Author Description

Bendway weirs are being considered by INDOT as a potential alternative countermeasure for bank erosion at channel bends that might be more environmentally sensitive than the traditional riprap. These are linear structures extending riverwards from the bank to be protected, but unlike the more familiar spur structure, they are intended to be overtopped by the design flow. The flow over the weir crest is supposed to be directed perpendicularly to the plane of the weir, and so by appropriate placement of the weir(s), the flow can be directed away from the bank, thus protecting it. Design guidelines for such structures are available in HEC-23, but these have not received much detailed scrutiny regarding their performance. Also, the HEC-23 design is independent of approach velocity. A laboratory study was conducted to examine the effectiveness of Bendway weirs based on the HEC-23 guidelines in protecting the outer bank of 90° bend, characterized by a single ratio of radius of curvature to top width of 3.3. The laboratory model had both erodible bed and banks. Experiments were conducted with and without weirs, with three different weir crest heights (including one that was essentially not overtopped), and two approach velocities. Measurements of erodible boundary elevations, as well as point velocities, were made. Effectiveness was assessed by comparison with the corresponding no-weir case, and with the initial "artificial" channel geometry.