Determination of inundation areas within karst poljes and intermittent lakes for the purposes of ephemeral flood mapping
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PAPER
Determination of inundation areas within karst poljes and intermittent lakes for the purposes of ephemeral flood mapping Nataša Ravbar 1,2
&
Cyril Mayaud 1,2
&
Matej Blatnik 1,2
&
Metka Petrič 1,2
Received: 1 May 2020 / Accepted: 7 November 2020 # The Author(s) 2020
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. Keywords Karst . Groundwater/surface-water interaction . Intermittent lakes . Mapping procedure . Slovenia
Introduction 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” * Nataša Ravbar [email protected] Cyril Mayaud [email protected] Matej Blatnik [email protected] Metka Petrič [email protected] 1
ZRC SAZU, Karst Research Institute, Titov trg 2, 6230 Postojna, Slovenia
2
UNESCO Chair on Karst Education, University of Nova Gorica, Glavni trg 8, 5271 Vipava, Slovenia
composed. Water infiltrates rapidly and then flows through conduits and fissures underground (Hartmann et al. 2014). In special circumstances, such as areas of shallow karst and karst poljes, water overflows onto the surface and extensive groundwater/surface-water interaction occurs (Kovačič and Ravbar 2010; Naughton et al. 2012; Gutiérrez et al. 2014). Flooding follows periods of intense or long-lasting precipitation and as a result of groundwater-level r
