Coastal erosion in the United States is responsible for approximately $500 million in property loss, land loss and property damage. To help alleviate coastal erosion, the federal government spends an average of “$150 million every year on beach nourishment and other shoreline erosion control measures” (NOAA). In addition to beach erosion, more than 80,000 acres of coastal wetlands are lost annually approximately the “equivalent of seven football fields disappearing every hour of every day” (NOAA). The result is that the United States lost an area of wetlands larger than the state of Connecticut between 1998 and 2016. Coastal erosion threatens to damage nearly 87,000 homes along the shoreline of the United States in the next 60 years, according to a report released in 2000 by FEMA. Population growth, rising sea levels, hurricanes, dams (that block the resupply of sand to beaches) and severe storms associated with El Niño events are escalating concerns that damage from shoreline erosion could cost hundreds of millions more in coming decades. In California, these concerns are intensified by demo-graphics and geography: about 80 percent of the state’s 34 million residents live within 50 kilometers of the ocean and about 86 percent of the state’s shoreline is classified as actively eroding. Coastal bluff erosion is of particular concern in counties such as San Diego where homes have been built on landslide-prone bluffs and where heavy surf scours the shore. In this paper I will discuss the implications of coastal erosion specifically around the La Jolla coast in Southern California. My paper topic will focus on the increase of wave energy affecting the coastal sea cliffs and beaches in the San Diego area. The highways and coastal communities in the greater San Diego area are under continued threats of erosion and collapse of their foundations due to large wave events. The cliff top communities are growing exponentially due to population boom. I will investigate the rate at which the cliffs are receding, why they are receding, the effect on the coastal communities, the most important ecological and non-ecological factors and multiple ways to help prevent the erosion of these cliffs.
Coasts, as boundaries between land and water, are characterized by the geologic nature of the land, which is unstable and often fragile, and the dynamic power of wind and sea. As a result, coastal environments are constantly changing as they seek to achieve and maintain equilibrium among the many opposing natural forces. The vibrant beauty of shore areas is attracting a growing population; however, the ever-changing character of coasts makes them hazardous for people and, in the long term, for buildings and structures. The risks associated with living along a coast are comparable to those experienced by people living on a river flood plain, near an earthquake fault, or close to a volcano — all carry the possibility of eventual catastrophe.
Cliff Erosion
A three-year study conducted by University of Illinois Engineering professor Sean Vitousek shows that approximately 31 to 67 percent of beaches in the La Jolla and Torrey Pines (northern suburbs of San Diego) maybe totally eroded by 2100 if sea level rises stay at 3-6.5 feet. The cliffs around the La Jolla area historically erode at about 8 inches per year. This is about 4 inches less than the retreat in the Torrey Pines are (about 10 minutes north of La Jolla) as the cliffs are made of softer material in Torrey Pines. However when you couple the natural retreat with that of sea level rise the effects are dramatic. Cliffs may retreat at approximately 16 inches in the La Jolla region and about 23.6 at Torrey Pines per year. In natural environments erosion of the cliffs adds sand to the beach below but retaining walls, sea walls and human intervention does now allow sand to infill the beaches below the cliffs therefore exacerbating the already ongoing issues.
Beach Nourishment
As sand naturally acts as a protective layer from sea level rise, the cliffs not replenishing lost sand make sea level rise a much more dangerous problem which in turn leads to more flooding. Vitousek and his team conducted a study to see if adding large amounts of sand to beaches with significant sand loss would help mitigate erosion. His studies found that adding sand did in fact slow down erosion. This may seem like a good thing, however these areas are protected marine zones and conducting beach nourishment in these areas is prohibited due to the possible effects on the ecosystem.
Locals in the La Jolla area are pushing for retaining walls to help combat cliff erosion. This option is viable to preserve the cliffs, however this leaves the beach to erode completely leaving just cliffs that drop straight into the water.
Implications on Housing and Businesses
San Diego is the 2nd most populous city in California and 8th most populous in the Country. According to the U.S Census Bureau, between July 1, 2016 and June 30th of 2017, San Diego added 15,715 residents (10th largest population increase in the country). This population increase has caused an increase in houses built in geographically desirable locations i.e. high cliffs overlooking the ocean. These houses are beginning to collapse as the cliffs fall out from below them. People are forced to vacate or sell their homes as the cliffs recede. There have been injuries and deaths directly linked to the collapse of homes in these areas. Businesses are having to be shut down and relocated due to safety concerns. Since many of these sea cliff areas are hazardous, individuals who wish to develop commercially or residentially along the coast must apply for and obtain a coastal development permit and obtain a building permit to ensure the development is build according to safety codes which include how close a structure is to a cliff, the type of soil underneath and the rate in which cliffs are retreating. People who wish to build along the cliffs must bring in structural and environmental engineers to monitor the implications that will inevitable occur when building on cliffs.
Case Study in Detail
Building off Sean Vitousek’s work listed above, he and his team presented a Coastal One-line Assimilated Simulation Tool (CoSMoS-COAST) to predict the short term and long term shoreline response to climate change in the 21st century.
The CoSMoS-COAST model measured the sea level rise by equating the mean sea level rise as zero in 2000. Any increase past zero (year 2000) is considered a rise in sea level. The model calculated four sea level scenarios including holding the line and no beach nourishment (1), holding the line and beach nourishment (2), no holding the line and no continued nourishment (3), and no holding the line and beach nourishment (4). Holding the line effectively means shoreline armoring; attempting to preserve the shoreline through the use of “jetties, offshore breakwaters, sea walls or other hardened beach structures” (Coastalcare).