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What Are the Main Causes of Coastal Erosion in California?

The U.S. Geological Survey has studied more than half of California's 840 miles of coastline during the past 40 years and found 66 percent of the beaches eroding, according to a 2006 report. The studies, along with those done by many other groups interested in preserving one of California's major attractions, indicate weather and human activities are the main causes of coastal erosion.

El Nino
- An El Nino winter brings heavy winds and high waves to the California shore.
  
  The USGS has been tracking the relationship of erosion along California's coastline to strong storms brought by El Nino winters since the 1950s. Its reports show an increase in erosion beginning in the mid-1970s, when agencies such as the National Oceanic and Atmospheric Administration reported heavier storms attributed to El Nino. An El Nino causes the winds that normally kick up cooler water in the deeper areas of Pacific to weaken and keep ocean currents warmer. The warmer currents cause a shift in the jet stream that brings strong winter storms with heavy winds and high waves to the California coast, resulting in the erosion of sand and rock.
Global Warming
- An increase in sea level combined with an El Nino storm poses a threat to homes near the shore.
  
  The California Ocean Protection Council projects a sea level increase of 10 to 17 inches on the California coast by the year 2100 as a result of melting glacial ice. In El Nino years, this could mean a corresponding increase in damage to the coastline caused by higher waves and increased flooding.
Human Activity
- Sand dunes and vegetation protect against erosion of sand from beaches.
  
  Human activities have also affected the erosion of California beaches. These include damming of lakes and creeks that replenish beaches with rock and sand; mining sand from the beaches; and building artificial seawalls that prevent normal movement of sand replenishment. Other activities such as riding off-road vehicles and hiking on coastal landforms compact sand dunes that help absorb waves and flooding during storms. Housing and hotel developments also raze dunes to improve views to the same effect. Dredging channels to drain wetlands interferes with the natural movement of sand and removes plants and animal nests that prevent erosion.
Human Help
- Sand is sometimes added to beaches to replace that lost from storms and erosion.
  
  The California Coastal Light Detecting and Ranging Project is using its remote sensing technology to collect ongoing topographical information and elevation measurements of the California coast. Its data will help plan safe, erosion-proof projects along California's coast, and identify buildings that are at risk for falling into the ocean because of erosion. The California Coastal Sediment Management Workgroup has published the "California Beach Erosion Assessment Survey 2010" outlining a master plan for managing the sediment along California beaches that includes replenishing sand and reporting their findings of Beach Erosion Concern Areas (BECAs) to state, federal or local agencies.

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