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Title: INFLUENCE OF BACKWATER ON HEADCUT ADVANCE

Author
item Robinson, Kerry
item Hanson, Gregory

Submitted to: Proceedings ASCE North American Water and Environment Congress
Publication Type: Proceedings
Publication Acceptance Date: 6/22/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The formation and movement of a gully headcut is a dominant form of damage to earth spillways and other improved channels. The erosion processes that cause gully growth are, at best, poorly understood. Research was conducted to learn more about headcut erosion and to develop the tools necessary to predict headcut advance. The backwater level downstream of a gully headcut was found to have a significant influence on the rate of headcut movement. For the soil tested, the headcut advance rate was observed to increase over sevenfold simply by changing the downstream backwater level. The maximum headcut advance rate was found to occur at intermediate backwater levels. This information should be of value to researchers and practicing engineers with responsibilities for maintaining spillways and stable channels.

Technical Abstract: A study was performed to examine the influence of backwater level downstream of an overfall on headcut advance rate. The discharge, overfall height, and soil type were held constant while varying tailwater level. The intermediate tailwater levels with a backwater to overfall height ratio of approximately 0.8 produced the largest advance rates. The tailwater level downstream of the overfall was observed to vary the advance rate by a factor of 2.6 to 7.5 over the range of soil conditions tested. This study suggests that an accurate prediction of headcut advance must incorporate accurate backwater information.