Sediment Dynamics and the Hydromorphology of Fluvial Systems (Proceedings of a symposium held in 72 Dundee, UK, July 2006). IAHS Publ. 306, 2006. The life-span of a small high mountain lake, the Vordere Blaue Gumpe in the Bavarian Alps DAVID MORCHE1, CHRISTIAN KATTERFELD2, SEBASTIAN FUCHS1 & KARL-HEINZ SCHMIDT1 1 Department of Geography, Martin-Luther-University Halle-Wittenberg, D-06099 Halle, Germany
[email protected] 2 Department of Geography, University of Basel, Klingelbergstrasse 27, CH-4056 Basel, Switzerland Abstract The Reintal valley in the Wetterstein Mountains in Upper Bavaria has been dammed by large rockslide deposits in some localities. Behind one of the dams a small lake, the Vordere Blaue Gumpe, was still in existence until 23 August 2005. The lake was a natural sediment sink, decoupling an area of about 1.6 km2 from fluvial sediment export out of the sediment cascade of the Reintal valley. The bergsturz event occurred about 200 years ago. It was dated by evaluating historical maps, paintings, photographs and sketches. Present research is focused on multi-temporal changes of the alluvial deposits of the delta by analysis of aerial photos and geodetic surveying. Volume loss of the lake is closely related to bed load input during extreme events and shows the geomorphic coupling of hillslope and channel systems. From regression analyses of the annual volumetric change of the lake volume, the life-expectancy of the lake was estimated to be about 15 years, before an extreme high magnitude event in August 2005 filled the lake completely with sediment. Now, after the filling of the lake, with the coupling of the catchment area of the Vordere Blaue Gumpe to downstream fluvial sediment export, higher solid load transport is expected in the lower reaches with possible negative effects on infrastructure.