THE INFLUENCE OF SLOPE ANGLE ON FINAL INFILTRATION-RATE FOR INTERRILLCONDITIONS

Despite numerous studies, the relationship between slope angle and inf iltration rate remains unclear. Under different experimental condition s, new processes may be introduced which influence the relationship. T he presence of rills, for example, may significantly affect the relati onship between slope angle and infiltration rate, so distinct relation ships may exist for rill and interrill areas. The objective of this st udy was to investigate the influence of slope angle on infiltration ra te for an interrill area with a surface crust. The experiment was carr ied out in a laboratory using simulated rainfall and soil trays design ed to Limit the processes to those found in interrill areas. Slope ang les ranged from 1.5 degrees to 21.5 degrees: infiltration was calculat ed from the overland flow rate, and microtensiometers and micromorphol ogical analysis were used to characterise the seals. Infiltration rate decreased with increasing slope angle; image analysis of pore charact eristics in the affected layer and subseal pressure head measurements indicated there were no differences in seal characteristics between sl ope angles. The results showed that sealing intensity did not vary wit h slope angle, and the dominant influence of slope angle on infiltrati on rate resulted from changes in overland flow depth and surface stora ge. The results also suggest that small changes in seal hydraulic cond uctivity with microrelief play an important role in the infiltration p rocess. (C) 1997 Elsevier Science B.V.