Emplois de l’aDcp en rivière : une revue de synthèse

Uses of aDcp in rivers: a review

Cemagref, Unité de Recherche Hydrologie-Hydraulique, 3 bis quai Chauveau CP 220 F-69336 Lyon cedex 09, France

Abstract

For the last fifteen years, acoustic Doppler current profilers (aDcp) have been increasingly used to measure river discharge. Originally designed for oceanographical applications, aDcp can provide vertical profiles of 3D instantaneous flow velocity, referenced in space and time at a sampling rate of up to about 5 Hz. ADcps emit ultrasonic waves whose rated frequency typically ranges from 300 to 3,000 kHz. Water velocity is measured by Doppler effect, so that no local parameter calibration is required. Due to some technical restrictions it is impossible to measure velocity in certain parts of the river cross-section. Uncertainty assessment is made difficult by the complexity of the measurement process and potential errors that stem from field deployment. Consequently practitioners are looking for guidelines and corrective methods in order to assess the quality of discharge measurement, especially in case of moving bottom or complex flows (eddies, recirculating flows, secondary currents, etc.). Besides, today much experimental effort is dedicated to making the most of this versatile and very slightly intrusive device : bed topography, velocity field measurements, estimate of bed load velocity or suspended solid fluxes. This variety of data can be obtained rapidly and economically even in tough field conditions. Therefore Doppler profilers appear as promising tools for the study of river systems.