These focus on the potential effects that the floods could have on the four flood risk classifications.
- human health
- economic activity
- cultural heritage
- the environment
In particular, the maps show the number of people and the types of economic activity affected, and highlight the location of potentially polluting installations that may adversely impact on environmentally sensitive sites.
Flood maps were first published by DfI Rivers in November 2008.
This first generation of maps, known as the Strategic Flood Map (NI) Rivers & Sea, was developed to provide an indication of the general areas throughout Northern Ireland that may be prone to flooding from rivers and the sea.
A strategic surface water flood map was subsequently published in December 2011 and the name of the map service was changed to the Strategic Flood Map (NI).
Due to the onerous requirement to produce flood maps that cover the whole of the province, it was necessary to develop the strategic flood models using a broad-scale modelling methodology that had clear limitations.
These limitations meant the estimated floodplain outlines and inundation areas produced using the strategic models were not considered to be sufficiently accurate to determine the flood risk to a particular property or specific point location.
However, the initial objective of the strategic maps was to highlight the general areas and communities that were potentially at risk of flooding and they were entirely suitable for this purpose.
The Strategic Flood Map was used in the Preliminary Flood Risk Assessment for NI (PFRA) which was completed in December 2011 in compliance with the EU Floods Directive. A key objective of the PFRA was to identify areas of potentially significant flood risk for which detailed flood maps would be produced.
On the basis of the PFRA, it was determined that detailed flood maps should be produced for 20 Significant Flood Risk Areas and 49 Areas for Further Study and this work was completed as required by the EU Directive in December 2013.
In comparison with the strategic flood maps the accuracy and scope of the information illustrated in the detailed maps is greatly improved and most importantly (unlike the strategic maps) is considered suitable for determining the level of risk to individual properties and specific point locations.
The detailed maps for the 69 areas are now hosted within Flood Maps (NI).
For the geographical areas that are not covered by the detailed mapping the strategic flood maps will continue to be displayed within Flood Maps (NI).
Although the updating of flood mapping is normally an on-going process, the Directive requires Member States to complete a review of its mapping processes and to formally update flood hazard and risk maps. For the 2nd cycle, this review is required to be completed by December 2019.