Researchers

Chris Chickadel

Principal Oceanographer

AIRS Department

APL-UW

Affiliate Assistant Professor, Civil and Environmental Engineering

Andy Jessup

Chair, AIRS Department

Senior Principal Oceanographer

AIRS Department

APL-UW

Professor, Civil and Environmental Engineering and Affiliate Associate Professor, Mechanical Engineering

COHSTREX 2010

Sensitive video, microwave radar, and infrared sensors capture small differences in surface water temperature and surface ripple patterns — important clues to what is happening below, out of sight.

Anybody who wants to navigate a river would like to know where there are hazards to navigation, simply whether it’s deep or shallow so you can get a vessel in. It’s important for the Navy if they need to go into an area where they don’t have measurements. For operations they need to know how fast the river is flowing, how deep it is… So we are investigating the utility of remote sensing techniques to help inform them.

More About This Research

Publications

Frontogenesis and frontal progression of a trapping-generated estuarine convergence front and its influence on mixing and stratification

Giddings, S.N., D.A. Fong, S.G. Monismith, C.C. Chickadel, K.A. Edwards, W.J. Plant, B. Wang, O.B. Fringer, A.R. Horner-Devine, and A.T. Jessup, "Frontogenesis and frontal progression of a trapping-generated estuarine convergence front and its influence on mixing and stratification," Estuar. Coasts, 35, 665-681, doi:10.1007/s12237-011-9453-z, 2012.

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1 Mar 2012

Estuarine fronts are well known to influence transport of waterborne constituents such as phytoplankton and sediment, yet due to their ephemeral nature, capturing the physical driving mechanisms and their influence on stratification and mixing is difficult. We investigate a repetitive estuarine frontal feature in the Snohomish River Estuary that results from complex bathymetric shoal/channel interactions. In particular, we highlight a trapping mechanism by which mid-density water trapped over intertidal mudflats converges with dense water in the main channel forming a sharp front. The frontal density interface is maintained via convergent transverse circulation driven by the competition of lateral baroclinic and centrifugal forcing. The frontal presence and propagation give rise to spatial and temporal variations in stratification and vertical mixing. Importantly, this front leads to enhanced stratification and suppressed vertical mixing at the end of the large flood tide, in contrast to what is found in many estuarine systems. The observed mechanism fits within the broader context of frontogenesis mechanisms in which varying bathymetry drives lateral convergence and baroclinic forcing. We expect similar trapping-generated fronts may occur in a wide variety of estuaries with shoal/channel morphology and/or braided channels and will similarly influence stratification, mixing, and transport.

Remotely sensed river surface features compared with modeling and in situ measurements

Plant, W.J., R. Branch, G. Chatham, C.C. Chickadel, K. Hayes, B. Hayworth, A. Horner-Devine, A. Jessup, D.A. Fong, O.B. Fringer, S.N. Giddings, S. Monismith, and B. Wang, "Remotely sensed river surface features compared with modeling and in situ measurements," J. Geophys. Res., 114, doi:10.1029/2009JC005440, 2009.

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3 Nov 2009

Images of river surface features that reflect the bathymetry and flow in the river have been obtained using remote sensing at microwave, visible, and infrared frequencies. The experiments were conducted at Jetty Island near the mouth of the Snohomish River at Everett, Washington, where complex tidal flow occurs over a varied bathymetry, which was measured as part of these experiments. An X band (9.36 GHz) Doppler radar was operated from the river bank and produced images of normalized radar cross sections and radial surface velocities every 20 min over many tidal cycles. The visible and infrared instruments were flown in an airplane. All of these techniques showed surface evidence of frontal features, flow over a sill, and flow conditioned by a deep hole. These features were modeled numerically, and the model results correspond well to the remote observations. In situ measurements made near the hole showed that changes in measured velocities correlate well with the occurrence of the features in the images. In addition to tidal phase, the occurrence of these features in the imagery depends on tidal range. The surface roughness observed in the imagery appears to be generated by the bathymetry and flow themselves rather than by the modulation of wind waves.

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