Sediment Management for Southern California Mountains, Coastal Plains and Shoreline. Part A: Regional Geological History
Creators: name: Fall, Edward W.
Publisher: name: California Institute of Technology
Year: 1981

description: In southern California the natural environmental system involves the continual relocation of sedimentary materials. Particles are eroded from inland areas where there is sufficient relief and, precipitation. Then, with reductions in hydraulic gradient along the stream course and at the shoreline, the velocity of surface runoff is reduced and there is deposition. Generally, coarse sand, gravel and larger particles are deposited near the base of the eroding surfaces (mountains and hills) and the finer sediments are deposited on floodplains, in bays or lagoons, and at the shoreline as delta deposits. Very fine silt and clay particles, which make up a significant part of the eroded material, are carried offshore where they eventually deposit in deeper areas. Sand deposited at the shoreline is gradually moved along the coast by waves and currents, and provides nourishment for local beaches. However, eventually much of this littoral material is also lost to offshore areas. 

Human developments in the coastal region have substantially altered the natural sedimentary processes, through changes in land use, the harvesting of natural resources (logging, grazing, and sand and gravel mining); the construction and operation of water conservation facilities and flood control structures; and coastal developments. 

In almost all cases these developments have grown out of recognized needs and have well served their primary purpose. At the time possible deleterious effects on the local or regional sediment balance were generally unforeseen or were felt to be of secondary importance. 

In 1975 a large-scale study of inland and coastal sedimentation processes in southern California was initiated by the Environmental Quality Laboratory at the California Institute of Technology and the Center for Coastal Studies at Scripps Institution of Oceanography. This volume is one of a series of reports from this study. Using existing data bases, this series attempts to define quantitatively inland and coastal sedimentation processes and identify the effects man has had on these processes. To resolve some issues related to long-term sediment management, additional research and data will be needed. 

In the series there are four Caltech reports that provide supporting studies for the summary report (EQL Report No. 17). These reports include: 

EQL Report 17-A Regional Geological History 

EQL Report 17-B Inland Sediment Movements by Natural
Processes 

EQL Report 17-C Coastal Sediment Delivery by Major
Rivers in Southern California 

EQL Report 17-D -- Special Inland Studies 

Additional supporting reports on coastal studies (shoreline
sedimentation processes, control structures, dredging, etc.) are being published by the Center for Coastal Studies at Scripps Institution of Oceanography, La Jolla, California.
description: Copyright 1981 by California Institute of Technology. 

The author wishes to acknowledge the generous assistance of his wife, Theresa Fall, in preparing the graphics and reviewing the manuscript. Also much appreciated is the skillful typing of Carol Boyd, Jeri Lucas and Debra Brownlie, as well as technical and editorial reviews by Dr. Robert P. Sharp and Diane Davis. 

Support for this project was provided through grants and contracts from:

Ford Foundation, Grant No. 795-0092 

Los Angeles County Flood Control District, Agreement No. 27272. 

Orange County Environmental Management Agency.

State of California Department of Boating and Waterways, Agreement No. 9-42-133-20 

United States Geological Survey, Contract No. 14-08-001-16826 and Grant No. l4-08-000l-G-605 

Department of the Army, Corps of Engineers, South Pacific Division, Contract No. DACW 09-77-A-0040 

United States Forest Service, Pacific Southwest Forest and Range Experiment Station, Agreement No. 21-587 

National Science Foundation, Grant No. ENG-77-l0l82 

Southern Pacific Corporation 

EQL Discretionary Funds 

In addition, the U.S. Geological Survey and the U.S. Forest Service have provided research personnel to work with the project team at EQL. Finally, the universities, Caltech and University of California, San Diego, provided the institutional framework for conducting the study.