Comparative application of two erosion models to a basin

Abstract

Two mathematical models were used to estimate the annual sediment yield resulting from rainfall and runoff at the outlet of the Nestos River basin (Toxotes, Thrace, Greece). The models were applied to that part of the Nestos River basin (838 km") which lies downstream of three dams. Both models consist of three submodels: a simplified rainfall-runoff submodel, a physically-based surface erosion submodel and a sediment transport submodel for streams. The two models differ only in the surface erosion submodel: that of the first model is based on the relationships of Poesen (1985) for splash detachment and splash transport, while the corresponding submodel of the second model is based on the relationships of Schmidt (1992) for the momentum flux exerted by the droplets and the momentum flux exerted by the overland flow. The degree of conformity between the annual values of sediment yield at the basin outlet according to both models is satisfactory.

Estimate of Continuous Sediment Graphs in a Basin, Using a Composite Mathematical Model

“…In previous publications of the second author, different versions of the present model were used (Hrissanthou 2002(Hrissanthou , 2005. The main differences between the previous model versions and the present model version are summarized below: (a) The time variation of stream discharge and sediment discharge, on a hourly time basis, at the basin outlet is computed in the present model version.…”

“…In the previous studies, sediment yield values at the basin outlet were not available. (e) The previous model versions were applied to Nestos River basin, downstream of Platanovrysi Dam, with an area of 838 km 2 (Hrissanthou 2002) and to Kompsatos River basin with an area of 567 km 2 (Hrissanthou 2005). Both basins are neighbouring to Kosynthos River basin, with an area of 237 km 2 , considered in the present study.…”

“…After trial computations, r e was taken as equal to 0.7. However, the above manner of r e determination has as a consequence that this parameter loses its physical meaning in relation to soil cohesion and becomes rather an arithmetic calibration factor (Hrissanthou 2002). Table 5 displays the soil slope gradient and the soil cover factor values, for each subbasin.…”

“…However, the correlation of the influencing parameters of the rainfall erosion is enabled in an empirical way (Hrissanthou 2002).…”

“…For the estimate of soil erosion due to rainfall in a sub-basin, the following basic equations of Poesen (1985) are used: The soil cover factor C is not included in the original relationship of Poesen for splash detachment, because this relationship is valid for bare soils. In order to take into account the decrease of splash detachment because of the vegetation, the dimensionless vegetation factor C of the USLE is considered as appropriate to express the vegetation influence (Hrissanthou 2002).…”