Differences in hillslope runoff and sediment transport rates within two semi-arid catchments in southeast Spain

Abstract

This paper focuses on hillslope runoff and sediment transport within two catchments in southeast Spain. Five monitoring sites were established on hillslope concavities throughout the two catchments. The techniques used were mini-crest stage recorders, spray-painted lines, sediment traps and tipping bucket rain gauges (established during previous research). Results show that a storm event in the Rambla Nogalte on 30 June 2002 of 83.0 mm was responsible for a maximum runoff depth of 12 cm and a maximum hillslope sediment transport of 1886 cm 3 m −1. The same storm in the Rambla de Torrealvilla produced 53.4 mm of rainfall on the 1 July 2002, had a maximum runoff depth of 26 cm and resulted in 2311 cm 3 m −1 of sediment transport. There is evidence to suggest that measured sediment transport is related to runoff and a qualitative estimate of Morphological Runoff Zones (MRZ). Sediment transport and depth of runoff varied dramatically with lithology; marl sites produced most runoff and sediment transport, followed by the sites of mixed red and blue schist, then blue schist. These results are important for understanding the behaviour of slopes and show that for short lived storms with high, but not rare, rainfall intensities and total rainfall amounts, runoff can cause significant hillslope sediment transport in semi-arid areas.