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Orange County Coastal Regional Sediment Management Plan 3.3.5 Sand Retention Sand that is placed upon erosive beaches without some form of retention will be short lived. Therefore, beach nourishment at highly erosive beaches can become more economical when combined with appropriate ways to retain sand. Traditional coastal structures such as groins and breakwaters have been used effectively to stabilize beaches in the past, however their use in the future is unlikely to be favored. The challenge then is to find an effective sand retention methodology that is environmentally consistent with the policies of the Orange County stakeholders. In response to this challenge, the Plan should seek ways to demonstrate and implement new and innovative sand retention technologies that are more compatible with the Orange County coastal setting and provide multi-purpose benefits of beach preservation, biological enhancement, and increased recreation opportunities. Reefs Artificial reefs have been identified as potential sand retention devices that would be compatible with permitting agencies, improve recreational opportunities, and improve hard bottom habitat (Moffatt & Nichol Engineers et. al., 2001). By breaking waves offshore, reefs can dissipate and reduce the amount of wave energy reaching the beach, thus creating a wave shadow region where sediment can fall out of suspension. The wider beach in the lee of a reef is called a salient. These multipurpose reefs are still experimental and lack proven design methods. The existing artificial prototypes have so far attained questionable or unattained expectations, some with clear negative consequences (Ranasinghe and Turner, 2006). As these types of structures are experimental, provisions for adaptive management, modification, or removal should be incorporated into the design if performance results are not achieved. Pratte’s Reef in El Segundo is a recent example of a surf mitigation reef that did not achieve expectations and was therefore removed at great expense. The City of Solana Beach has been working with USACE in pursuit of an artificial reef with the primary goal of enhancing sand retention at Fletcher Cove (Everest, 2009b). Secondary goals may be improved surfing and biological enhancement. The multi-purpose artificial reef project at Oil Piers, in Ventura County, that is being pursued in collaboration with USACE and BEACON (ASR Ltd., 2004) presents a promising submerged reef methodology that, if successful, can lead to new opportunities for innovative beach restoration, preservation, and enhancement. Both of these projects are in early stages of development, but should be monitored as the Plan is updated in the future. Dewatering Beach face dewatering is defined as the lowering of groundwater within the beach to increase natural accretion processes. This dewatering is based on the principle that the less saturated a beach face is when a wave swashes up onto it, the more water can infiltrate into the beach and less water is available to carry sand particles back down with the backwash, resulting in a net Everest International Consultants, Inc. 3.18
Orange County Coastal Regional Sediment Management Plan deposition of sand on the shoreface. Dewatering can either be active, with pumps and pipes, or passive, relying on gravity flow through buried pipes. The PEM (Pressure Equalization Module) is a commercial example of the passive approach. These dewatering technologies are relatively new and unproven in shoreline management within California. Soft Solutions There are many sand retention approaches that are considered soft solutions in that they are not constructed of rock or concrete. Beach planting is a common soft solution applied on the Gulf and Atlantic coasts. Use of geotextile, sand filled bags is considered a semi-soft solution in that the structures function similar to their hard counterparts, but are considered more temporary and removable. 3.4 Economic Impacts and Feasibility This section presents estimates of the total direct economic impact of beach spending in Orange County. It also examines the Surfside-Sunset Beach nourishment project by USACE at a very general level. It should be noted that beaches provide a number of important economic functions besides recreation. In particular, beaches act as a buffer against storm damage to inland property. Estimating these benefits is time-consuming and beyond the scope of this study, but in some cases these benefits can be larger than the recreational benefits. With sealevel rise, the benefits of the storm damage reduction are likely to be significantly higher. For examples of the economics studies of sea level rise in California, see King et. al. (2011) and Pendleton et. al. (2010). Beaches also provide ecological benefits that are more difficult to quantify in dollars. Costanza (2006) provides quantitative estimates of the ecological value of New Jersey’s shoreline habitat, though habitat value varies considerably with shoreline habitat. 3.4.1 Economic Impacts This section provides a discussion of the economic impacts of Orange County’s beach tourism, which is important for policy decisions by state, city and county officials as well as other stakeholders. A next level of analysis would be a comparison of the economic benefits to the construction cost of a particular project and beyond that would be a feasibility analysis of individual projects. Only a cursory review of the economic impacts are considered here since benefit cost and feasibility analyses would require designed alternatives with quantities, transport methods, and timelines, which is beyond the scope of the current effort. Attendance estimates are the starting point for estimating beach spending. Official data were used where available. However, many smaller beaches in Orange County do not have official estimates, in which case, attendance was based on data developed for the current study. Everest International Consultants, Inc. 3.19
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