Groundwater flood hazards and mechanisms in lowland karst terrains

Abstract

The spatial and temporal complexities of flooding in karst terrains pose unique challenges in flood risk management. Lowland karst landscapes can be particularly susceptible to groundwater flooding due to a combination of low aquifer storage, high diffusivity and limited or absent surface drainage. Numerous notable groundwater flood events have been recorded in the Republic of Ireland throughout the twentieth century, but flooding during the winters of 2009 and 2015 was the most severe on record, causing widespread and prolonged disruption and damage to property and infrastructure. Effective flood risk management requires an understanding of the recharge, storage and transport mechanisms governing water movement across the landscape during flood conditions. Using information gathered from recent events, the main hydrological and geomorphological factors influencing flooding in these complex lowland karst groundwater systems are elucidated. Observed flood mechanisms included backwater flooding of sinks, high water levels in ephemerally flooded basins (turloughs), overtopping of depressions, and discharges from springs and resurgences. This paper addresses the need to improve our understanding of groundwater flooding in karst terrains to ensure efficient flood prevention and mitigation in the future, and thus helps to achieve the aims of the European Union Floods Directive.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

Exploring the Capability of Natural Flood Management Approaches in Groundwater-Dominated Chalk Streams

“…Despite a lack of surface-runoff generation in highly groundwater-dominated catchments, such as those in group 2, surface water can occur due to groundwater emergence. In this case, the water table rises to intersect with the ground surface, forming static pools of water in topographic low points called turloughs [74] and intermittently flowing river channels called winterbournes [75] and can activate springs in weak points and fractures in the chalk [20,76]. These phenomena generally occur after large quantities of prolonged rainfall.…”

“…Discharge rises slowly over the winter, peaking in late April after heavier winter rainfall, and gradually recedes over the summer, with lowest flows in autumn after generally drier summers. Groundwater flooding occurs when rainfall recharge causes the groundwater level to rise, in turn increasing groundwater inputs into river systems and causing groundwater emergence in topographic low points, winterbournes, and activating springs [19,20].…”

Groundwater rebound and flooding in the Naples' periurban area (Italy)

“…Based on Macdonald et al (2008), Hughes et al (2011), andNaughton et al (2017), it is possible to start from the GF scenarios to classify them as having either natural or anthropogenic origin (Table S2 in supplementary materials). In the first group (natural origin), it is possible to list: (i) flooding in alluvial lowlands, as a response of unconfined and consolidated aquifers to extreme rainfall events; (ii) flooding in small alluvial flatlands, as a response of shallow aquifers with limited storage capacity and good hydraulic connection with river networks to intense rainfall; (iii) flooding in alluvial deposits, caused by groundwater by-passing or circumventing river channel flood defense structures; (iv) flooding in lowland karst systems, induced by ephemeral karst lakes (turloughs) and/or intense groundwater discharge via springs, resurgences or shallow, highly permeable horizons within the epikarst; and (v) flooding in coastal lowland areas, driven by sea-level rise under climate changes or during and following severe storms.…”

Recent advances in karst research: from theory to fieldwork and applications

“…Lowland karst landscapes can be particularly susceptible to groundwater flooding due to a combination of low aquifer storage, high diffusivity and limited or absent surface drainage. Naughton et al (2017b) present a detailed example of the phenomenon of groundwater flooding in the lowland karst terrains of western Ireland following the dramatic floods that occurred during the winters of 2009 and 2015. These floods caused widespread damage and disruption to communities across the country, particularly in the extensive karstic limestone lowlands on the western seaboard (Naughton et al 2017a).…”