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of sediments calculated by various authors are based upon 



conditions existing at the present time, but the volume has 



varied greatly. Numerous natural and artificial changes in 



the drainage areas have taken place within historic time which 



have greatly altered the sedimentary regime of Santa Monica 



Bay, The following is a partial list of some of the most 



significant changes: i 



lo Construction of storm drains and debris basins 

 which have greatly altered the former natural drainage and 

 as a consequence, the amount of detritus reaching the bay, 



2, Construction of the coast highway which has 

 prevented cliff erosion. On the other hand, large quantities 

 of sediment have been dumped along the coast in order to 

 widen the highway, Davidson (in Cong, Docs,, 1897) reported 

 that in 1872 when traveling in a wagon along the northern 

 part of Santa Monica Bay, the cliffs came so close to the 

 shore and the canyons were so steep, that he could only pass 

 this region at low tide. As proof of former erosion of the 

 cliffs in this region, Davidson says J 



"At Point Dume a very fierce westerly wind 

 sprang up and retarded my operations so that 

 in returning to Santa Monica I was on the 

 beach through two low waters, I found the 

 beach torn away along the whole shore line, 

 and met with rocky obstructions which in 

 some cases had been wholly uncovered by the 

 washing away of the sands. As we approached 

 Santa Monica the evidences of this destructive 

 action became more and more marked, and for 

 the last 2 or 3 miles the beach was torn away 

 from 10 to 12 feet in depth," 



3, Urban development has stabilized erosion over 



most of the coastal plain and parts of the Santa Monica Mountains, 



4, Widening of beaches by artificial nourishment, con- 

 struction of breakwaters, and by the use of groins and jetties. 

 The construction of coastal engineering structures above Pt. 

 Dume has also cut off large amounts of sediments that may have 

 reached the bay in the past, 



5, Beach erosion by the construction of breakwaters, 

 i.e., downcoast from Santa Monica and Redondo breakwaters. 



6, Streeim piracy of the westward flowing Los Angeles 

 River, and also the changes made in Ballona Creek outlet, 



7, Construction of reservoirs which have greatly 

 reduced the quantity of sediments reaching the bay. At the 

 present time only very fine material is washed over the dams 

 and reach the sea. The following are the most important 



