Lee Catchment Flood Risk Assessment and Management Study

Lee CFRAMS Home > Work schedule > Flood mapping > Flood extent mapping

Flood extent mapping

Flood extent maps illustrate the estimated area inundated by a particular flood event for a given annual exceedence probability (AEP). The AEP is a statistical measurement indicating the likelihood of a flood event of a certain intensity occurring or being exceeded in any given year. Thus a 10% AEP describes a flood event which has a 10% chance of occurring or being exceeded in a given year. Flood extent maps have been produced for the 50%, 10%, 5%, 2%, 1%, 0.5%, 0.2% and 0.1% AEP.

Flood extent maps are produced using a combination of the hydraulic model results and a Digital Terrain Model (DTM) of the catchment developed from the LiDAR survey of the floodplains. Draft flood extent maps for the lee catchment are available to view at the following link.

The shaded blue areas on the maps show the extent of flooding from a fluvial flood for a given AEP. The shaded green areas show the extent of flooding from a tide and storm surge event for a given AEP. The dotted and solid lines surrounding the shaded areas show the level of uncertainty associated with a given flood extent. As part of the Lee CFRAM Study, Halcrow have undertaken a research project on behalf of the OPW to test and calibrate a method for determining uncertainty in the flood extent maps.


Carrigadrohid Castle

Lough Allua

River Lee at Tivoli

Key Activities

The key activities to the project are

Latest news

Final edition of Lee CFRAMS newsletter (more)

Consultation on the SEA Environmental Report (more)

Non-Technical Summary for SEA Environmental Report published(more)

Consultation on the draft Flood Risk Management Plan (more)

Consultation on Lee Predictive Floodmaps (more)