Redondo Beach King Harbor, California, Design for Wave Protection: Coastal Model Investigation Final Report

A 1:75-scale, three-dimensional hydraulic model was used to investigate the design of proposed breakwater modifications at Redondo Beach King Harbor, California, with respect to wave conditions in the harbor. The model reproduced approximately 8,800 ft of the California shoreline and included the existing harbor and offshore bathymetry in the Pacific Ocean to a depth of -60 ft. Improvement plans consisted of raising the crest elevation of portions on the north breakwater both with and without installing a transition layer of smail stone, and extending the length ard crest elevation of the south breakwater. An 80-ft-long unidirectional, spectral wave generator, and an Automated Data Acquisition and Control System were utilized in model operation. It was concluded from test results that:
a. Existing conditions are characterized by very rough and turbulent wave conditions with wave heights up to 8 ft along the moles for 50-year conditions. b. Of the original improvement plans tested with the seaward wing of the north breakwater raised to an elevation of +20 ft (Plans I through 7), Plan 6 provided the greatest wave protection within the harbor. Wave heights along the moles exceeded the criteria, however, by 1.0 ft for 50-year conditions. c. Of the improvement plans tested with portions of the north breakwater raised to elevations of +24 and +20 ft (Plans 8 through 10), Plan 9 provided the greatest wave protection within the harbor. Wave heights exceeded the criteria along the moles by 0.7 ft for 50-year wave conditions. d. Of the improvement plans tested with the seaward wing of the north breakwater sealed with small stone and raised to an elevation of +20 ft (Plans 10 through 14), Plan 12 provided the greatest degree of wave protection to the harbor. For 50-year wave conditions, wave heights met the established waveheight criteria along the moles within the harbor. e. Of all the improvement plans tested (Plans I through 14), Ilan 14 was considered optimal considering wave protection and construction costs. f. Comprehensive wave-height tests conducted for Plan 14 indicated that the established wave-height criteria in the harbor would be met or only slightly exceeded for waves up to a 100-year recurrence from 240 and 260 deg. Waves in excess of 10 ft in height from 220 deg, however, in some cases, will significantly exceed the criteria particularly at Mole D and the entrance to Basin 3.