merrion street

The Geological Survey of Ireland (GSI) has commenced a three year project on groundwater flooding related to turloughs. This project will both provide an advisory service and also collect valuable flood data from high priority groundwater flooding sites in the Shannon Catchment and Gort lowlands. The GSI’s collaboration with local authorities and the Office of Public Works (OPW) will help to effectively understand the subsurface role in flood risk zones and assess potential solutions.
Groundwater flooding is an issue of significant importance with two record-breaking flood events occurring since 2009. Unlike river or coastal flooding, where the floods are concentrated along a river or coastline, groundwater flooding is more widespread and is controlled by regional and local geology. Groundwater flooding predominantly occurs in the karstified limestone of West and North-West of Ireland and has historically been most severe in the Gort lowlands in Co. Galway. Rural areas are predominantly impacted by floods, which are typically linked with seasonal lakes known as turloughs. Excessive flooding in turloughs rarely poses a risk to life but does cause damage to properties and prolonged disruption due to the relatively long flood duration. At present, a number of turloughs in Counties Roscommon and Longford are still severely inundated due to the high rainfall from November and December 2015.
Minister Denis Naughten TD congratulated the initiative saying, “The communities which have been affected by the devastating flooding events over the past number of winters will benefit from this cutting edge project over the next few years. An understanding of how these complex subsurface drainage systems work is crucial to managing the real life impact of Climate Change. “
Turloughs are complex subsurface systems, and each one behaves differently. It is therefore crucial to develop a better understanding of their flooding patterns so that they can be managed more effectively. Koen Verbruggen, Director of the Geological Survey of Ireland added “the GSI groundwater division has long been studying karst features, including turloughs, due to the critical role they play as potential pathways for pollution. This same approach and expertise can be readily enhanced, with additional resources and collaboration with Trinity College Dublin, to develop a monitoring programme and advisory service in relation to Groundwater flooding.”
Approximately 20 vulnerable sites will have fixed telemetric water level monitoring stations installed. Data from these stations will be assessed to monitor, understand and delineate groundwater flooding in Ireland. Aerial surveys such as LIDAR and UAV imagery will also be utilised to improve current groundwater flood mapping in hazard zones. Furthermore, satellite remote sensing data will used to provide up-to-date flood mapping for unmonitored turlough systems.
ENDS
Notes to the Editor:
· The Geological Survey of Ireland is the National Earth Science organisation and is a division of the Department of Communications, Climate Action and Environment (DCCAE). It is responsible for providing geological advice and information, and for the acquisition of data for this purpose. GSI produces a range of products including maps, reports and databases and acts as a knowledge centre and project partner in all aspects of Irish geology. www.gsi.ie.
· Turloughs are defined as ‘Topographic depressions in karst, which are intermittently flooded on an annual cycle via groundwater sources and have substrate and/or ecological communities characteristic of wetlands’ (WFD Groundwater Working Group, 2004). They require a moist climate and low lying limestone to occur, and they are virtually unique to Ireland. Over 400 turloughs are known to exist, and due to their unique flora and fauna, many are protected as Priority Habitats and Special Areas of Conservation by the EU Habitats Directive and ‘Groundwater dependent terrestrial ecosystems’ by the EU Water Framework Directive.
· The word ‘turlough’ comes from the Irish ‘tuar’ meaning dry and ‘lach’ meaning place (‘lach’ is often misspelled and thought to ‘loch’ meaning lake).