EFFECTS OF PROPOSED HARBOR MODIFICATIONS ON WAVE CONDITIONS, HARBOR RESONANCE, AND TIDAL CIRCULATION AT FISH HARBOR, LOS ANGELES, CALIFORNIA: PHYSICAL AND NUMERICAL MODEL INVESTIGATIONS

The Port of Los Angeles has embarked upon a program to improve wave and current conditions at Fish Harbor, Los Angeles, California. To achieve this, field measurements (both wave heights and currents) for the existing harbor were obtained and analyzed and a physical hydraulic model for short-period wave tests and numerical models for harbor oscillation and tidal circulation were used to investigate the effects of proposed harbor improvements. The proposed improvements consisted of dredging deeper channels and berthing areas to accommodate the larger, deeper draft vessels using the harbor and the creation of landfills to provide for expansion of local industry. The physical model was constructed to an undistorted scale of 1:60, model to prototype, and included the entire harbor and approximately 1,500 ft of underwater contours to the south and east of the entrance. A 30-ft-long wave generator and an automated data acquisition and control system were utilized in model operation. A hybrid finite element numerical model (capable of calculating forced harbor oscillations for harbors of arbitrary shape and variable depth) was used to calculate harbor resonance at Fish Harbor. Four numerical finite element grids were used to compute wave-height amplification factors and normalized maximum current velocities associated with the harbor's response to incident waves ranging from 20 to 160 sec. A two-dimensional depth-averaged formulation of the hydrodynamic equations was used in the tidal circulation model, and an implicit-explicit finite difference scheme was used to numerically solve the equations. An optimum improvement plan was developed during the physical model wave tests. The plan met the established wave-height criteria and provided increased area for mooring small craft in the lee of the harbor breakwater. The results of the long-period prototype data analysis and numerical harbor oscillation study indicated a decrease in long-period wave energy for this optimum plan. The tidal circulation study indicated that changes in tidal circulation characteristics were limited to the vicinity of Fish Harbor and included a slight shift in flood and ebb flow patterns due to the breakwater location for the optimum plan. Tidal flushing in Fish Harbor was influenced by the optimum plan but was similar to existing conditions for successive low waters.