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Field and laboratory determination of water-surface elevation and velocity using noncontact measurements

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Abstract

Noncontact methods for measuring water-surface elevation and velocity in laboratory flumes and rivers are presented with examples. Water-surface elevations are measured using an array of acoustic transducers in the laboratory and using laser scanning in field situations. Water-surface velocities are based on using particle image velocimetry or other machine vision techniques on infrared video of the water surface. Using spatial and temporal averaging, results from these methods provide information that can be used to develop estimates of discharge for flows over known bathymetry. Making such estimates requires relating water-surface velocities to vertically averaged velocities; the methods here use standard relations. To examine where these relations break down, laboratory data for flows over simple bumps of three amplitudes are evaluated. As anticipated, discharges determined from surface information can have large errors where nonhydrostatic effects are large. In addition to investigating and characterizing this potential error in estimating discharge, a simple method for correction of the issue is presented. With a simple correction based on bed gradient along the flow direction, remotely sensed estimates of discharge appear to be viable.

Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Field and laboratory determination of water-surface elevation and velocity using noncontact measurements
Year Published 2016
Language English
Publisher International Association of Hydraulic Research
Contributing office(s) National Research Program - Central Branch
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Proceedings of the 20th Congress of the Asia Pacific Division of the International Association for Hydro Environment Engineering & Research
Conference Title 20th Congress of the Asia Pacific Division of the International Association for Hydro Environment Engineering & Research
Conference Location Colombo, Sri Lanka
Conference Date August 28-31, 2016