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|Title:||Changes in sand level on the beach and shelf at La Jolla, California|
|Authors:||Scripps Institution of Oceanography|
United States. Army. Office of the Chief of Engineers
Inman, Douglas Lamar, 1920-
Rusnak, Gene A.
|Keywords:||Sedimentation and deposition|
Sand level changes
|Publisher:||United States, Beach Erosion Board|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Technical memorandum (United States. Beach Erosion Board) ; no. 82.|
Abstract: Changes in the level of the sandy bottom were measured periodically over an interval of almost three years at stations extending from near the surf zone to a depth of 70 feet. A reference level was established at each station by forcing six rods, spaced at intervals of 10 feet , into the bottom and changes in sand level were based on the average of the differences in length of rod exposed from survey to survey. Measurements, which were performed by swimmers equipped with self-contained underwater breathing apparatus, resulted in a standard error of about + or - 0.05 foot per survey in the determination of net sand level. The total r ange in sand level probably exceeds 2 feet at the 18-foot deep station, where changes in excess of 0.6 foot were measured before the reference rods were lost. The magnitude of Change decreases with increasing depth; Changes of 0.29, 0.16, and 0.15 foot were measured at stations where the depth of water was 30, 52, and 70 feet respectively. Estimates of sand level variation, made for monthly and seasonal periods, indicate that significant changes occur between monthly periods at the 30 and 70-foot depths, and that significant seasonal changes occur at the 30 and 52-foot depths. At the deepest station overall seasonal variations are relatively small in comparison with changes of shorter period. Comparison of acoustic soundings with reference rod measurements indicated that the accuracy of the acoustic sounding method was of the order of + or - 1/2 foot for these operating conditions.
|Appears in Collections:||Technical Memorandum|