Assessing Torrential Endangered Areas in Bavaria - Consideration of Log Jams at Culverts and Bridges -

Peter DRESSEL, Peter WAGNER and Andreas RIMBOECK

According to the Bavarian Water Act there is an obligation for the water management authorities to determine torrential endangered areas. In a legal sense these areas are primarily potential flood areas however under consideration of typical torrential characteristics. Especially the involvement of solids has to be regarded. In order to enable a systematic and transparent determination of the design event, a standardized modular approach to assess torrential hazards was developed at the Bavarian Environment Agency. In the approach bedload and woody debris are being considered as two separate components. Bedload is considered as a surcharge added to the design hydrograph (100-year discharge). Problems resulting from woody debris in relevant zones (areas of spatial planning) are individually evaluated during hazard assessment. A method which quantifies the potentially accumulating woody debris in the torrent catchment area was developed for this purpose. On this basis, the dangers for log jams at the particular structures are categorized. Subsequently hydraulic calculation is done with a 2D hydraulic model.

2018/1 199-207