Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/25/2001
Publication Date: 3/27/2001
Citation: Temple, D.M., Dabney, S.M. 2001. Hydraulic performance testing of stiff grass hedges. In: Proceedings of the 7th Federal Interagency Sedimentation Conference, March 25-29, 2001, Reno, Nevada. pp. XI-118-XI-124. Interpretive Summary: Stiff grass hedges are used to reduce erosion and to prevent sediment from entering the stream channel system. These hedges are composed of rows of stiff-stemmed grasses planted perpendicular to the direction of flow. The grass rows form a porous barrier to the flow, resulting in sediment deposition upstream of the hedge. To be effective, these hedges must be placed such that they may function without being overtopped and damaged during the flow event. Tests were conducted to determine the quantity of water that could pass through the hedge without damage, and the depth to which the water would be ponded upstream of the hedge. This information will assist in the determination of the most effective placement of hedges for sediment control for specific field conditions.
Technical Abstract: Although stiff grass hedges are being used as vegetative barriers to concentrated flow for the purpose of decreasing erosion and encouraging sediment deposition, the data describing their hydraulic behavior have been limited. Sixteen hedges were tested with discharges being increased incrementally until the hedges failed through local overtopping. Following testing, half of the hedges were cut to remove the damaged stems, while th remainder were allowed to recover without disturbance. Preliminary data analyses and qualitative observation of the behavior of the tested hedges are reported. Test observations included: 1) the interior rows of the three and four-row hedges suffered from lack of light, making the additional rows less effective, 2) the amount of vegetal debris in the flow approaching the hedge had a significant impact on the head loss through the hedge at a given discharge, 3) the head loss through the hedge (depth of water ponded) )was the dominant factor in determining the point of hydraulic failure (overtopping) of the hedge, 4) the switchgrass tended to perform better overall for the conditions tested and remained erect with water ponded to a depth of approximately 1.5 ft, and 5) removing the damaged stems by mowing following testing resulted in more rapid recovery of the hedge.