Physical modeling of deflector arms in a river table

Abstract

Abstract from thesis: Stream deflectors are a restoration structure used to control bed and bank erosion and improve stream habitat, biodiversity, and aesthetics, yet little research has been conducted on stream deflector design. In this study different deflector designs were modeled using scaled wood geometries in a laboratory river table representing a restored stream. The model deflector arms were designed to represent the agency guidance for length and angle of rock deflector vanes. Vanes were given holes to replicate boulder gaps and key lengths to replicate boulder blocks common to rock vanes. A rapid assessment tool was used to evaluate the performance of each model deflector design, with failure of the vane defined by erosion rates of the river bank and bed. Patterns of failure varied mostly with respect to key size. Bed erosion such as head cuts did not vary on average with respect to key size. Bank erosion at the structure increased in models with shorter keys. The experiment determined longer key length with smaller or no holes had the least erosion. Future experiments should test vane sensitivity to a greater range of river table flow rates and river table sand sizes. This work increased our understanding of how stream restoration deflector structures affect their scour functions.