The use of position-tracking drifters in riverine environments

Small, inexpensive GPS-equipped drifters are described for use in natural rivers and streams. The Lagrangian drifters allow for near-continuous position observations providing estimates of the mean flow field, pathways, and dispersion in natural riverine environments. A discussion of limitations and statistical methods is provided. Twenty river drifters were released in clusters in three different reaches on the Skagit River, WA, USA. The results highlight the ease of use and the broad range of information river drifters afford scientists and engineers.