Runoff and sediment transport in a degraded area

Abstract

aBStRaCtgully erosion occurs by the combined action of splash, sheetwash and rillwash (interrill and rill erosion). these erosion processes have a great capacity for both sediment production and sediment transport. the objectives of this experiment were to evaluate hydrological and sediment transport in a degraded area, severely dissected by gullies; to assess the hydraulic flow characteristics and their aggregate transport capacity; and to measure the initial splash erosion rate. in the study area in guarapuava, State of paraná, Brazil (lat 25° 24' S; long 51°24' W; 1034 m asl), the soil was classified as Cambissolo Húmico alumínico, with the following particle-size composition: sand 0.116 kg kg -1 ; silt 0.180 kg kg -1 ; and clay 0.704 kg kg -1 . the approach of this research was based on microcatchments formed in the ground, to study the hydrological response and sediment transport. a total of eight rill systems were simulated with dry and wet soil. an average rainfall of 33.7 ± 4.0 mm was produced for 35 to 54 min by a rainfall simulator. the equipment was installed, and a trough was placed at the end of the rill to collect sediments and water. during the simulation, the following variables were measured: time to runoff, time to ponding, time of recession, flow velocity, depth, ratio of the initial splash and grain size. the rainsplash of dry topsoil was more than twice as high as under moist conditions ( index terms: field measurement, water erosion, simulated rain, rainsplash, runoff.(1) Received for publication in January 05, 2011 and approved in november 15, 2011. (2)

Rill length and plot‐scale effects on the hydrogeomorphologic response of gravelly roadbeds

“…The average rainfall‐normalized sediment production rate from the unpaved road was only slightly lower (~19%, ns) than road erosion previously measured for unpaved roads at the micro‐plot scale (i.e. ≤0.5 m 2 ) and was slightly higher (15%) than that from an actively used pastureland area degraded by severe sheet wash and a well‐developed rill system (Thomaz, ; Table ). In addition, the unpaved road erosion rates observed by this study are 3 to 17 times higher than slash‐and‐burn agricultural areas in the region (Thomaz, ; Table ).…”