Combining hydraulic model, hydrogeomorphological observations and chemical analyses of surface waters to improve knowledge on karst flash floods genesis

Abstract

Abstract. During a flood event over a karst watershed, the connections between surface and ground waters appear to be complex ones. The karst may attenuate surface floods by absorbing water or contribute to the surface flood by direct contribution of karst waters in the rivers (perennial and overflowing springs) and by diffuse resurgence along the hillslopes. If it is possible to monitor each known outlet of a karst system, the diffuse contribution is yet difficult to assess. Furthermore, all these connections vary over time according to several factors such as the water content of the soil and underground, the rainfall characteristics, the runoff pathways. Therefore, the contribution of each compartment is generally difficult to assess, and flood dynamics are not fully understood. To face these misunderstandings and difficulties, we analysed surface waters during six recent flood events in the Lirou watershed (a karst tributary of the Lez, in South of France). Because of the specific chemical signature of karst waters, chemical analyses can supply information about water pathways and flood dynamics. Then, we used the dilution law to combine chemical results, flow data and field observations to assess the dynamics of the karst component of the flood. To end, we discussed the surface or karst origin of the waters responsible for the apparent runoff coefficient rise during flash karst flood.

Classification of karst springs for flash-flood-prone areas in western Turkey

“…As a matter of fact, Shuster and White (1971), Atkinson (1977), Aydin (2005) and Demiroglu (2008) argued that the reason for the change observed in the spring discharges was the recharge type or flow type (diffuse or conduit) with high or low storage. A high number of studies have been done to define aquifer characteristics using physicochemical measurements (Shuster and White, 1971;Raeisi and Karami, 1997;Massei et al, 2007;Raynaud et al, 2015) by considering only one or a few physico-chemical parameters that characterize groundwater, which has the potential to lead to an erroneous interpretation of the hydrodynamics of the karstic catchment draining into the spring (Chicanoa et al, 2001;Massei et al, 2007). This study aims to classify karst aquifers based on their response to heavy rainfall events, by using a hydrogeochemical approach, assessing data from several springs in different carbonate rock in western Turkey.…”

Magnesium as Environmental Tracer for Karst Spring Baseflow/Overflow Assessment—A Case Study of the Pertuso Karst Spring (Latium Region, Italy)

“…In fact, karst springs discharge is not easily measurable by standard techniques or conventional instruments, even due to the extremely high variability of the parameter. Moreover, in case of extreme rainfall events, overflow springs are activated when the conduit carrying capacity is exceeded and depending on the conduit system geometry [29,30]. In this case, total discharge may be underestimated.…”

Classification of Karst Springs For Flash Flood-Prone Areas in Western Turkey

“…Infiltration has two different forms: areal or spatial diffusive infiltration flows, passing directly into the groundwater reservoir. The spatial groundwater recharge process is diffusive, in which water reaches the groundwater table as a laminar flow through the intergran-ular unfractured bedrock and fractures (Shuster and White, 1971). The other form of recharge (point infiltration) passes via karst structures, such as caves and sinkholes.…”

“…As a matter of fact, Shuster and White (1971), Atkinson (1977), Aydin (2005) and Demiroglu (2008) argued that the reason for the change observed in the spring discharges was the recharge type or flow type (diffuse or conduit) with high or low storage. A high number of studies have been done to define aquifer characteristics using physicochemical measurements (Shuster and White, 1971;Raeisi and Karami, 1997;Massei et al, 2007;Raynaud et al, 2015) by considering only one or a few physico-chemical parameters that characterize groundwater, which has the potential to lead to an erroneous interpretation of the hydrodynamics of the karstic catchment draining into the spring (Chicanoa et al, 2001;Massei et al, 2007). This study aims to classify karst aquifers based on their response to heavy rainfall events, by using a hydrogeochemical approach, assessing data from several springs in different carbonate rock in western Turkey.…”