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As discussed in the following paragraphs, a substantial amount of information exists on coastal erosion in California. However, in many cases, the information is not up-to-date, is written for a technical audience, is not disseminated to the public, or is focused only on specific counties or cities. For all of these reasons, erosion indicator information for the California coastline has not historically been readily available in a manner easily comprehended by the public. There are some signs that this is changing, as evidenced by the reports and data summaries with Web links discussed below.
At least 4% of California's shoreline is critically eroding, according to the report "State Coastal Program Effectiveness in Protecting Natural Beaches, Dunes, Bluffs, and Rock Shores" (T. Bernd-Cohen and M. Gordon), Coastal Management27:187-217, 1999. Living with the California Coast (G. Griggs and L. Savoy, 1985) put the estimate much higher, at 125 miles out of 1,100 miles, which is over 11%!
According to CCC staff, California makes a distinction between coastal and beach erosion, but both are treated the same in terms of legal status. Key laws include the California Coastal Act, the Beach Act, and the Public Beaches Restoration Act. The CCC does not track changes in shoreline position or beach width, nor does it compile coastal or beach erosion data. Further, an inventory of erosion "hotspots" or erosion hazard areas has not been developed. However, there is some regional and site-specific data, typically developed as part of permit applications. This type of information can be found at the CCC, the California State Coastal Conservancy, and the California Department of Boating and Waterways, but is not typically available online.
Although coastal and beach erosion are not tracked in any systematic way at the current time, a database for recording and tracking coastal bluff erosion was scheduled to be assembled in 2003-2005 by the CCC through a NOAA Coastal Fellowship Grant. When the database is assembled, it will first concentrate on a 3-county area making up approximately 25% of the state's coastline. The study area will cover the Monterey Bay National Marine Sanctuary (Monterey, Santa Cruz, and San Mateo Counties), with possibly some coverage in San Luis Obispo, San Francisco, and/or Marin Counties. This will eventually be expanded to cover the entire state. The database will be incorporated into a GIS and was scheduled to be available on-line in mid-2005.
In July 2010 it was reported that state and federal scientists were embarking on a new project to construct the most detailed map of the California coast ever assembled. The $3.3 million effort ($2.75 million funding came from California's Ocean Protection Council) will begin with researchers in an airplane flying back and forth along the coast shooting thousands of laser pulses (Light Detection and Ranging or "LIDAR") per second at the rocks, beaches and cliffs along the 1,200-mile shoreline from Mexico to Oregon, generating ultra-detailed 3-D images of the contours of the land in huge computer files. The mapping work, supervised by the National Oceanic and Atmospheric Administration, will start in August 2010 and is expected to conclude by December 2010, with the images posted to the Internet by summer 2011. California Coastal LiDAR Project Report. More information here. Want data? Here's NOAA's Digital Coast Data Access Viewer.
It has been estimated that approximately 950 miles of California's 1,120 miles of coastline are actively eroding. These areas comprise 86% of the coastline.
The California Beach Restoration Study (2002) states that 72% of the coast of California consists of actively eroding sea cliffs.
According to CCC staff, less than 10 miles have no dry sand beach at high tide. About 150 miles are accreting (gaining sand) or stable.
California’s coastal erosion rates generally range from 0-42cm/year; however, specific sites can retreat at much higher rates, such as Point Año Nuevo, which retreats at an average rate of nine feet per year.
In October 2010 California's Coastal Sediment Management Workgroup released California Beach Erosion Assessment Survey 2010. Through tables, figures, and appendices, this report does the following:
Surfrider Foundation comments on the California Beach Erosion Assessment Survey can be found here.
The study, The impact of the 2009-10 El Niño Modoki on U.S. West Coast beaches, published in The American Geophysical Union's "Geophysical Research Letters" on July 9, 2011 was led by the USGS in collaboration with the Oregon Department of Geology and Mineral Industries, University of California-Santa Cruz, Washington Department of Ecology, Oregon State University and Scripps Institution of Oceanography. The authors took advantage of up to 13 years of seasonal beach survey data along 148 miles of coastline and tracked shoreline changes through a range of wave conditions. The following is from a USGS press release.
"The stormy conditions of the 2009-10 El Niño winter eroded the beaches to often unprecedented levels at sites throughout California and vulnerable sites in the Pacific Northwest," said Patrick Barnard, USGS coastal geologist. In California, for example, winter wave energy was 20 percent above average for the years dating back to 1997, resulting in shoreline erosion that exceeded the average by 36 percent, he and his colleagues found.
Among the most severe erosion was at Ocean Beach in San Francisco where the winter shoreline retreated 184 ft., 75 percent more than in a typical winter. The erosion resulted in the collapse of one lane of a major roadway and led to a $5 million emergency remediation project. In the Pacific Northwest, the regional impacts were moderate, but the southerly shift in storm tracks, typical of El Niño winters, resulted in severe local wave impacts to the north-of-harbor mouths and tidal inlets. For example, north of the entrance to Willapa Bay along the Washington coast, 345 ft. of shoreline erosion during the winter of 2009-10 destroyed a road.
One of the most recent coastal erosion studies in California is Rates and Trends of Coastal Change in California and the Regional Behavior of the Beach and Cliff System by Cheryl J. Hapke, Dave Reid, and Bruce Richmond of the U.S Geological Survey. This study was published in the Journal of Coastal Research in May 2009. The abstract reads:
The U.S. Geological Survey (USGS) recently completed an analysis of shoreline change and cliff retreat along the California coast. This is the first regional, systematic measurement of coastal change conducted for the West Coast. Long-term (120 y) and short-term (25 y) shoreline change rates were calculated for more than 750 km of coastline, and 70 year cliff-retreat rates were generated for 350 km of coast.
Results show that 40% of California’s beaches were eroding in the long term. This number increased to 66% in the short term, indicating that many beaches have shifted toward a state of chronic erosion. The statewide average net shoreline change rates for the long and short term were 0.2 m/y and -0.2 m/y, respectively. The long-term accretional signal is likely related to large coastal engineering projects in some parts of the state and to large fluxes of sediment from rivers in other areas. The cliff-retreat assessment yielded a statewide average of -0.3 m/y. It was found that Northern California has the highest overall retreat rates, which are influenced by erosion hot spots associated with large coastal landslides and slumps.
The databases established as part of the shoreline change and cliff-retreat analyses were further investigated to examine the dynamics of the beach/cliff system. A correlation analysis identified a strong relationship between the geomorphology of the coast and the behavior of the beach/cliff system. Areas of high-relief coast show negative correlations, indicating that higher rates of cliff retreat correlate with lower rates of shoreline erosion. In contrast, low to moderate-relief coasts show strong positive correlations, wherein areas of high shoreline change correspond to areas of high cliff retreat.
A September 2006 coastal beach erosion study for California is Historical Shoreline Change and Associated Coastal Land Loss Along Sandy Shorelines of the California Coast by the USGS. An important finding from the report concludes that the net shoreline change in the short-term (25-40 years) indicates that 66 percent of California´s beaches are eroding. Central California, which covers the area from Point Reyes to just north of Santa Barbara, shows the highest percentage of erosion. Long-term coastal shoreline change (using data gathered over the last 120 years) shows a trend of expansion, which is likely attributable to large scale coastal engineering and beach fill projects in Southern California, and to a high influx of sediments from coastal rivers in Northern California.
USGS also has completed a Historical Cliff Retreat assessment for California.
Littoral Cells, Sand Budgets, and Beaches: Understanding California's Shoreline by Kiki Patsch and Gary Griggs (October 2006) is a useful summary of coastal conditions in California that also contains a discussion of beach nourishment, including the nourishment history of individual littoral cells.
The USGS Internet Map Server site includes individual data layers compiled in support of the U.S. Geological Survey's National Assessment of Shoreline Change Program. Data layers include short- and long-term shoreline change evaluations, and historical and modern shorelines released via The National Assessment of Shoreline Change: A GIS Compilation of Vector Shorelines and Associated Shoreline Change Data for the Sandy Shorelines of the California Coast (OFR 2006-1251).
Average cliff retreat rates along the shores of the Monterey Bay National Marine Sanctuary range from 7 to 12 cm/yr (between 1953 and 1994). At the erosion “hotspots” area located at Opal Cliffs, Depot Hill and Manresa in Santa Cruz County the erosion rates range from 20 to 63 cm/yr. A more recent study found that erosion rates along the southern Monterey Bay shoreline between Moss Landing and Wharf II in Monterey are the highest in the State of California. Although this shoreline is not heavily developed, eight oceanfront facilities are at a high risk from erosion over the next fifty years.
The Heinz report Evaluation of Erosion Hazards states that erosion rates are approximately 1 ft/year in Santa Cruz and San Diego.
The regional summaries presented below come from Living with the California Coast. This book, published in 1985, provides excellent maps and information about coastal hazards. For Southern California, where more current information exists, the summary provided here is augmented by information from several detailed reports cited in the text.
UPDATE: For those determined to live next to California's dynamic shoreline, the new and updated book Living with the Changing California Coast should be required reading. Written by Gary Griggs, Kiki Patsch, and Lauret Savoy, with contributions from more than a dozen other coastal experts, the book was released in November 2005 from the University of California Press. It is a completely revised and updated edition of the 1985 book Living with the California Coast, by Griggs and Savoy. The first part of the book provides a wealth of background information on coastal processes and hazards, with advice for home buyers, residents, coastal managers, and developers. There are sections on climate change, rising sea levels, coastal erosion, responding to coastal hazards, and coastal policy and legislation. The second part of the book consists of 12 chapters, each providing a comprehensive discussion of one geographic section of the coast. The book includes nearly 300 photographs and 81 detailed maps covering the entire coast. The maps include hazard ratings, erosion rates where available, descriptions of coastal landforms, locations of seawalls and other types of armoring, and other useful and interesting information about every stretch of shoreline. The photographs include dramatic illustrations of damage to coastal structures, as well as extensive documentation of natural and man-made features along the coast. Many of the photos were provided by the California Coastal Records Project, which includes photographs of the entire California coastline.
Also see the excellent follow-up article, Understanding California's Shoreline (October 2006).
Northern California (Oregon Coast to San Francisco):
This stretch of coast is prone to frequent large swells and severe storms, so many areas of the coastline experience severe erosion along the shoreline, cliffs, and bluffs. Only a limited amount of erosion data exists for this area, but the data show highly variable shoreline change rates. The erosion rates vary between some spots with as much as 10 feet per year of beach loss to spots with 7 inches of accretion per year.
Central California (San Francisco to Point Conception):
This stretch of coast is also prone to frequent large surf and severe storms, and has many areas with active erosion along the beach, cliff, and bluffs. There is much more data for this area, showing that the Central California coast experiences less erosion on average than Northern California. Work by Laura Moore for the city of Santa Cruz found that the bluff line was retreating, on average, less than 1 foot per year. The erosion ranges for Santa Cruz were found to be from 0 to 63 cm/yr with and average rate of about 10 cm per year.
Southern California (Point Conception to Mexico):
Living with the California Coast provides quantitative figures for erosion in Southern California, but this information is dated compared to work noted below.
In 1993, the Los Angeles District of the Army Corps of Engineers (ACOE) published the Existing State of Orange County Coast report. The report thoroughly explains the oceanographic and geologic processes affecting the Orange County coast, and gives detailed statistics on longshore transport at their monitoring stations. The ACOE has additional data on shoreline change for other areas of Southern California. These documents are available at the ACOE district offices.
Also from 1993 is The Myth and Reality of Southern California Beaches, by Reinhold Flick of Scripps Institution of Oceanography.
In 1994, the California Department of Boating and Waterways and San Diego Association of Governments produced a report titled the Shoreline Erosion Assessment and Atlas of the San Diego Region. The report illustrates for each part of the coast from Dana Point to the Mexican Border the threats to coastal development, environmental resources, and recreational resources. The report uses risk assessments to classify the threats to the studied resources. While the report does not provide figures for shoreline change rates, higher degrees of risk are associated with greater shoreline change rates, so the high-risk areas indicate areas prone to severe erosion problems. The report also identifies sections of the coastline that have "shoreline protection" (Rip-Rap, Concrete Seawall, Timber Seawall, Sheet-Pile Seawall).
A 1999 study of coastal hazards for the Federal Emergency Management Agency (FEMA), Evaluation of Coastal Hazards, focused on two areas of California, San Diego and Santa Cruz. The research for these areas is documented in several publications. They describe specifics about the effects of El Niño on bluff erosion and the influence of geology on erosion rates. These studies measured erosion rates during the intense 1997-98 El Niño. In that winter, storm after storm battered the shore, causing bluff failures, landslides, floods, and enhanced cliff erosion. Confirming earlier studies by others, these studies showed that erosion in California occurs episodically, not at a steady pace. Although beach retreat and flooding pose a high risk to the East Coast and Gulf states, bluff collapse is the greatest threat in California. This is particularly true in counties such as San Diego and Santa Cruz, where houses have been built on unstable sea cliffs.
The beaches around the Isla Vista coast adjacent to University of California, Santa Barbara (UCSB), and Goleta Beach suffered dramatic erosion during the El Niño events of 1982-83 and 1997-98 and never fully recovered. Ongoing discussions among oceanfront property owners and Santa Barbara County are examining a variety of shoreline protection alternatives without an understanding of the long-term trends to the beaches in this area.
A study by UC Santa Cruz graduate student David Revell analyzed a historical 70-year record of beach width changes along a nine-kilometer shoreline segment from Ellwood Beach to Goleta Beach, near Isla Vista, California. Results show an oscillation in beach widths as opposed to a long term narrowing as predicted based on sand supply reductions. The oscillations of beach width correlate with different phases of the multi-decadal Pacific Decadal Oscillation (PDO) Index. During positive PDO phases of stormier and wetter conditions, beach widths narrow while during negative calmer drier phases, beach widths widen. Results also indicate significant variability in the beach widths along study area. Ellwood beach widths remained the most stable while UCSB and Goleta Beach exhibit the widest variability indicating a high capacity for sand storage. Parts of the Isla Vista, UCSB, and Goleta Beach shoreline show significant changes to beach widths, the majority of these areas (59%) correspond to shore protection structures or other human alterations. Significant effects of shore protection structures show impacts associated with passive erosion or beach drowning, and placement loss. Of all of the shore protection structures in the area, 77% of the intersecting transects exhibit significant reductions in beach width. El Niños play an important role in regulating beach widths with the narrowest beaches occurring after the major events of 1982-83 and 1997-98. The 1982-83 El Niño was the key event resulting in the largest beach width changes, especially along UCSB and Goleta Beaches. For these two shoreline segments, the overall beach area was reduced by 150,000 m2. Beach widths have never recovered to pre-1982-83 levels. Beach widths following the 1997-98 El Niño did recover to post -1982-83 levels. The volume of sand removed from the beaches during the 1982-83 event was estimated to be around 385,000 m3. From 1993-1995, a 74% increase in the Santa Barbara harbor dredge records above long-term averages provides evidence of a 1.7-km/yr (1 mi/yr) alongshore transport rate of littoral sands.
Bill McLaughlin of Surfrider Foundation's San Francisco Chapter has prepared a report A History of Coastal Erosion at Ocean Beach. This report documents both erosion and various erosion response efforts at Ocean Beach from the mid-1800s to the present. The report concludes"...the best way to solve the erosion hotspot at Sloat is through a managed retreat strategy. Managed Retreat at Sloat would be the phased pull back of infrastructure away from the ocean. With such a plan both infrastructure security and beach restoration can be attained."
Other important erosion studies include:
Beach erosion studies are being conducted in San Diego County by scientists at Southern California Coastal Ocean Observing System (SCCOOS) and Scripps Institution of Oceanography (SIO). The goal of the 2010 Cardiff Beach Erosion & Inundation Project is to develop field-validated, site-specific inundation models for use in providing real-time warnings of wave and tide-induced coastal inundation. For 2013 Beach Erosion in Southern California, ongoing monitoring is building a database of sand level changes and waves at local beaches, including an El Nino and the recent 2012 nourishment at Solana-Cardiff beaches. Beach widths were minimum in the 2010 El Nino at all sites, and maximum at sites nourished in Fall 2012. Monitoring is ongoing and beach widths are updated approximately monthly.
There is a USGS website titled Coastal Erosion Along the U.S. West Coast During the 1997-98 El Niño: Expectations and Observations.
As referenced above, an exciting development in documenting coastal conditions and tracking coastal erosion, coastal structures, and other changes in the shoreline is the California Coastal Records Project. This project was initiated and carried out by Kenneth and Gabrielle Adelman, who in 2002 flew the entire California coast and took detailed low-level photographs. Since then, historical photos from 1972, 1979, 1987 and 1989 have been added to enable time comparisons. Finally, the coast was flown and photographed again in 2005 and subsequent years.
The California Coastal Commission created the Beach Erosion and Response (BEAR) Guidance Document in December of 1999. This report provides assistance to both applicants and reviewers of coastal protection projects. There are succinct and informative descriptions of coastal environments and protection strategies, the requirements for filing an application, and detailed information about how the staff of the Coastal Commission handles applications for such projects as seawalls, revetments, upper bluff protection and beach fill. This document is now available by request from the California Coastal Commission. To receive a copy, call the Technical Services Unit in the Headquarters Office (415-904-5240).
The Ocean Resources Management Program of the Resources Agency of California prepared a Draft Policy On Coastal Erosion Planning And Response in 2001. This document was intended to update the original 1978 Shoreline Erosion Policy. After receiving and incorporating extensive comments on the first draft, a second draft, titled Draft Review of California Coastal Erosion Planning and Response: A Strategy for Action was released for public comment in March 2003. It does not seem to be currently available online.
The State of California is working with the U.S. Army Corps of Engineers (USACE), representatives of local governments, and other stakeholders to develop a California Coastal Sediment Management Master Plan (SMP) to systematically evaluate coastal erosion and beach loss needs. On a regional basis, the plan will focus on the inter-relationships between beaches, wetlands, ports, and flood control facilities to determine how to maximize approaches to managing coastal sediments and reducing beach losses. One vehicle available to help meet the challenges of developing a Master plan, and to address coastal erosion issues in general, is the California Coastal Sediment Management Workgroup (CSMW), a statewide effort initiated by both the USACE and the California Resources Agency in late 1999. The group's goal is to facilitate regional approaches to protecting, enhancing and restoring California's coastal beaches and watersheds through federal, state and local cooperative efforts. The SMP purposes include reducing shoreline erosion and coastal storm damages, providing for environmental restoration and increasing natural sediment supply to the coast, restoring and preserving beaches, and improving water quality along beaches. The SMP encourages alternative to shoreline protection structures, such as beach nourishment projects, sand bypassing projects and dam removal projects. The CSMW maintains a website through the state Department of Boating and Waterways and holds public workshops to discuss issues of concern.
The Southern California Coastal Water Research Project (SCCWRP) in its 2001-2002 work plan reports on a joint effort between SCCWRP and the US Geological Survey's Marine and Coastal Division - Assessment Of Shoreline Change In The Southern California Bight:
Wide sandy beaches provide a natural buffer against coastal hazards such as storms, wave action that may undermine cliffs and bluffs, and more long-term impacts such as sea level rise. Wide sandy beaches are also a draw for tourism and recreation. The loss of sandy beaches translates to an increase in hazard for coastal development and its residents as well as the loss of recreation and tourism revenue. Despite the critical nature of erosion, specific information about the hazards of erosion and what is being done to manage it is lacking. The goal of this project is to assess the condition of the shoreline in Southern California and the extent of the erosion hazard, both long and short-term.
Year one of this three-year project will consist of data collection and assessment. Year two will focus on assessing short-term erosion due to storms, such as El Niño. Year three will focus on assessing long-term erosion in the Southern California Bight.
A ground survey of the coastal zone within the Southern California Bight will be conducted to identify coastal type, such as rocky, sandy, vegetated or armored, and structures, such as seawalls, jetties, groins, breakwaters, and piers. This inventory will be used as baseline data for the current condition of the shoreline, and will be compared with a 1977 inventory completed by the Department of Navigation and Ocean Development to assess how coastal management and response to shoreline change has evolved over the last 20 years.
Available erosion data will be compiled in a database in order to assess data gaps and methodologies. Numerous methods have been employed to determine erosion rates, but it is still unclear as to how accurate and comparable these methods are, making it difficult to compile local erosion data into a regional synthesis. A goal for the second year of this project is to determine whether the methods employed are accurate and what differing methods, if any, can be combined to establish a regional assessment of shoreline erosion.
CCC staff note that California beaches have had a lot of fill from dredging of harbors, construction projects, etc. California has also had sediment declines from sand mining, flood control structures, dams, etc. Both factors greatly obscure natural signals of beach conditions.
Another useful source of information is the website of the Coastal Morphology Group at Scripps Institute of Oceanography. This site contains links to research papers on coastal erosion, sediment budgets, littoral cells, climate change, and more. See Living With Coastal Change.
The Heinz Center's Evaluation of Erosion Hazards, that is referenced below notes that The El Niño winter of 1982-1983 set the stage for severe storm-induced erosion damage to structures along the California coast. It caused over $100 million in coastal property damages, including the loss of 33 oceanfront homes, damage to 300 more houses and 900 businesses, and $35 million in losses to coastal public recreational infrastructure (Flick, 1998). The 1997-1998 El Niño again caused extensive erosion of Pacific Coast beaches and left many cliff-top buildings increasingly exposed to storm- and erosion-related losses.
California Sea Grant is another source of information on coastal erosion in California. Their website includes a summary of work by Gary Griggs, director of the Institute of Marine Sciences at the University of California at Santa Cruz, and others noted above.
The Heinz Center's Evaluation of Erosion Hazards, conducted for the Federal Emergency Management Agency (FEMA), studied the causes of coastal erosion hazards and proposed a variety of national and regional responses. The study, published in April 2000, concentrates on the economic impacts of erosion response policies as well as the cost of erosion itself to homeowners, businesses, and governmental entities.
A NOAA website that has graphs of sea level data for many coastal locations around the country over the last 40 to 50 years and projections into the future is Sea Levels Online.
NOAA Shoreline Website is a comprehensive guide to national shoreline data and terms and is the first site to allow vector shoreline data from NOAA and other federal agencies to be conveniently accessed and compared in one place. Supporting context is also included via frequently asked questions, common uses of shoreline data, shoreline terms, and references. Many NOAA branches and offices have a stake in developing shoreline data, but this is the first-ever NOAA Website to provide access to all NOAA shorelines, plus data from other federal agencies. The site is a culmination of efforts of NOAA and several offices within NOS (including NOAA’s Coastal Services Center, National Geodetic Survey, Office of Coast Survey, Special Projects Office, and Office of Ocean and Coastal Resource Management) and other federal agencies to provide coastal resource managers with accurate and useful shoreline data.
A related site launched in 2008 is NOAA Coastal Services Center's Digital Coast, which can be used to address timely coastal issues, including land use, coastal conservation, hazards, marine spatial planning, and climate change. One of the goals behind the creation of the Digital Coast was to unify groups that might not otherwise work together. This partnership network is building not only a website, but also a strong collaboration of coastal professionals intent on addressing coastal resource management needs. Website content is provided by numerous organizations, but all must meet the site’s quality and applicability standards. More recently, NOAA Coastal Services Center has developed a Sea Level Rise and Coastal Flooding Impacts Viewer as part of its Digital Coast website. Being able to visualize potential impacts from sea level rise is a powerful teaching and planning tool, and the Sea Level Rise Viewer brings this capability to coastal communities. A slider bar is used to show how various levels of sea level rise will impact coastal communities. Completed areas include Mississippi, Alabama, Texas, Florida, and Georgia, with additional coastal counties to be added in the near future. Visuals and the accompanying data and information cover sea level rise inundation, uncertainty, flood frequency, marsh impacts, and socioeconomics.
California Coastal Commission
45 Fremont Street, Suite 2000
San Francisco, CA 94105
California Coastal Commission
45 Fremont Street, Suite 2000
San Francisco, CA 94105
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