Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2000
Publication Date: N/A
Technical Abstract: The formation and upstream migration of headcuts in upland concentrated flows can significantly increase soil losses and sediment yields from agricultural landscapes. Herein we examine the effect of soil microtopography on the growth and development of headcuts typical of rills, crop furrows, and ephemeral gullies. In a laboratory channel, packed sandy clay loam soil beds with pre-formed headcuts 5 to 50 mm high were subjected to simulated rain of about 21 mm/ha for 4 h, followed by an overland flow of about 70 1/min. During overland flow, soil erosion occurred exclusively at the headcut where a scour hole developed, enlarged, and migrated upstream. A steady-state condition ensured: headcut migration rate, scour hole geometry, and sediment yield remained invariant with time. Large initial headcuts can reach steady-state erosion conditions faster in time and shorter in distance as compared to small initial headcuts. For a given bed slope and overland flow discharge, larger initial steps caused deeper headcut to form, but their rates of migration and their scour lengths did not change significantly. In addition, larger initial steps caused an increase in total sediment production and a steepening of the bed slope downstream of the migrating headcut.