Measurement of the Free-Surface Elevation for Flows in Complex Topography Using Photogrammetry

Abstract

Predicting the flow in rivers is an important concern regarding potential damages induced by floods. Numerical models, if they can be used as predicting tool, need to be tested to assess their reliability. This can be done by comparing their results to field measurements or experimental data. However, such comparisons are often not easy to interpret since the differences can come from a multitude of causes. Therefore, it is preferred to use well-documented experimental data obtained in a well-controlled environment. As regards water level measurements, several methods exist. Gauges provide information on a small area (point measurement method). Other techniques (imagery-based analysis) such as filming through a side panel provide the water level along the considered axis but require an optical access to the area which is not always possible. This paper investigates the use of photogrammetry to measure the water level. Photogrammetry is a nonintrusive method allowing for the capture of the water level over a large area in one run of the experiment. However, its application still presents numerous challenges. The work presented here compares the results obtained using photogrammetry to other more classical measurement methods in the case of a steady flow in an arbitrary topography built in concrete. The results show good agreement between both measurement techniques and highlight the capabilities of using photogrammetry in the laboratory.