Ž . Catena 46 2001 103–123 www.elsevier.comrlocatercatena Soil erosion under different rainfall intensities, surface roughness, and soil water regimes M.J.M. Romkens a, ) , K. Helming b , S.N. Prasad c ¨ a USDA-ARS National Sedimentation Laboratory, PO Box 1157, Oxford, MS 38655, USA b Department of Soil Landscape Research, ZALF, Muencheberg, Germany ¨ c UniÕersity of Mississippi, UniÕersity, MS 38677, USA Abstract Soil erosion is a complex phenomenon involving the detachment and transport of soil particles, storage and runoff of rainwater, and infiltration. The relative magnitude and importance of these processes depends on a host of factors, including climate, soil, topography, cropping and land management practices, control practices, the antecedent conditions, and the size of the area under consideration. In this study, the results of a series of experiments are reported, summarizing the soil loss and runoff response from a 0.6 =3.75 m area to different rainstorm regimes, slope steepnesses, subsurface soil water pressures, and surface roughnesses under controlled laboratory conditions using a flume and rainfall simulator as water applicators, and a laser microreliefmeter and tensiometric system as soil response measuring devices. The soil chosen was a highly erodible Ž . Ž. Grenada loess fine silty, mixed, thermic, Glossic Fragiudalf . The results showed: 1 a sequence of rainstorms of decreasing intensity on an initially air-dry smooth surface caused more soil loss Ž. than a sequence of similar storms of increasing intensity; 2 the surface roughness–sediment Ž. concentration relationship was not monotonic in nature; 3 subsurface soil water pressure substantially affected sediment concentration in runoff but only marginally impacted runoff Ž. amounts; 4 initially smooth, uniform surfaces may yield less soil loss than initially rough Ž. surfaces; 5 interrill runoff occurred as spatially varying flow in which flow patterns determine the locations of rills. Published by Elsevier Science B.V. Keywords: Erosion processes; Sediment concentration; Drainage networks; Surface microrelief; Roughness; Seepage; Soil water pressure 1. Introduction Soil erosion is a complex and multifaceted process which involves a host of factors and conditions with combinations, variations, and interactions that substantially affect ) Corresponding author. Tel.: q 1-662-232-2901; fax: q 1-662-232-2915. Ž . E-mail address: romkens@sedlab.olemiss.edu M.J.M. Romkens . ¨ 0341-8162r01r$ - see front matter. Published by Elsevier Science B.V. Ž . PII: S0341-8162 01 00161-8