TY - CHAP
T1 - Towards a dynamic model of gully growth.
AU - Kemp, A. C.
AU - Wallings, D. E.
AU - Yair, A.
AU - Berkowicz, S.
PY - 1990
Y1 - 1990
N2 - Headward migration of gullies around the margins of drainage networks may be a major factor in the increased sediment yields observed in semi-arid southeast Spain. Although many processes have been cited, the precise nature of this gully extension and bifurcation is not known. A gully which is migrating into a hillslope may be considered by way of its morphological dynamics. A digital model has been formulated in which the governing process is erosion by overland flow. Using finite techniques, the continuous phenomena may be approximated by discrete functions. The model grid is set up by defining strip catchments which are bounded by orthogonal flowlines. Overland flow is then routed downslope kinematically, assuming gravity and friction as the controlling forces. Sediment detachment, transport, and deposition were estimated using a Musgrave-type approach which incorporates an interaction term. This compares energy required to carry sediment already in transport with the total capacity of the flow to do work. The consequent change in the slope surface is expressed by migration of the contours along the flowlines. In this manner, the effects of hillslope and gully geometry on gully development may be explored. The simulations indicate a critical balance between a linear propagation of the erosion headwards, and a diffusion laterally of this impulse. Within this balance is identified a possible mechanism for the bifurcation phenomenon. These results are being verified by laboratory experimentation. (A)
AB - Headward migration of gullies around the margins of drainage networks may be a major factor in the increased sediment yields observed in semi-arid southeast Spain. Although many processes have been cited, the precise nature of this gully extension and bifurcation is not known. A gully which is migrating into a hillslope may be considered by way of its morphological dynamics. A digital model has been formulated in which the governing process is erosion by overland flow. Using finite techniques, the continuous phenomena may be approximated by discrete functions. The model grid is set up by defining strip catchments which are bounded by orthogonal flowlines. Overland flow is then routed downslope kinematically, assuming gravity and friction as the controlling forces. Sediment detachment, transport, and deposition were estimated using a Musgrave-type approach which incorporates an interaction term. This compares energy required to carry sediment already in transport with the total capacity of the flow to do work. The consequent change in the slope surface is expressed by migration of the contours along the flowlines. In this manner, the effects of hillslope and gully geometry on gully development may be explored. The simulations indicate a critical balance between a linear propagation of the erosion headwards, and a diffusion laterally of this impulse. Within this balance is identified a possible mechanism for the bifurcation phenomenon. These results are being verified by laboratory experimentation. (A)
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AN - SCOPUS:85041141192
SN - 094757137X
SN - 9780947571375
BT - Unknown Host Publication Title
PB - Wallingford, U.K., International Association of
ER -