|Casali, J - PUBLIC UNIV OF NAVARRA,SP|
Submitted to: Trans American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: December 15, 1998
Publication Date: N/A
Technical Abstract: Headcuts are nearly vertical step-changes in bed surface elevation where intense, localized erosion takes place. The development and upstream migration of headcuts in unconsolidated, cohesive materials has been linked to such fundamental geomorphic processes as rill and gully erosion, concentration of overland flow, and initiation of drainage systems. Here we present experimental results on the growth, development, and migration of headcuts in concentrated flows typical of upland areas. The experiments utilized a soil bed packed incrementally, simulated rain to develop a stable surface seal, and a pre-formed headcut subjected to overland flow. Our results show that (1) soil erosion during headcut progression on shallow slopes is steady state where headcut geometry, migration rate, and sediment yield remain constant, (2) smaller initial step-heights require a longer time and length scale to reach steady-state than larger steps, (3) similarity of headcut shape and dimension is achieved within each experimental run, over a four-fold increase in flow discharge, and over a ten-fold increase in bed slope, (4) bed adjustment downstream of a migrating headcut is controlled flow transport capacity, and (5) size-density sediment sorting occurs within the self-made bed downstream of the headcut and sediment yield. These unique data will be used to further advance the prediction of soil loss in agricultural areas impacted by headcuts.