Author(s): Eddy J. Langendoen; Natasha Pollen; Andrew Simon
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Keywords: Streambank stability; Riparian vegetation; Computer model
Abstract: Riparian vegetation reduces the risk of streambank failure by increasing bank shear strength. First, soil tensile stresses are transferred to the root system thereby reinforcing the streambank material. Second, canopy interception of rainfall and transpiration increases soil suction, increasing resistance to shearing. Vegetative stream restoration measures are commonly designed using an estimated contribution of vegetation to shear resistance. Root biomass and soil water content depend, among others, on plant specie, soil texture, availability of nutrients, and climate. These factors may vary greatly both spatially and temporally. It is therefore difficult to predict if vegetative restoration designs will successfully stabilize streambanks. This paper presents ongoing research to enhance the streambank erosion submodel of the one-dimensional channel evolution model CONCEPTS. Components of the riparian ecosystem management model REMM that simulate the water balance and plant growth in a riparian buffer have been adjusted to more accurately simulate the distributions of pore-water pressure and root biomass. These components have been integrated into CONCEPTS to study the effectiveness of hypothetical woody and herbaceous riparian buffers in controlling streambank stability of an incised stream in Mississippi. Model results showed that spatial and temporal variations in pore-water pressures can be accurately simulated, but may significantly depend on simulated transpiration and rooting depths. Further, the coarse roots of woody vegetation greatly enhance streambank stability and therefore reduce streambank erosion. The fine roots of the herbaceous species have a negligible effect on the stability of the bank of an incised stream if bank height is significantly larger than rooting depth.
Year: 2007