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Noncontact methods for measuring water-surface elevations and velocities in rivers: Implications for depth and discharge extraction

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Abstract

Recently developed optical and videographic methods for measuring water-surface properties in a noninvasive manner hold great promise for extracting river hydraulic and bathymetric information. This paper describes such a technique, concentrating on the method of infrared videog- raphy for measuring surface velocities and both acoustic (laboratory-based) and laser-scanning (field-based) techniques for measuring water-surface elevations. In ideal laboratory situations with simple flows, appropriate spatial and temporal averaging results in accurate water-surface elevations and water-surface velocities. In test cases, this accuracy is sufficient to allow direct inversion of the governing equations of motion to produce estimates of depth and discharge. Unlike other optical techniques for determining local depth that rely on transmissivity of the water column (bathymetric lidar, multi/hyperspectral correlation), this method uses only water-surface information, so even deep and/or turbid flows can be investigated. However, significant errors arise in areas of nonhydrostatic spatial accelerations, such as those associated with flow over bedforms or other relatively steep obstacles. Using laboratory measurements for test cases, the cause of these errors is examined and both a simple semi-empirical method and computational results are presented that can potentially reduce bathymetric inversion errors.

Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Noncontact methods for measuring water-surface elevations and velocities in rivers: Implications for depth and discharge extraction
ISBN 9781138029132
Year Published 2016
Language English
Publisher CRC Press
Contributing office(s) National Research Program - Central Branch
Description 9 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title RiverFlow 2016
First page 637
Last page 645