River Mouth and Inlet Dynamics


River Mouth and Inlet Dynamics

The project goals are to develop the capability to model, directly observe and remotely sense the dynamics of constricted river mouth or tidal inlet flows into the ocean, including wave-current interactions, the evolution of morphology, bottom bathymetry and bed roughness, physical processes of tracer dispersion, the use of drifters and unmanned vehicles in energetic environments, and assimilation of in situ and remote sensing observations into predictive models.

The experiment is located at the New River Inlet in North Carolina (Figure 1).

Figure 1: The location of the New River Inlet, North Carolina.

River mouths and inlets are natural and tactical chokepoints that exhibit a large range of physical, sedimentological, optical, and biological conditions. Safe navigation in such environments, especially in denied or restricted access areas requires better knowledge of wave and current patterns which influence sediment transport and bathymetric changes as well as the morphological evolution of riverine and tidally-driven constricted flows.

The availability of diverse electro-optical (EO) and microwave satellite sensors shows the strength of remote sensing techniques to observe a variety of geophysical phenomena occurring at inlets and river mouths. Multi-sensor satellite data can readily provide spatial snapshots of the physical, dynamical and morphological properties of the littoral and riverine environments. The uniquely observed remote sensing signatures from multi-sensor data can describe the spatial and temporal context of the present kinematics and dynamics in such littoral and riverine environments. Fusing multi-sensor data into high-resolution numerical process models and/or combining with in-situ measurements will further

Figure 2: ERS-1 SAR image of the Chesapeake Bay outflow plume on 9 May 1992.

enhance the understanding of processes dynamics of these environments and improve predictions of its properties.

The SAR image of the Chesapeake Bay taken on 9 May 1992 by ERS-1 shows several dynamical processes occurring within the inlet and outside the mouth as strong currents (near bridge and in deep channels) push a plume into the Atlantic waters (Figure 2). The plume front is well seen due to enhanced roughness and wave breaking caused by wave-current interactions. Similarly, in Figure 3, the SPOT-4 image shows a tidal front emanating from the St. Johns River Inlet, which is formed by water moving over a shallow ebb shoal. Sediment filtering out of the river is transported to the Atlantic coast, upwelling as it crosses the shoals, forming this interesting circular flow pattern. The previous ebb-tidal front is also evident at larger distance from the inlet.

Similarly, underwater topography in coastal waters and river estuaries can be observed by SAR and EO sensors (bright area in middle of Chesapeake Bay image corresponds to shallow "middle ground" shoal, while the main shipping channel is evident as a dark band; Figure 2) as well as morphological changes of inlets and rivers due to natural and/or man-made forces. Many examples, such as the Chesapeake Bay, the Mississippi Delta, the Yellow Sea, and the European Wadden Sea are more expeditiously surveyed by satellite imagery.

Figure 3: Spot-4 image taken on 15 August 2005 over the 
St. Johns River Inlet, Jacksonville, Florida is 
encircled by a tidal front formed by a shallow ebb shoal.

Figure 4 shows an ERS-1 SAR image of the estuary of the river Guayas in Ecuador. The large island in the estuary is Isla Puna. The streaks on the water surface are very likely (at least partly) sea surface manifestations of underwater sandbanks.

Figure 4: ERS-1 image taken on 3 November 1992 of Guayas River estuary in Ecuador.

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