Sediment Transport on Columbia River

SonTek/YSI Acoustic Doppler Profiler (ADP) and Acoustic Doppler Velocimeter (ADV) integrated Hydra systems were deployed near the mouth of the Columbia River from August 18 through October 21, 1997 by researchers from the U.S. Army Corps of Engineers (USGS) Waterways Experiment Station (WES) and Oregon State University (OSU). The experiment was designed to measure movement of dredged material disposed off the mouth of the Columbia River. The data gathered are to be used for improvement of numerical model predictions of sediment transport.

Three tripods were deployed at different locations, each equipped with a Hydra and an ADP. All of the Hydras were outfitted with two optical backscatter sensors and a piezoelectric crystal pressure sensor. The ADPs incorporated a conductivity cell. WES investigators required simultaneous time stamping for the measurements made in the bottom boundary layer, and the Hydra was the SonTek solution.

Excellent data were retrieved from this deployment, and a few selected examples appear below. The velocity time series from the Hydra provide a means of estimating turbulence spectra, which are consistent with model predictions (Figure 1).

Figure 1. Turbulence Spectra

Combining measured orbital velocity with the pressure record allows calculation of a directional wave spectrum, at one point revealing dominant 11-s waves propagating from the North-East (Figure 2). Temperature and salinity show significant variability and reveal sharp fronts (Figure 3). The optical backscatter sensor provides insight on the distribution of suspended sediments. Acoustical and optical methods give generally similar results (Figure 4), though with some variation due to the inherent differences between the two methods.

These examples provide a good first look at the capabilities of the Hydra package. We are certain that additional exciting data will follow as more deployments are taking place at the Columbia River and other sites. On April 5, 1998, WES and OSU deployed another four Hydra and ADP-equipped tripods off the mouth of the Columbia River to continue monitoring dredged-material disposal sites in the presence of the spring discharge plume from the river.

• ADP
• Hydra