Harbors 



317 



require continuous or intermittent removal. 

 Studies of problems of filling of the various 

 harbors have been sponsored by the Army 

 Beach Erosion Board: Santa Barbara (Trask, 

 1952), Port Hueneme (Savage, 1957), Santa 

 Monica (Grant and Shepard, 1939; Handin 

 and Ludwick, 1950), and Anaheim Bay 

 (Caldwell, 1956). Published studies by 

 other organizations and individuals have for 

 the most part been related to other aspects 

 of the harbor sediments than rates of filling. 



The two large harbors, Los Angeles-Long 

 Beach and San Diego, have had little dif- 

 ficulty with silting up, owing to their posi- 

 tions on the lee sides of submarine canyons 

 which reach close to shore and on the lee 

 side of large rocky points. Artificial modi- 

 fication has consisted of construction of a 

 multimillion-dollar breakwater and mole at 

 Los Angeles-Long Beach (McQuat, 1951), 

 dredging of deep ship channels, and erec- 

 tion of wharves and warehouses (Board of 

 Harbor Commissioners, 1957). 



All the harbors are subject to oceano- 

 graphic and geologic influences other than 

 sediments, some of which are more easily 

 controlled than others. A common factor 

 introduced by organisms is the destruction 

 of wooden pilings by certain isopods and 

 mollusks. In some of the harbors, such as 

 Los Angeles-Long Beach, discharges of in- 

 dustrial and sewage wastes during the past 

 have been greater than could be eff'ectively 

 diluted by circulation, so the oxygen content 

 of the water dropped to zero and hydrogen 

 sulfide formed. Under these conditions 

 borers could not become established and the 

 pilings were safe (Barnard, 1958). When 

 fishing and other interests required the 

 waste discharge to be improved, the borers 

 appeared along with some of the fish that 

 were desired. Reducing the effects of borers, 

 concrete has sometimes been used as a sub- 

 stitute for wooden pilings, as well as for sea 

 walls, breakwaters, outfalls, and other ma- 

 rine structures. Tests of concrete blocks at 

 San Pedro showed no deterioration by sea 

 water in a period of 27 years (Mather, 1957). 

 Similarly, a pozzolanic concrete pier from 

 near Naples, Italy, was found to be in excel- 

 lent condition, despite centuries of immer- 



sion in sea water (Drury, 1954). In fact, 

 sea water has been used in mixing of con- 

 crete (Narver, 1954; Krynine and Judd, 1957) 

 with satisfactory results. 



Waves have several interesting effects on 

 sea walls and breakwaters. At Redondo 

 Beach erosion caused by depletion of the 

 beach resulting from construction of the 

 partial breakwater was off'set by construc- 

 tion of a sea wall using blocks of grano- 

 diorite (Fig. 240). The blocks, set loosely 

 atop the sand, pebble, and cobble foreshore, 

 were repeatedly undermined by wave action 

 so that they settled a meter or two during 

 winters and the waves hurled cobbles and 

 even small boulders over the sea wall and 

 into adjacent houses. Repeated rebuilding 

 and addition to the sea wall were necessary 

 from 1945 to completon of the harbor break- 

 water in 1958. The ability of storm waves 

 to move huge blocks of breakwaters and sea 

 walls is attested by studies of Cornish (1912), 

 Johnson (1919), and others. In the southern 

 California region storm waves of September 

 1939 destroyed the lighthouse at what was 

 then the Long Beach end of the main break- 

 water in San Pedro Bay, about 1 km of a small 

 breakwater at the mouth of Los Angeles 

 River, and several piers at Seal Beach, Hunt- 

 ington Beach, Laguna Beach, and San Clem- 

 ente. Other storms have torn large gaps in the 

 breakwaters at Santa Monica and Redondo 

 Beach. Measurements of the forces exerted 

 by waves in the region are scanty, although 

 computations have been made of wave 

 power from measurements of wave length, 

 height, and period (Luplow, 1950; Johnson, 

 1953). Some tank studies were made by 

 O'Brien and Morison ( 1 952). Dynamometer 

 measurements (Fig. 241) by Lindsay (1957a) 

 showed that waves averaging about 50 cm 

 high at Zuma Beach (west of Point Dume) 

 produced forces of as much as 10 pounds 

 per square foot (5 gm/sq cm). Forces de- 

 veloped by storm waves are enormously 

 greater. For example, Johnson (1919, pp. 

 63-65) reported that impact forces of storm 

 waves at Scotland reached 6000 pounds per 

 square foot, 600 times the forces measured 

 by Lindsay. 



One of the most interesting problems con- 



