SOIL PROPERTY PATTERNS AND TOPOGRAPHIC PARAMETERS ASSOCIATED WITH EPHEMERAL GULLY EROSION

The pattern of ephemeral gully erosion and associated soil properties were investigated in three southeastern Minnesota soilscapes during 19 88 and 1989. The associations between topographic attributes and erosi on characteristics of sample sites were also examined. No ephemeral er osion was measured after the investigation began in the drought year o f 1988. In 1989 soil lost from ephemeral gullies ranged from 0.8 to 1. 6 Mg/ha (.4 to .7 ton/ac) at the study sites, or one-tenth of that rep orted in the literature for similar watersheds. Pre-1988 data availabl e at one site showed that soil voidage was an order of magnitude great er during the wetter-than-normal 1986 season. A simple erosion model p redicting topsoil removal and subsoil mixing in upper reaches and depo sition in lower ephemeral gully reaches, does not accurately describe erosion processes in these landscapes. Impact of ephemeral erosion on soil properties in landscapes varied depending on relative 1) rill and interrill contributions, 2) proclivity for channel drifting, and 3) o ccurrence of depositional sorting in channels. Topographically sensiti ve controls of ephemeral erosion, such as surface saturation and strea m transport capacity; played different roles in channel formation at e ach site. Topographic indices most useful for predicting ephemeral ero sion were planform curvature, profile curvature.slope, Ln (unit area/s lope), unit area.slope, and planform curvature.upstream contributing a rea.slope.