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Title: SCOUR BELOW AN OVERFALL (ADD ACCEPT. DATE)

Author
item Robinson, Kerry
item Hanson, Gregory
item Cook, Kevin

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: 7/14/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: As flowing water falls over a headcut or overfall, a scour hole can form just downstream. This scour hole causes the overfall height to increase and can cause the overfall to become unstable. This research was done to determine how fast a gully moves as the headcut becomes unstable. Measurements were made to determine how quickly the scour hole deepened for rdifferent soil conditions. The soil density was found to be a good indicator of the rate of scour. The overfall height did not have a strong influence on the rate of scour. These results should be of value to those engineers and researchers interested in soil erosion, headcut advance, and scour below hydraulic structures.

Technical Abstract: Scour below an overfall contributes to headcut instability and gully advance. Eight tests were conducted to measure the rate of vertical scour downstream of a gully overfall or headcut. All tests were performed with a low tailwater level to insure the worst case scour condition. The manner in which the cohesive soil was placed and compacted influenced the rate of scour. The scour rate was observed to increase as the soil density decreased. Vertical scour rates were observed from 0.00011 to 0.033 m/min. Over the range of overfall heights examined, the linear scour rate was not strongly influenced by overfall height.