Modelling the long-term sediment trap efficiency of small ponds

A numerical model (sediment trap efficiency for small ponds-STEP) is develo ped to simulate sediment deposition in small ponds (i.e. < 1 ha) and to cal culate the sediment trap efficiency (STE). The algorithms are kept simple t o allow the model to simulate larger time periods (i.e. several years). Eig ht runs with an experimental pond were executed to test the model. The STEP model produces reasonable predictions of STE as well as the shape and magn itude of the effluent sediment concentration graph. The model efficiency of STEP for the prediction of STE equals 0.38 and the root mean square error equals 4.7%. Similar models, such as DEPOSITS and CSTRS, were inefficient i n predicting the experimental results. The STEP model was used to simulate the long-term (33 years) STE of small retention ponds in central Belgium us ing 10-min rainfall data. For a typical pond (1000 m(-2)) with a catchment area of 25 ha, annual STE can vary from 58 to 100%, with a long-term STE of only 68%. Copyright (C) 2001 John Wiley & Sons, Ltd.