Alfred Stach

Abstract

In the first half of June 1988 intense rainfall was recorded in the center of West Pomerania. It caused a flash flood in the catchment of the upper Parsęta which made itself felt also in the lower reaches of the river. The flood occurred in three periods of flood waves (11.1, 2.2 and 6.6 m3s"1 respectively, mean annual discharge equalled 0.7 m3s"1). In the analysis attention is paid to hydrological and geomorphological aspects of the transport of suspended load along the Parsęta course as effects of processes taking place in the catchment area. The transport of the suspended sediment load varied over the flood period because of a strong hysteresis effect. We distinguished three kinds of hysteresis loops: clockwise, anticlockwise and two-part. They represent different conditions of water and sediment supply from the catchment and the Parsęta channel. During the flood period 203 tons of suspended sediment load were removed, compared with 891 tons for the whole year. W^hen comparing water flow and the transport of suspended material recorded at two extreme stations of the longprofile of the Parsęta River, the striking aspect is their dependence on the distance from the agent, i.e. the heavy rainfall in the upper Parsęta catchment, and indirectly on the catchment size. In the case of a small catchment, the responses are more dynamic and diversified, while in a large one they are more stable and even. The results allow an evaluation of the role of an extreme phenomenon in fluvial transport in the lowland and young glacial catchments.

Andrzej Kostrzewski [Andrzej.Kostrzewski@twarda.pan.pl], Institute of Geography and Spatial Organization Polish Academy of Sciences, Twarda 51/55, 00‑818 Warszawa, Poland
Alfred Stach [alfred.stach@amu.edu.pl], Instytut Badań Czwartorzędu, Uniwersytet im. Adama Mickiewicza ul. Fredry 10, 61-701 Poznań
Zbigniew Zwoliński, Institute of Geoecology and Geoinformation Adam Mickiewicz University in Poznań Dzięgielowa 27, 61-680 Poznań: Poland