Flood protection with dams and flood control reservoirs—before and after the extreme flood event of August 2002, Saxony

Abstract

This paper presents the flood design and the effects of Saxony dams before, during and after the extreme flood event in 2002. As the Saxony dams were exposed to an extraordinary load situation (at some dams the 10 000 year design flood was exceeded) during the 2002 flood event, this paper aims to highlight the problems and damages connected to such an extreme event. The second part demonstrates with concrete examples (bypass tunnel, enlargement of bottom outlet and spillway capacities, enlargement of flood retention storage), how the management and design of the Saxony dams were changed based on the analysis of the extreme flood and consideration of new hydrological boundary conditions. In this context, the limits and potential conflict, particularly concerning multipurpose reservoirs, will be described. The last part presents an insight to the Saxony approach to determine new sites for flood control reservoirs. Immediately after the flood event in August 2002, approximately 200 potential sites have been identified. With the availability of flood protection concepts, feasibility studies for 74 potential sites have been carried out. A focal point for these assessments was to conduct cost–benefit analyses. The establishment of appropriate damage functions was the main challenge during the assessments. Hydrological, engineering and environmental investigations and the related conflict potential are also described. As a result of the feasibility studies, 13 flood retention reservoirs are currently designed and scheduled for implementation in Saxony.