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Hydraulic (Physical) Modeling

Seawall Protection Structure, Great Highway, San Francisco, CA.

NCI conducted a physical hydraulic model study as part of the Ocean Beach concrete seawall design. Components of the seawall included a sheet pile cut-off wall, a wave rundown dispersion bench, a sloping stepped section, a wave runup dispersion bench, and a recurved wall. The hydraulic model investigation was utilized to determine dimensions and shape of the wall for the purpose of minimizing potential wave overtopping and beach scour. In addition, hydraulic loads on the wall were determined. The tests were conducted in a wave flume at the University of Florida using an undistorted scale of 1:10. Tests were conducted for variations in structural shape, beach elevations, stillwater levels, wave heights and wave periods. For beach scour tests, the sand was modelled following Lepetit and Leroy.

Seawall Protection, Mole C, King Harbor, Redondo Beach, CA.

NCI designed, constructed and operated an undistorted 1:15 scale hydraulic model to investigate the seawall improvements required to provide storm wave protection for the Portofino Inn in King Harbor. A hydraulic flume basin at the Hydraulics Laboratory of the University of California, Berkeley was utilized for constructing this model. Model test results verified final seawall height and shape requirements for the construction of a new recurved concrete seawall on top of an existing rock revetment. The selected design sufficiently reduced the amount of wave runup and overtopping, and provided adequate protection to the improvements located directly behind the Mole C revetment.

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Castaways Marina, Newport Beach, CA.

A physical hydraulic model study was conducted by NCI for a portion of the Upper Newport Bay estuary to study baseline conditions and assess impacts to the existing current and sediment transport environment associated with construction of a new marina. A distorted scale model approximately 18 feet by 32 feet was constructed using a unique low cost construction technique. The model was calibrated against current measurements obtained as part of the study. A series of tests was run to assess potential project impacts on local current patterns, sedimentation in navigable waters, erosion of nearby bridge piers, and floating debris accumulation.

Groin No. 1 Modifications, Ventura, CA.

NCI performed a physical hydraulic model investigation in order to optimize the design of a proposed groin improvement. An existing 1:75 scale model located at the U.S. Army Corps of Engineers Waterways Experiment Station was modified to study alternative measures for diminishing adverse rip currents that were aggravating a local beach erosion problem. Using wave gages, model sediment tracer, and dye injection, alterations to the current and sediment transport patterns were qualitatively assessed for varying stillwater levels, angles of wave incidence and wave height. The model tests identified a spur structure whose location achieved the desired current dissipation results with reduced maximum wave height exposures so that a lower cost structure cross-section could be specified.

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Pillar Point Harbor, Half Moon Bay, CA.

Physical hydraulic model tests were conducted by NCI for the Pillar Point Inner Harbor by utilizing a ripple wave tank at the University of California, Berkeley. The purpose of these model tests was to economically assess 49 alternative plans to provide optimum breakwater alignment for wave protection and adequate water circulation. A matrix of breakwater cross-sections and layouts was formulated and analyzed to select an optimum plan that achieved the desired level of wave attenuation; minimized adverse wave reflection at the specially-configured entrance; satisfied navigation maneuvering and visibility requirements; and maintained acceptable water circulation via natural tidal flushing processes. The preferred plan consisted of over 3,300 feet of rubble-mound breakwater, including a 1,200-foot detached offshore segment. NCI provided the various oceanographical wave and current studies to specify the project's design criteria; prepared the detailed structural design of the preferred plan; evaluated and approved potential quarry stone sources for the multi-layered cross-section; and provided construction inspection and consultation services.

San Francisco Marina Model Study, San Francisco, CA.

The San Francisco Marina consists of two harbors (West Harbor and East Harbor) which are physically separated by about one-half mile. NCI utilized two hydraulic models to assess shoaling and wave conditions at the harbors' entrances. The two models consisted of the Corps of Engineers' San Francisco Bay tidal hydraulic model in Sausalito and the University of California's ripple tank model in Berkeley. The purpose of these model studies was to review the existing wave conditions at the harbors' entrances by analyzing wave patterns in the ripple tank model; and to identify the shoaling pattern near the West Harbor entrance by observing site water currents in the tidal hydraulic model. Alternative protection improvements consisting of shoreline spur groins and breakwater extensions were tested in the ripple tank model to assess their impacts on harbor protection. Based on the model test results, mitigation measures were recommended to minimize shoaling impact at the West Harbor entrance and to reduce wave conditions at both harbor entrances.


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San Francisquito Creek, Hydraulic Modeling and Floodplain Mapping, San Francisco, CA.  

The purpose of this study was to produce and/or update the existing floodplain mapping along the San Francisquito Creek from HWY 280 to the San Francisco Bay.  An unsteady HEC-RAS model was developed based on the steady model.  By applying the flow hydrographs and representing the potential flow breakout locations as lateral structures, this unsteady model was able to predict the flow breakout from the creek during the extreme flood events and would predict the flood conditions along the creek more realistically and more accurately. 

 

 

The unsteady HEC-RAS model was re-calibrated using three historical flood events.  After the coincident frequency analysis (CFA) was performed by the Corps, this model was further revised, with the downstream boundary condition being updated with the water stages determined in the CFA for the index station.  The flow condition for the San Francisquito Creek was predicted with the revised unsteady model for eight flood events with the return periods of 2, 5, 10, 25, 50, 100, 250, and 500 years.  The breakout flow hydrographs at all the breakout locations along the creek were determined based on the model results, and were input into the FLO-2D model as inflow hydrographs.  The floodplain modeling was then conducted using the FLO-2D model, and the floodplain maps were generated in ArcMap.

 

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