Wall-Porosity Effects on Sediment Deposition and Scour at a Deflector Wall in an Alluvial Channel

Abstract

Many water intakes and diversions are prone to blockage by drifting material, notably vegetation and ice. A way to avert blockage is by means of a deflector-wall and floating debris boom. However, the wall may be subject to local scour and cause bed sediment to accumulate at the intake or diversion entrance. This paper presents data and observations from live-bed, laboratory flume tests showing that a porous deflector wall reduces scour depth and height of sediment accumulation. The flume tests used deflector walls angled at 9° and 3° to the bank, as well as varying levels of wall porosity. A minimum value deflector-wall porosity of 5–75% is recommended for design. This range ensures minimal scour or accumulation of sediment at the wall and suitable wall performance as a deflector.