Design of submerged vane matrices to accompany a river intake in Australia

Abstract

This paper focuses on the design of river-based submerged vane matrices in a regional Australian context. The specific study site is proximal to intake screens within the riverbed that experiences continual clogging from sediment deposition. The local authority experiences discontinuous supply to the water-treatment plant owing to a high sediment concentration. Data on the river flow, depth, turbidity and rainfall were collected, and analyses of sediment composition, gradation and density were carried out within this research. Through the study of incipient sediment motion and hydraulics, with specific reference to the method of Shields, the shear stress and critical velocity necessary for sediment motion were determined. The results provided guidance for an iterative modelling design of submerged vanes within the local context ultimately configured as symmetrical diverging vane matrices. Placed a short distance upstream of the existing intake screens at a 30° angle to the river flow direction on two symmetric arms, the three vane arrays generate secondary flow as a function of the existing flow around the vanes. The purpose of the vane matrix is twofold, firstly to redirect sediment away from the existing infiltration galleries and secondly to scour the riverbed within the bounds of the matrices. With a subsequent increase in the depth of water, intake screen(s) placed within and orthogonal to the flow would benefit from an increased depth in combination with a reduction in sediment delivery to the screen(s).