Local and supralocal effects of central and decentralized measures of flood protection

摘要

The importance of natural measures of retention in the valleys and the effects of these measures on flood protection is a matter of official discussion. But there are no reliable studies as to which effects these measures, when carried out on smaller tributaries, have on the flood discharge of the main rivers. Exemplary for the Nahe-basin (4065 km~2), a catchment of the low mountain range, the effect of decentralized natural measures of retention in comparison with central detention reservoirs on the flood discharge were calculated. For that purpose a conceptual river basin model was used. In the model the natural measures of retention were simulated by revitalization measures and various small detention reservoirs in the valleys. The flood peak reduction achieved by the natural measures of retention in the catchment of the Nahe river is 8,2 percent at the mouth of the Nahe river. Central detention reservoirs with the same volume only lead to greater peak reduction if they are built at the main river. Concerning the supralocal effects of decentralized measures of retention was determined that measures which are employed at the tributaries of the upper catchment will lead to the greatest flood peak reduction downstream the main river.