Nested-scale Velocimetry in a River Using Infrared

River flow is driven by along-channel pressure gradients and is modified by complex bathymetry that induces secondary flow. Riverine turbulence can be generated and enhanced by flow over sharp bathymetric features, obstructions, and bedforms, which produce macro-turbulent structures [1]. Understanding these details of river flow is challenging, yet important for their direct effects on sediment transport and mixing, which in turn affect biological processes (e.g. as fish passage and pollutant dispersal) and engineering efforts (e.g. construction and flow control). Three-dimensional river flow modeling has become capable of producing realistic flow maps and turbulent structures [2], however detailed in situ measurements needed to verify models are difficult to make thus result in sparse measurements that alias highly sheared flow. Exploiting the strong temperature gradients in littoral and riverine settings, thermal infrared (IR) remote sensing [3] has been used to track and study turbulence flow patterns at the surface of an estuarine river with success. Our goal is to extend our analysis to estimating 2D surface flow patterns from the IR imagery capable of resolving large scale river flow (10m 100m) and small scale turbulence (cm m). Using the resulting surface flow maps we will plan to investigate bathymetry effects on surface flow in rivers and estuarine, quantify mean and turbulent, and provide data needed for guiding and testing river and estuary hydrodynamic models.