floodplains,
  • Hydrological assessment of the subject catchment,
  • Calculation of Stream and or river catchment area and extreme discharge flows
  • Hydraulic calculations and modelling to quantify the flood risk to the site,
  • Assessment of flood risk upstream and downstream,
  • Review of existing and proposed surface water drainage and
  • Recommend appropriate flood risk mitigation measures.

If you require a design phase FRA or need to respond to a ‘further Information’ request from a planning section, call and speak to Geoenvironmental Ltd today.