Historical Flood Map

The Historical Flood Map illustrates areas that are known to have flooded in the past.  The flooded area outlines depicted on this map have been generated from archived field data and aerial photographs that were collected by Rivers Agency at the time of the actual flood events.  Rivers Agency shall continue to capture data for all significant future flood events and this map shall be updated periodically as this new information becomes available.

However, we only have records for a relatively short period of time and many of the past floods cannot be linked to flood events with any particular return period.  Furthermore, flood alleviation schemes will have been undertaken at some of the flood prone locations which are highlighted on this map and this work will have significantly reduced the likelihood of future flooding at these areas.  As a consequence of these limitations this information does not provide a sound basis by which to estimate how likely it is that flooding will re-occur at a particular location in the future or for identifying flood prone areas that haven’t yet flooded.  In fact, it would require historical records that span many hundreds of years to produce reliable estimates of the magnitude and return period of potential future floods. However, the Historical Flood Map is useful insofar as it can serve as a strong visual reminder that the risk of flooding is very real.

To identify potential flood risk areas in a consistent and comprehensive manner across NI, it is therefore necessary to employ predictive modelling.   A range of predictive models have been used to estimate the extent of river and coastal flood plains and those areas likely to be susceptible to inundation by surface water.