The influence of slope angle on final infiltration rate for interrill conditions

Despite numerous studies, the relationship between slope angle and infiltration rate remains unclear. Under different experimental conditions, new processes may be introduced which influence the relationship. The presence of rills, for example, may significantly affect the relationship between slope angle and infiltration rate, so distinct relationships may exist for rill and interrill areas. The objective of this study was to investigate the influence of slope angle on infiltration rate for an interrill area with a surface crust. The experiment was carried out in a laboratory using simulated rainfall and soil trays designed to Limit the processes to those found in interrill areas. Slope angles ranged from 1.5 degrees to 21.5 degrees: infiltration was calculated from the overland flow rate, and microtensiometers and micromorphological analysis were used to characterise the seals. Infiltration rate decreased with increasing slope angle; image analysis of pore characteristics in the affected layer and subseal pressure head measurements indicated there were no differences in seal characteristics between slope angles. The results showed that sealing intensity did not vary with slope angle, and the dominant influence of slope angle on infiltration rate resulted from changes in overland flow depth and surface storage. The results also suggest that small changes in seal hydraulic conductivity with microrelief play an important role in the infiltration process. (C) 1997 Elsevier Science B.V.