An inquiry set up in central Belgium shows that 43% of the municipalities (n = 121) suffer every 2-5 years from muddy floods generated from direct runoff from agricultural land and 36 % with flooding of permanent streams. In order to control floods, more than 100 retention ponds have been constructed over the last 20 years with 50 more due to be built in the near future. These retention ponds store large volumes of sediment from runoff events and are thus dredged regularly resulting in annual costs of the order of 1.5 million ECU. These sediment volumes can be used for assessing and predicting sediment yield values for drainage basins. Values for sediment yield vary between 0.19 and 9.32 m3 ha"1 year"1 for drainage basins ranging from 25 to 5000 ha.