The exact mechanism of transport into these canyons is not clear, even for 

 the La Jolla Canyon (California) which is stated to be the most extensively 

 studied submarine feature in the wDrld (Shepard and Buffington, 1968). Once 

 inside the canyons, the sediment travels down the floors of the heads of the 

 canyons and is permanently lost to the littoral zone. 



f. Deflation. The loose sand that forms beaches is available to be 

 transported by wind. After a storm, shells and other objects are often found 

 perched on pedestals of sand left standing after the wind has eroded less 

 protected sand in the neighborhood. Such erosion over the total beach surface 

 can amount to significant quantities. Unstabilized dunes may form and migrate 

 landward, resulting in an important net loss to the littoral zone. Examples 

 Include some dunes along the Oregon coast (Cooper, 1958), between Pismo Beach 

 and Point Arguello, California (Bowen and Inman, 1966); central Padre Island 

 (Watson, 1971); and near Cape Henlopen, Delaware (Kraft, 1971). Typical rates 

 of transport due to wind range from 2.5 to 25 cubic meters per year per meter 

 (1 to 10 cubic yards per year per foot) of beach front where wind transport is 

 noticeable (Cooper, 1958; Bowen and Inman, 1966; Savage and Woodhouse, 1968; 

 Gage, 1970). However average rates probably range from 2.5 to 7.5 cubic 

 meters per year per meter (1 to 3 cubic yards per year per foot). 



The largest wind-transported losses are usually associated with accreting 

 beaches that provide a broad area oi loose sand over a period of years. Sand 

 migrating inland from Ten Mile River Beach in the vicinity of Laguna Point, 

 California, is shown in Figure 4-48. 



Study of aerial photographs and field reconnaissance can easily establish 

 whether or not important losses or gains from wind transport occur in a study 

 area. However, detailed studies are usually required to establish the 

 importance of wind transport in the sediment budget. 



g. Carbonate Loss . The abrasion resistance of carbonate materials is 

 much lower than quartz, and the solubility of carbonate materials is usually 

 much greater than quartz. However, there is insufficient evidence to show 

 that significant quantities of carbonate sands are lost from the littoral zone 

 in the time scale of engineering interest through either abrasion or solution. 



h. Mining and Dredging . From ancient times, sand and gravel have been 

 mined along coasts. In some countries, for example Denmark, and England, 

 mining has occasionally had undesirable effects on coastal settlements in the 

 vicinity. Sand mining in most places has been discouraged by legislation and 

 the rising cost of coastal land, but it still is locally important (Magoon, et 

 al. 1972). It is expected that mining will become more important in the 

 offshore area in the future (Duane, 1968; Fisher, 1969). 



Such mining must be conducted far enough offshore so the mined pit will 

 not act as a sink for littoral materials, or refract waves adversely, or 

 substantially reduce the wave damping by bottom friction and percolation. 



Material is also lost to the littoral zone when dredged from navigable 

 waters (channels and entrances) within the littoral zone and dumped in some 

 area outside of the littoral zone. Material can be dumped in landfill areas 

 or in deep water offshore. This action has been a common practice because it 

 lowers the first costs for some dredging operations. 



4-124 



