Sediment transport in a high mountain catchment in the central Spanish Pyrenees

Abstract

This paper reports on sediment transport rates from a 0.33 km 2 high mountain catchment in the central Spanish Pyrenees. Sediment transport from three distinct periods are compared: winter, when discharge is very low and regular; the spring snowmelt season, when discharge is high during several weeks, with daily oscillations; and the rest of the year when discharge is controlled by fluctuations in the precipitation regime. It is shown that sediment transport is dominated by the summer and autumn storm events, with the storms of October 1987 accounting for 61% of the bedload transport in seven years. In addition the sediment transport is considered in three components: solutes, suspended sediment load and bedload. In years with a normal pluviometric regime, the ratio between the three modes of sediment transport is between 82 and 94 percent solutes, 5 to 7.5 percent suspended sediments and 1 to 10 per cent bedload. This too varies greatly from year to year, with the October 1987 storms transporting 17 tons of bedload transport whilst the dissolved and suspended load only reached 2,000 and 750 kg respectively.