Floods are a natural and inevitable part of life in Ireland, that can have a significant impact on property, people, communities, the environment, and cultural heritage. Flooding is usually a result of natural causes including massive rainfall, overflowing of the rivers and blocked or overloaded drainage ditches. Numerous severe floods have occurred throughout the country in the last decade, and the frequency pattern and severity of flooding is expected to increase as a result of climate change.

A site-specific Flood Risk Assessment (FRA) is required in accordance with the OPW document “The Planning System and Flood Risk Management” when the local authority considers there is a risk of flooding. These Guidelines contributes to the avoidance or minimisation of potential flood risk through a more systematic approach within a river catchment context.

There are three different stages of a Flood Risk Assessment.

Stage 1 – Flood Risk Identification

Identify whether there may be any flooding or surface water management issues related to either the area of regional planning guidelines, development plans and LAP’s or a proposed development site.

Stage 2 – Initial Flood Risk Assessment

Confirm sources of flooding that may affect the proposed development site, appraise both flood risk at the site and the potential impacts of the proposed development on flooding elsewhere and scope the extent of the risk of flooding which may involve preparing indicative flood zone maps.

Stage 3 – Detailed Flood Risk Assessment

A level 3 report is only undertaken if the previous stages determine the need for a detailed analysis of the flood risk issues at the proposed development which may include hydraulic modelling of adjacent watercourses and consideration of proposed surface water drainage arrangements. Hydraulic modelling using software such as FloodModeller and HEC RAS will be prepared to quantify flood risk to the site, and the impact of the development and proposed mitigation elsewhere.

At TOBIN Consulting Engineers, our Water Services Team provides integrated and sustainable solutions to help our clients understand and manage flood risk. Due to our wealth of experience in this field, we have a strategic knowledge of the flood risk issues relevant to the study location at the outset, ensuring that our time is targeted at the most salient flood risk issues, thus providing the maximum benefit for our clients’ investment.

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