SEPTEMBER 2018 2018-R-07 The Ins�tute for Water Resources (IWR) is a U.S. Army Corps of Engineers (USACE) Field Opera�ng Ac�vity located within the Washington DC Na�onal Capital Region (NCR), in Alexandria, Virginia and with satellite centers in New Orleans, LA; Davis, CA; Denver, CO; and Pitsburg, PA. IWR was created in 1969 to analyze and an�cipate changing water resources management condi�ons, and to develop planning methods and analy�cal tools to address economic, social, ins�tu�onal, and environmental needs in water resources planning and policy. Since its incep�on, IWR has been a leader in the development of strategies and tools for planning and execu�ng the USACE water resources planning and water management programs. IWR strives to improve the performance of the USACE water resources program by examining water resources problems and offering prac�cal solu�ons through a wide variety of technology transfer mechanisms. In addi�on to hos�ng and leading USACE par�cipa�on in na�onal forums, these include the produc�on of white papers, reports, workshops, training courses, guidance and manuals of prac�ce; the development of new planning, socio-economic, and risk-based decision-support methodologies, improved hydrologic engineering methods and so�ware tools; and the management of na�onal waterborne commerce sta�s�cs and other Civil Works informa�on systems. IWR serves as the USACE exper�se center for integrated water resources planning and management; hydrologic engineering; collabora�ve planning and environmental conflict resolu�on; and waterborne commerce data and marine transporta�on systems. The Ins�tute’s Hydrologic Engineering Center (HEC), located in Davis, CA specializes in the development, documenta�on, training, and applica�on of hydrologic engineering and hydrologic models. IWR’s Naviga�on and Civil Works Decision Support Center (NDC) and its Waterborne Commerce Sta�s�cal Center (WCSC) in New Orleans, LA, is the Corps data collec�on organiza�on for waterborne commerce, vessel characteris�cs, port facili�es, dredging informa�on, and informa�on on naviga�on locks. IWR’s Risk Management Center is a center of exper�se whose mission is to manage and assess risks for dams and levee systems across USACE, to support dam and levee safety ac�vi�es throughout USACE, and to develop policies, methods, tools, and systems to enhance those ac�vi�es. Other enterprise centers at the Ins�tute’s NCR office include the Interna�onal Center for Integrated Water Resources Management (ICIWaRM), under the auspices of UNESCO, which is a distributed, intergovernmental center established in partnership with various Universi�es and non-Government organiza�ons; and the Conflict Resolu�on and Public Par�cipa�on Center of Exper�se, which includes a focus on both the processes associated with conflict resolu�on and the integra�on of public par�cipa�on techniques with decision support and technical modeling. The Ins�tute plays a prominent role within a number of the USACE technical Communi�es of Prac�ce (CoP), including the Economics CoP. The Corps Chief Economist is resident at the Ins�tute, along with a cri�cal mass of economists, sociologists, and geographers specializing in water and natural resources investment decision support analysis and mul�-criteria tradeoff techniques. The Director of IWR is Dr. Joe D. Manous, Jr., who can be contacted at: [email protected]. Addi�onal informa�on on IWR can be found at: http://www.iwr.usace.army.mil. IWR’s NCR mailing address is: U.S. Army Engineer Ins�tute for Water Resources 7701 Telegraph Road, 2nd Floor Casey Building Alexandria, VA 22315-3868 California Regional Assessment National Shoreline Management Study 2018-R-07 September 2018 Rachel Grandpre U.S. Army Corps of Engineers Institute of Water Resources, Fort Belvoir, Virginia Craig Vogt Craig Vogt, Inc., Ocean & Coastal Environmental Consultants Hacks Neck, Virginia Greg Frey CSRA Portland, Oregon Martina McPherson Arleen O’Donnell Eastern Research Group Lexington, Massachusetts Photos on cover: Top Left: Terraces North of Santa Cruz. (Source: Wikimedia Commons) Bottom Left: Rock revetment at San Clemente Beach in Orange County, California. (Source: Rachel Grandpre) Right Side: Map of California showing the 25 major littoral cells along the coast and the approximate direction of littoral transport. (Source: Developed from California Department of Navigation and Ocean Development 1977) CALIFORNIA REGIONAL ASSESSMENT NATIONAL SHORELINE MANAGEMENT STUDY ABSTRACT Much of the California shoreline is eroding. The width of the continental shelf since the ice age ended 18,000 to 21,000 years ago demonstrates the extent of erosion. Coastal sediment is in a constant state of flux because of natural forces from wind and waves; these forces continually wear away (erode) and sometimes build up (accrete) coastal land features. The natural erosion and accretion process provided California with healthy beaches, most of which were naturally narrow along coastal bluffs and cliffs, and with vibrant marshes and wetlands. Sand and sediment were being delivered to the shoreline from rivers and eroding cliffs and bluffs, which retreated unimpeded over time. This situation changed dramatically once people built homes, commercial and industrial facilities, roads, railroads, and infrastructure along the shoreline. Beaches and tourism became a major economic force. To meet the needs of beach users, many beaches were artificially widened, and structures (e.g., groins) built to protect those beaches. Dams were built for flood control, and water supply and sediment collection basins built to reduce sediment runoff. Cliffs and bluffs were armored to protect against erosion. Jetties and breakwaters were built to protect harbors and promote navigation. Rivers were channelized, or even concreted, and navigation channels were created that serve as major sediment traps. Studies conducted of beach-width and bluff-location show that approximately 40 percent of California beaches eroded in the early to late 1900s, increasing to 66 percent over the past 25 years. In general, relatively natural beaches have eroded less than beaches influenced by hard and soft engineering projects. This especially applies to beaches in Southern California. The common perception is that beaches are eroding. However, most beaches unaffected by such structures as groins or breakwaters appear to be fairly healthy when evaluated over long time frames (e.g., decades). The wide beaches that have been created by nourishment and stabilized by structures will, in time, retreat as reduced rates of nourishment take place. Since the 1930s, an average of 1.3 million cubic yards per year of sand was placed to widen narrow beaches in Southern California, but rates of nourishment have decreased over the past 20 to 30 years. These beaches face net sand losses over the coming decades, without continuing nourishment and stabilization efforts. While these beaches may be eroding back to their pre-nourishment widths, the reality for beachgoers is that wide beaches are eroding. In addition, even the 10 percent of the shoreline that has been armored is experiencing passive beach erosion. Reduced sand supply in the littoral system plays a role in beach erosion. Hardened shorelines have reduced the availability of sand and sediments from eroding cliffs and bluffs that were a source of material for natural beaches. Construction of dams and reservoirs has reduced sediment delivered to the coastal waters by an overall amount of about 25 percent, and in Southern California that level approaches 50 percent. The primary cause of erosion is wave energy, and the single most important factor producing erosion and shoreline change is the occurrence of large waves during high tides. These are influenced by such factors as individual storms, episodic El Niños, or the long-term Pacific Decadal Oscillation. At risk from the erosion of beaches, cliffs, and bluffs, as well as marshes and wetlands, are billions of dollars in real estate and commercial properties, roads and railroads, the tourism industry, commercial U.S. Army Corps of Engineers i Institute for Water Resources CALIFORNIA REGIONAL ASSESSMENT NATIONAL SHORELINE MANAGEMENT STUDY and recreational fishing, and habitat for fish and wildlife. In the context of rising sea levels, climate change with potentially increased storminess, and the knowledge that widened and protected beaches will continue to require periodic re-nourishment, short- and long-term strategies addressing the political, social, economic, and environmental implications of shoreline management are essential. This report provides an assessment of coastal change in California; the social, economic, and environmental implications of erosion of the California shoreline; and the response to these issues at federal, state, and local levels. The USACE National Shoreline Management Study Authority (PL 106-53) offers an opportunity to better understand the extent and causes of sediment movement (resulting in part from sea level rise and land subsidence), its impact on the economy and environment, as well as current sediment management practices and investments being made at all levels of government. The authority also includes several elements which suggest a broader context be considered. Specifically, this authority looks to understand the condition of US coastlines through the development of a report “…on the state of the shores of the United States…” which is to include “…economic and environmental effects caused by erosion…” and a “…description of resources committed by Federal, State, and local governments to restore and renourish shores.” Importantly it also authorizes the USACE to develop recommendations regarding “…appropriate levels of Federal and non-Federal participation in shore protection” and the “…use of a systems approach to sand management”. In short, this authority provides the USACE an opportunity to focus on sediment management within a broader coastal management context." Authors’ Note: This report primarily uses the units of measurement that were reported in the references used to develop the report text (i.e., inches, feet, miles).