Coastal Literature Search

Sediment containing 80% sands and 20% fines (i.e 80/20) historically has been considered to contain the maximum amount of fine-grained materials suitable for use in a beach nourishment project by the USEPA and other agencies that follow the USEPA lead. Use of source materials containing a higher percentage of fines has typically been discouraged unless a high degree of background information on sediment movement patterns and potential impacts on ecological habitats in the vicinity of the project is available. The 80/20 ratio is a "rule of thumb" as opposed to an actual regulation, and we have identified and provided known information on this rule of thumb in the links below.

The 80/20 rule of thumb was originally developed as guidance for when regulatory rules applicable to ocean dumping become relevant and morphed into assessments as to whether placing sediment on a beach was considered ‘dumping’ or ‘nourishment’. Also important was the conclusion that sediment with greater that 20% fines had the potential to, due to adsorption capabilities of the fines, contain hazardous chemicals.

This topic was an integral part of CSMWs Sand Compatibility and Opportunistic Use Program, (SCOUP) which included a process vetted by regulatory agencies on how ‘Less Than Optimum’ (i.e., greater than 20% fines) sediment could be used for beach nourishment projects. In addition, CSMW initiated, partially funded and participated in a multi-agency demonstration project to evaluate the impacts associated with using high percentage fines sediments for beach nourishment at the Tijuana Estuary.

• B. Ross Memo to EPA HQ
• EPA HQ Letter to Santa Cruz Harbor
• EPA HQ Letter to Cresent City Harbor
• EPA HQ Letter to CMANC

• Offshore Sand Deposits, Southern California - tabulates selected sites of offshore sand deposits from Santa Barbara - San Diego counties
• Offshore Potential Sediment Sources - discusses known information regarding the distribution of sediment types on the seafloor along the coast and provides related references

Littoral Cell, Sand Budgets and Beaches

People have been interested in beaches and coastal processes for many years. It has been observed that beach width can change significantly over a range of time periods, from hours and days to years and decades. Long-term erosion/narrowing of California’s beaches is of great concern to coastal managers as well as the general public, since habitat, recreational opportunities and shore protection are adversely affected by such loss.

The coastline of California can be separated into distinct, essentially self-contained regions or cells that are geographically limited. For example, beach sand in the Santa Barbara area originates from the watersheds and the coastline in the Santa Barbara area, while beach sand in San Diego or Santa Cruz comes from within those geographic areas.

Coastal geologists and engineers call these self-contained coastal units “littoral cells”. These cells are geographically limited and consist of a series of sand sources (such as rivers, streams and eroding coastal bluffs) that provide sand to the shoreline; sand sinks (such as coastal dunes and submarine canyons) where sand is lost from the shoreline; and longshore transport or littoral drift that moves sand along the shoreline. Understanding this setting allows researchers to focus on the major elements influencing specific beach or shoreline areas. This report illustrates how sand moves from one location to another within littoral cells.

It is the balance between the volumes of sand entering and leaving a littoral cell over the long-term that govern the long-term width of the beaches within the cell. Scientists use the concept of sand budgets to identify and quantify, to the degree possible, additions and losses of sand that influence beach width. Where sand supplies have been reduced through the construction of dams or debris basins in coastal watersheds, through armoring of the seacliffs, by mining sand or restricting littoral transport through large coastal engineering structures, the beaches may temporarily or permanently narrow. Sand budgets are illustrated and then summarized for California’s major littoral cells.

Beach nourishment or beach restoration is the placement of sand on the shoreline with the intent of widening a beach that is naturally narrow or where the natural supply of sand has been significantly reduced through human activities. Nourished shorelines provide a number of benefits including increased area for recreation, increased revenue from tourism, habitat improvement for shore dependant species, greater protection of the coastline from coastal storms, reduced need for armor, and increased public access. While nourishment may appear to be an attractive alternative to coastal armoring or retreat, this report describes a number of issues or considerations that need to be carefully considered and addressed. Sand retention systems have been used effectively at a number of sites in California as a way to significantly extend the lifespan of a beach nourishment project.

The CSMW and the University of California at Santa Cruz, have developed this report as an educational tool as part of their public outreach effort associated with the Sediment Master Plan. A more detailed report on specific sand budgets for California’s major littoral cells is a complement to, and resource for this more general discussion. The document was prepared with significant input from CSMW personnel, but does not necessarily represent the official position of member agencies.