RESUSPENSION OF FINE SEDIMENT IN RESERVOIRS - A CASE STUDY OF THE LOWER INN RIVER

1 THE LOWhR unR INNThe Inn river has its source in the alPine region of the GraubUnden canton of Switzerand. ThecatChment area of about 260(X} kIn2 includes mountains of the central Alpes up to 40(X) m. The river runs5l7 km thrOugh the countries of SwitZerand, Austria and Germany on itS way into the Danube mver. Thedischarge of the river at its mouth in the city of Passau is mainly infiuenced by the snow melt in themountainous catchment area and vches between apProx. 200 m3ls durin…

RESUSPENSION OF FINE SEDIMENT IN RESERVOIRS A CASE STUDY OF THE LOWER INN RIVER

The Inn river, major tributary of the Danube river in Germany, has its origin in the higher alpine region of Switzerland and Austria. Mainly for flood management reasons and the extensive production of hydropower based electricity it was fixed with massive embankments and subdivided into a chain of reservoirs. Caused by severe amounts of sediments, mostly fine material as suspended load, a significant sedimentation of the reservoirs takes place. Different strategies are known and investigated to extend the life-cycle of the reservoirs and the efficient use of the turbines. During the past decades parts of the reservoirs turned into ecologically valuable habitats which had to be excluded from e.g. flushing operations and are protected areas nowadays. In the meantime ecologists had to realize that the value of those ecosystems is declining as the result of further aggradation of the depositions leading to a new but static condition. Measures are discussed to stimulate dynamic changes of the sand bars avoiding their stabilization by vegetation like bushes and trees. Basic ideas of the concept and the 2d-model to simulate and optimize engineering solutions are described respecting ecological restrictions.