ABSTRACT
ABSTRACT: Recent flood events in Switzerland highlighted that driftwood related problems are not limited to forested mountain regions, as driftwood may reach densely populated areas under high flood discharges. Compared to mountain torrents, the damage potential may increase significantly once driftwood reaches pre-alpine rivers and larger cities. Numerous river crossing structures like bridges and weirs are prone to driftwood blocking so that the resulting backwater rise may overtop the flood levees. Prevalent retention structure as nets or racks spanned across the river are often no solution for larger rivers, because of the excessive structural loading or as the bed-load transport is prevented. Further, the driftwood potential of large catchment areas is difficult to establish and common empirical formulas for mountain torrents are not applicable to lowland rivers. Future risk analysis and engineering measures must therefore be adapted to the challenges of pre-alpine rivers. The present work summarizes techniques to predict the driftwood potential and shows two examples of driftwood retention schemes, optimized with physical scale model experiments.
