Calibration of a hydrological model using sediment proxy data

Abstract

Soil loss and sediment transport in Mediterranean areas are highly-complex and non-linear processes which have been only partially understood. In order to facilitate the comprehension of these phenomena, distributed models can be very helpful tools for sediment yield estimation. In this work, a modelling approach is proposed to reproduce and evaluate erosion and sediment yield processes in a Mediterranean catchment (Rambla del Poyo, Valencia, Spain). Due to the lack of sediment production records for model calibration and validation, a detailed description of the alluvial stratigraphy infilling a check dam that drains a 12.9 km2 sub-catchment was used as an indirect evidence of sediment yield data. These dam infill sediments showed evidences of at least 15 depositional events (floods) over the time period 1990 ¿ 2009, with a total estimated volume ranging between 1250 and 1435 m3, depending on the calculation approach. The TETIS-SED model, a distributed conceptual hydrological and sediment model, was coupled to the Sediment Trap Efficiency for Small Ponds (STEP) model for reproducing reservoir retention, and it was calibrated and validated using the sedimentation volume estimated for the depositional units associated with discrete runoff events. The results show relatively low net erosion rates compared to other Mediterranean catchment (14 t km-2 y-1), probably due to the prevalence of limestone and homogeneous vegetation cover, and confirms the ephemeral behaviour of the stream. The modelled sediment production rates offer satisfactory results, further supported by palaeohydrological evidences, showing its great potential for the quantitative analysis of sediment dynamics in ungauged Mediterranean basins.