Groundwater flooding

​​​Groundwater flooding occurs when the water table rises above the land surface. It generally requires sustained rainfall over relatively longer duration than other forms of flooding, its location is discontinuous, and they can last for weeks or months. The increased frequency of groundwater flooding in Ireland in recent decades has highlighted the need to better understand, map and monitor groundwater flood events. In this context Geological Survey Ireland initiated the GWFlood project in 2016 in order to address the deficit of data and fit-for-purpose flood maps. With the GWFlood project now complete, our work on groundwater flooding is now advancing through the newly established GWClimate project which is developing flood forecast tools and evaluate the potential impacts of climate change to groundwater flooding (and groundwater drought).

 

What is groundwater flooding

​Groundwater flooding occurs when a natural underground drainage system is incapable of sufficiently draining itself, resulting in the emergence of groundwater at the surface. In Ireland, the most extensive form of groundwater flooding is related to prolonged rainfall causing water table rise in the limestone lowland areas in the west of the country.

GWFlood project (2016-2019)

​GWFlood was a groundwater flood monitoring and mapping project aimed at addressing the knowledge gaps surrounding groundwater flooding in Ireland. The project was initiated in response to the unprecedented groundwater floods of Winter 2015/2016 and was a collaborative effort combining the karst groundwater expertise of Geological Survey Ireland,  Trinity College Dublin and the IT Carlow.

GWClimate project (2020-2022)

​Climate change will undoubtedly have an impact on groundwater flooding in Ireland. Over the coming decades climate change may alter the severity, frequency and duration of flood events. Through the GWClimate project, the impacts of climate change groundwater flooding and groundwater drought will be monitored and investigated. 

Groundwater level monitoring network

Geological Survey Ireland has established a network of permanent monitoring stations providing real-time information on water levels at key sites which are representative of the spectrum of groundwater flooding conditions in Ireland.

Historic groundwater flood map

​The historic groundwater flood map is a national-scale flood map presenting the maximum historic observed extent of groundwater flooding in limestone regions. The map is primarily based on the winter 2015/2016 flooding event. 

Predictive groundwater flood map

​A national predictive groundwater flood map was developed for limestone regions, including over 500 groundwater flooding areas. The map shows the probability of a flood event occurring in any year assuming current climate conditions.