Performance of Grass Spillway Linings

For a number of years, the USDA's, Soil Conservation Service and Agricultural Research Service have been collecting data from flows in vegetated earth spillways on flood control reservoirs. The performance of grass spillway linings and the ability of hydraulic attack parameters to predict their failure under various conditions are evaluated for these data. The grass linings are seen to generally perform well when adequate rooting depth is available and the spillway is free from initial discontinuities in the surface and cover. Examination of the data suggests, however, that linings having major discontinuities or available rooting depths less than approximately one foot are likely to experience failure at hydraulic stresses typical of spillway flows. For adequately rooted uniform grass linings, the integral of boundary stress over the time of flow appears to provide a reasonable prediction of lining performance.