Investigating Channel Response to a Dambreak Flood Event in an Alpine River—Downstream Trends in Stream Power and Channel Bed Particle Characteristics

Fieldwork within the framework of SEDAG (SEDiment cascades in Alpine Geosystems) has focused on hydrology, fluvial sediment transport dynamics, and hydrogeomorphological characteristics of the alpine river Partnach (Reintal Valley, Bavarian Alps, Germany). In August 2005 a dambreak flood occurred in the Reintal Valley. The contributing catchment area supplying material for bed load transport at the outlet of the catchment has been enlarged by more than 33% (4.3 km2 + 1.6 km2) due to lake infilling, and thus, reconnecting formerly disconnected parts of the catchment. Post-dambreak downstream variation of total and specific stream power, bed shear stress, and particle characteristics (size and shape) were determined and compared with pre-dambreak findings. As to our knowledge, results of pre- and post-dambreak fluvial-geomorphic investigations have not been published so far for an individual river. Results show high values for total and specific stream power in the post-dambreak regime. In addition, general trends for downstream decreasing in particle size, stream power, and bed shear stress show a degree of regularity after disturbance. Nevertheless, further adjustments of the Partnach channel system in response to the dambreak event are expected in the near future.