The Remote Monitoring Of Surface Velocity, Bathymetry And Discharge In Rivers And Open Channel Flows

Abstract

Motivated by the ubiquitous nature of turbulent surface features that are present on the surface of naturally occurring shallow flows, this dissertation leverages information contained within these signatures to remotely monitor bathymetry, bed shear stress and volumetric discharge. A series of Large-Scale Particle Image Velocimetry (LSPIV) and Acoustic Doppler Velocimetry (ADV) experiments are conducted in a wide-open channel for a variety of different bathymetric conditions. A methodology is developed that remotely and accurately determines volumetric flow rate from free surface imagery. This methodology takes advantage of the ubiquitous nature of counter-rotating vortices in wide-open channel flows, which have been demonstrated to scale with the flow and influence the pattern of velocity on the free surface. This approach to remote volumetric discharge monitoring is more efficient and cost-effective than current direct methods of determining volumetric flow rate. It reduces hazards to USGS personnel and yields the same or better accuracy relative to current methods. A second technique is developed that permits remote and large-scale assessment of bed shear stress. This is accomplished through correlation of dissipation measurements on the free surface with dissipation measurements in the upper portion of the water column. In open channel flow the distribution of dissipation in the water column follows a semi-theoretical relation developed by Nezu & Nakagawa (1993), which includes friction velocity. Hence, by understanding the correlation between free surface and near-surface values of dissipation, full depth profiles of dissipation can be approximated and the friction velocity, and subsequently bed shear stress, can be determined. The development of this technique has important implications for the prediction of sediment transport.