Hochwasserrückhalt durch natürliche Hochwasserretention entlang der bayerischen Donau

Natural flood retention in river basins is a complex topic very much influenced by hydrodynamic processes in the flooded areas. Before the first anthropogenic corrections in the early 19^th century, the Bavarian Danube was a braided river not significantly influenced by human civilization or activities. With two-dimensional simulations using a historical digital terrain model of this time it was shown, that despite the immense retention volume in the historical meadows the flood peaks would not have been significantly reduced compared to the nowadays and heavily channelized, man-made modified situation. This present paper compares the present and historical states of the Danube River basin for the very interesting and hydro-dynamically complex river stretch from Neu-Ulm to Donauwörth. For the comparison a systematic study considering synthetic hydrographs of different width, neglecting the inflows of the intermediate catchment, is performed. The effect of flood retention is quantified by the damping and detention of the flood peaks. The results show clearly that flood retention cannot be correlated with the amount of activated retention volume.