Charakteristika des Sedimenttransports in einem Kleineinzugsgebiet der Aragonesischen Pyrenäen

Abstract

Characteristics of sediment transport in a small catchment in the Spanish Pyrenees. The transport of suspended sediment during a stormflow event is very variable. The resulting hysteretic loop of the relationship of the discharge and suspended sediment concentration is used in the present paper to classificate rainfall-runoff-events and identify by canonical discriminant analysis the factors determining the different event types. The analysis of 19 events in a headwater catchment of the Central Pyrenees leads to the identification of 3 types of floods. A majoritary with clockwise shaped hysteretic loop, a second one with anti-clockwise shaped hysteretic loop and a third group with eight shaped hysteretic loop. The most important factor for generating different types of events is the soil moisture in the catchment. On a secondary level, total rainfall amount and precipitation of the 3 days before are important. So, the different flood types are generated with different contributing areas or by different processes. Clockwise shaped events have limited sources of suspended sediment near the channel with limited supply. Anti clockwise shaped events lead sediments from all over the catchment to the ravine. Eight-shaped events are produced under dry conditions, when rainfall intensity exceeds infiltration capacity, so sediments sources may be localised all over the catchment, but their conection to the fluvial network is stoped rapidly with decreasing precipitation.