Digital terrain modelling of drainage channel erosion

Drainage channels constructed on highly erodible soils in some areas of Sou thern Navarre during 1988 have undergone severe erosion, including bed and bank degradation. This erosion triggered lateral gully development that aff ected adjacent cultivated fields. These processes are similar to those obse rved in permanent gullies in the area. One severely eroded channel represen tative of the area was selected for further examination. The amount of eros ion was determined by comparing the initial size of the drainage channel wi th its present condition using digital terrain models and a terrain represe ntation system. Results show that average soil losses along the eroded reac h are 3.62 m(3)/m, highlighting the necessity of using improved design meth ods. Current simulation models can aid in determining such design criteria. If drainage channels are to be constructed in areas of highly erodible soi ls, they should be shorter and restricted to the lower regions of the water sheds with gentler slopes. Sudden changes in bed slope should be avoided, a nd adequate erosion control techniques within the channel should be conside red. The measurement method used provides detailed information on channel e rosion processes with a reasonable effort. (C) 1999 Silsoe Research Institu te.