The role of rock properties in the development of bedrock-incised rills and gullies: Examples from Southern Africa |
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| Authors: | George F Dardis Dr Heinrich R Beckedahl |
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| Institution: | (1) Sedimentology and Palaeobiology Laboratory, AHEC, East Road, CB1 1PT Cambridge, UK;(2) Department of Geography, University of Transkei, Private Bag X1, Unitra, Umtata, Transkei, Southern Africa |
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| Abstract: | Physical properties (Schmidt hammer in situ rock strength; degree of weathering; orientation, spacing, width and continuity of joints, bedding planes and faults; groundwater flow) of bedrock-incised rills and gullies were ecamined at selected localities in southern Africa. The resulting data was compared to froms of erosion observed in the field to test for possible influences of rock physical properties on rill and gully development. Bedrock-incised rill erosion occurs at low RMS (Rock Mass Strength) values (40–50). Rills generally do not form where RMS values are high (> 50). Though V-shaped bedrock-incised gullies form in lithologies with a wide range of RMS values (40–69), these values exert strong control on longitudinal morphometry. Future studies should concentrate on establishing a database on properties of erosion forms to aid identification of lithological conditions (e. g. deep regolith) which are potentially susceptible to accelerated erosion. |
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