Modelling groundwater flooding in a lowland karst catchment

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Publication Date

1-1-2020

Publication Title

Journal of Hydrology

Volume Number

580

Abstract

Groundwater flooding is a phenomenon which has become recognised as a significant natural hazard in recent years. The Gort lowland karst catchment situated in south Co. Galway on the western coast of Ireland has experienced two extreme groundwater flood events in the past decade leading to considerable damage and disruption. Groundwater flooding in the catchment typically occurs following periods of sustained heavy rainfall when sufficient capacity is not available in the bedrock to store and convey water to the sea. The underground karst conduit system therefore surcharges to the ground surface through a system of estavelles and floods low-lying areas of ground known as turloughs (ephemeral lakes). A 1D/2D pipe network model of the karst conduit system of the Gort lowland karst was developed in order to simulate the flooding mechanisms across the catchment as well as to assess flood alleviation options. The nature of the underground karstic connections in the system has been determined from a combination of available field data (dye tracing, water chemistry data etc.) and cross-frequency analysis on the turlough fluctuation time series data over several years. The availability of high accuracy LiDAR data of the catchment then allowed the flooding regime to be accurately simulated on the ground surface. The model was calibrated using historic continuous water level data for a number of turloughs in the catchment and then validated using historic peak spot flood levels. The model was then used to identify appropriate potential groundwater flood alleviation measures for the catchment. The impacts of such measures on both the salinity of Kinvara bay, through increased freshwater discharges, and eco-hydrology of the protected wetland habitats within the turloughs was also investigated. The study demonstrated that the measures proposed can be developed without inducing undesirable impacts to either salinity in Kinvara Bay (and thus mariculture) or to the protected turlough habitats. The study has also demonstrated the suitability and functionality of such karst models for examining groundwater flood management options and eco-hydrology in karst catchments.

Keywords

Karst, Groundwater flooding, Hydrologic models, Flood control, Wetland ecology

Document Type

Article

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.jhydrol.2019.124361

Language

English

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