Coastal Erosion in CA

 Societies worldwide are faced with new challenges in mitigating and adapting to the effects of climate change. One of the major environmental effects of global temperature increases will be a continued increase in the rate of sea level rise. Higher temperatures cause sea level rise through the melting of ice on land (eustatic increases) and through the thermal expansion of water (steric increases) (Cayan et al, 2008).

One of the direct physical outcomes of sea level rise is coastal inundation. While inundation will be more pronounced on low-lying, heavily urbanized coastlines, it will still affect the Monterey Bay area. In both Monterey and Santa Cruz Counties, urbanized areas directly adjacent to estuaries and the coast will be threatened by higher high tides. While the rise may not be a direct threat to infrastructure, businesses, or residences, it may overwhelm agricultural land, degrade wetland ecosystem services, and will raise the base level to allow for more devastating storm events. Wetlands that worked as flood barriers and groundwater filters will have less functional area. Natural wetland retreat due to the increase in base level will be halted by adjacent urbanization and hard barriers (Pethick, 2001). Saltwater intrusion can damage upstream ecosystems and water availability (EPA, 2008).

Some of the Monterey Bay’s major natural assets are its long sandy beaches, which act as natural buffers to coastal flooding and are important attractions for the dominant tourism industry. The littoral cells operating within the bay are highly active, but are not at equilibrium. The southern stretch of the beach, near Seaside, already has the highest average erosion rate in California (AMBAG, 2008). In addition, the dunes that work as a continued source of sediment and as a flood buffer during storm surge events have been eroding along the entire southern Monterey Bay coastline at up to six feet per year since 1970 (Hapke et al, 2006). Erosion rates are expected to increase due to rising mean sea level. Zhang et al (2004) found that the erosion rate on Atlantic Coast beaches is about two orders of magnitude greater than the rate of sea level rise.

Beach nourishment has been highlighted recently as a solution to coastal erosion; proponents of this alternative maintain that increasing beach width by physically adding sand to a beach buffers wave energy and slows retreat rates. Federal, state and local government agencies are pursuing this method as a way to protect property from erosion damage, but the costs are generally very high and the net, long-term benefits of beach nourishment will vary greatly depending on local conditions (Leonard et al. 1990). By far the most popular option to manage shoreline retreat in California has been the construction of coastal protection structures (also referred to as coastal armoring). Approximately 10% of California’s coastline is currently armored (Griggs in press-a). The complexity and significance of coastal armoring in California are evidenced by numerous scientific studies, involvement of non-profit organizations, such as the Sierra Club and the Surfrider Foundation, and media coverage of the issue, such as KQED’s Coastal Clash documentary (http://www.kqed.org/w/coastalclash/home.html). The costs of armoring can be significant; millions of federal, state and private dollars have been expended annually on shore 3 protection, which can cost anywhere from $1800 to $7600 per linear foot of coast (Griggs in press-a).

http://www.mbari.org/education/internship/08interns/08papers/Crook.pdf

http://montereybay.noaa.gov/resourcepro/resmanissues/coastal.html

http://montereybay.noaa.gov/resourcepro/resmanissues/pdf/022305armoring.pdf