Abstract
The karst environment presents a special challenge when it comes to identifying groundwater/surface-water interactions. Existing definitions of areas of regular flooding in karst regions are too general and lack a measurable approach for the determination of flood-liable land. This paper proposes a means of specific definition and quantitative determination of intermittently flooded karst areas, which takes into account the extent, duration and frequency of flooding, and includes the identification of data sources and processing methods. The procedure, involving spatial layers, was developed using a pilot area and tested in three additional areas in Slovenia. The derived definition determines that flood-liable land within karst poljes and intermittent lakes comprise areas where stagnant water or stream overflow is present for at least 10 days/year over a period of 30 years, and these waters have direct contact with groundwater. The results show that the proposed procedure is applicable to areas with different geomorphological settings and to areas where the quantity and quality of available data vary. The study is an example of the practical application of knowledge on karst, as the findings can be used for short-term purposes (mapping flood areas, determination of habitats) and long-term purposes (study of impacts of environmental changes). Attention should be drawn to the lack of available data and the fact that the national networks of hydrological observatories are often too sparse for this purpose. This study raises awareness of these shortcomings and improves the planning or expansion of such a network in collaboration with experts.
Highlights
Surface water flow is usually not present in karst areas because of the high porosity of the rock of which they are Published in the special issue “Five decades of advances in karst hydrogeology”
Intermittent lakes in karst areas are characteristic of Ireland, where they are known as “turloughs”, and they occur in Spain, Italy, Estonia, Canada, the states of Tennessee and Kentucky in the USA, the provinces of Guangxi, Guizhou and Yunnan in China, Minas Gerais state in Brazil, and elsewhere (Auler 1995; López-Chicano et al 2002; Milanović 2004; Sheehy Skeffington et al 2006; Zhou 2007; Simpson and Florea 2009; Naughton et al 2012; Parise 2015)
Owing to the complexity of hydrodynamics, defining areas that are frequently subject to flooding represents a unique challenge for the designers of various water policies and management mechanisms for the protection of special habitats, in part because of a lack of temporal and spatial information on flooding and limited understanding of local hydrogeological conditions
Summary
Flooding follows periods of intense or long-lasting precipitation and as a result of groundwater-level rise in a karst aquifer. Such aquifers are normally characterised by high spatial heterogeneity, highly diffusive flow and a low level of water storage. Water floods the ground surface when the inflow of water exceeds the capacity of underground drainage channels. Along surface watercourses, this causes a backflooding effect and overflow along the length of stream channels. Numerous karst poljes in the Dinaric Karst of Europe are known for causing the intermittent presence of surface water. Intermittent lakes in karst areas are characteristic of Ireland, where they are known as “turloughs”, and they occur in Spain, Italy, Estonia, Canada, the states of Tennessee and Kentucky in the USA, the provinces of Guangxi, Guizhou and Yunnan in China, Minas Gerais state in Brazil, and elsewhere (Auler 1995; López-Chicano et al 2002; Milanović 2004; Sheehy Skeffington et al 2006; Zhou 2007; Simpson and Florea 2009; Naughton et al 2012; Parise 2015)
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