Indicative Flood Zone Mapping

In November 2009 Mr. John Gormley, T.D., Minister for the Environment, Heritage and Local Government published statutory planning guidelines entitled The Planning System and Flood Risk Management: Guidelines for Planning Authorities, which is aimed at providing a more consistent, rigorous and systematic approach to the avoidance and minimisation of potential future flood risk and to fully incorporate flood risk assessment and management into the planning system.

 

In accordance with these guidelines South Tipperary County Council commissioned JBA, one of Ireland's leading specialists in flood risk and environmental management, to produce an indicative flood zone map.

 

The flood zones are indicative of river and coastal flooding only and should be used as an information source when matching appropriate land use with the level of flood risk . The indicative flood risk zones should not be used to suggest that any areas are free from flood risk, since they do not include the effects of other forms of flooding such as from groundwater or artificial drainage systems and because of the methodology used.

 

There are three indicative flood risk zones based on international standards: and the central tenant of the approach to be undertaken, as set out in The Planning System and Flood Risk Management Guidelines for Planning Authorities, is to use the information provided in the mapping as a site selection tool prior to making a decision on applying for planning permission at any particular site.

 

Zone  Risk  Description 
Zone A High Probability of Flooding This zone defines areas with the highest risk of flooding from rivers (i.e. more than 1% probability or more than 1 in 100) and the coast (i.e. more than 0.5% probability or more than 1 in 200).
Zone B Moderate Probability of Flooding This zone defines areas with a moderate risk of flooding from rivers (i.e. 0.1% to 1% probability or between 1 in 100 and 1 in 1000) and the coast (i.e. 0.1% to 0.5% probability or between 1 in 200 and 1 in 1000).
Zone C Low Probability of Flooding This zone defines areas with a low risk of flooding from rivers and the coast (i.e. less than 0.1% probability or less than 1 in 1000).

The Flood Map is a mathematical model to provide clarity on the flooding risk associated with fluvial (and coastal) flooding events of a magnitude of 1 in 100 yr return; 1 in 1000 yr return and greater than 1 in 1000 yr return. The Map is not intended to provide a site specific flood risk assessment. Site specifice flood risk assessment can only be ascertained on a case by case basis.

The map was generated on a grid of 10m2 cells, based on the resolution of the digital terrain model. It is therefore recommended that the outlines are displayed on 1:50,000 scale mapping (Discovery series). At smaller scales the mapping will begin to appear distorted; the mapping is not designed to be viewed at the individual residence, or even street, scale.  For this reason the flood zones are not visible when the map is at a scale of 1:10000 or greater

The attached document “Introduction to JBA’s Flood Maps”  provides an overview of the mapping, including methodology and purpose for which they are intended to be used.

(PDF Logo 248 kbs) Introduction to JBA’s Flood Maps

Prior to making an assessment or forming an opinion on flood risk, based on the JBA Mapping you are advised to consider the principles informing the risk-management based approach set out in the The Planning System and Flood Risk Management: Guidelines for Planning Authorities and you are further advised to have regard to the advice  provided by the Office of Public Works, the lead agency for flood risk management in Irelan at. www.opw.ie/en/FloodRiskManagement/