Search

The primary objective of our studies in FY13 was to develop, test, and improve models for nearshore processes near and within inlet channels. In addition, we continued analysis of our Skagit tidal flats measurements, compared observations with numerical simulations of waves propagating across the shallow, muddy, Louisiana continental shelf, estimated surfzone vorticity and short-crested breaking waves (with David Clark), and investigated the evolution of rip currents and the associated bathymetric channels.

The long-term goal is to determine the contribution of short-crested breaking waves to vorticity (and thus mixing) in nearshore regions and near strong flows from inlets or river mouths.

The long-term goal is to develop field-verified models for the evolution of surface-gravity waves, circulation, sediment transport, and the subsequent morphological response in shallow, coastal waters. The objectives of our studies in FY11 were to analyze observations of currents, waves, and bathymetry on tidal flats, and to develop, test, and improve models for tidal-flat processes. Specific goals related to tidal flats were to investigate the relative importance of riverine and tidal flows to the circulation and density stratification. Additional goals in FY11 included developing models for mud-induced dissipation of waves, analyzing waves, currents, and morphological change on sandy beaches, providing ground truth for remote sensing of littoral areas, and planning a study of waves and circulation in the vicinity of a strong, narrow jet of water at an inlet. Our approach is to collect field observations to test existing hypotheses, to discover new phenomena, to provide ground truth for remote sensing studies, to initialize and test data assimilative models that invert for bathymetry, and to calibrate, evaluate, and improve models for tidal flat hydrodynamics and morphological evolution and for waves propagating in shallow water across muddy and sandy seafloors.

Our long-term goal is to use remote sensing observations to constrain a data assimilation model of wave and circulation dynamics in an area characterized by a river mouth or tidal inlet and surrounding beaches. As a result of this activity, we will improve environmental parameter estimation via remote sensing fusion, determine the success of using remote sensing data to drive DA models, and produce a dynamically consistent representation of the wave, circulation, and bathymetry fields in complex environments.

The long-term objective is to develop field-verified models for the wave fields, circulation patterns, and morphological evolution near inlets and river mouths. Our approach is to collect and analyze field observations of waves, currents, winds, and bathymetry to test hypotheses and to calibrate, evaluate, and improve numerical models.

The long-term goal is to develop field-verified models for the evolution of surface-gravity waves, circulation, sediment transport, and the subsequent morphological response in shallow waters on sandy and muddy coasts and on macrotidal flats.

The long-term goals are to understand and model the transformation of surface gravity waves propagating across the nearshore to the beach, the corresponding wave-driven circulation, and the associated evolution of surfzone morphology.

This project provided funds for initial investigations about the behavior of a large hole in the surfzone. A backhoe was used to create a 10-m diameter, 2-m deep hole that simulated the change to the morphology caused by an explosion near the shoreline. The hole was created near the water line at low tide, and instrumented with many acoustic Doppler current meters. As the tide rose, continuous surveys of the bathymetry within and near the hole were performed, allowing detailed investigation of the evolution of the bathymetry as waves reached and overtopped the hole. Waves and currents were measured from offshore of the hole (about 2-m water depth) to near the landward extent of the run up above the hole. As water reached the altered beach topography, sediment was transported such that the hole began to fill (a combination of collapse of the sides of the hole and sediment transport towards the hole). The hole was filled, and the beach face returned to its initial configuration within one tidal cycle. The experiment was performed 3 times, first to gain experience creating a hole, second to learn how to instrument the hole rapidly, and the third to monitor in detail the waves and currents within the hole. Graduate student Jim Thomson analyzed the current meter data and surveys to show that the water in the hole formed a seich with frequency of oscillation that changed as the hole evolved from circular to semi-circular. The observed frequencies were similar to those predicted for a circular basin and for a semi-circular resonator. Dye patterns showed the path of water (and thus of sediment or other tracers in the water) as the hole evolved and slowly filled in.

The long-term goals are to understand the transformation of surface gravity waves propagating across the nearshore to the beach, the corresponding wave-driven circulation, and the associated evolution of surfzone morphology. The objective of the Nearshore Canyon Experiment (NCEX) is to understand the effect of complex continental-shelf bathymetry on surface gravity waves and on the breaking-wave-driven circulation onshore of the irregular bathymetry. Primary objectives this year were quality control processing of all the data in anticipation of public release on 1 January 2006, and analysis of infragravity wave reflections and bathymetric changes. Additional objectives of our research are to test hypotheses for nearshore waves, currents, and morphological change with previously obtained observations.

The long-term goal is to develop and verify models for fluid and sediment processes in the swash zone.

The long-term objective is to develop models that predict the generation, evolution, migration, and destruction of seafloor megaripples (bedforms with lengths of order of 1-2 m and heights of order 10 s of cm) given geological (sediment characteristics, underlying geological framework) and hydrodynamical (waves and currents) conditions.