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Coastal and Other Hazards (Se) Goleta General Plan /Coastal Land Use Plan 5.0 Safety Element CHAPTER 5.0 SAFETY ELEMENT: COASTAL AND OTHER HAZARDS (SE) 5.1 INTRODUCTION General Plan Law Requirements [GP] The Safety Element is one of seven general Safety Element Policies plan elements mandated by state law. The SE 1: Safety in General scope of the Safety Element is specified in SE 2: Bluff Erosion and Retreat Section 65302 (g) of the California SE 3: Beach Erosion and Shoreline Hazards SE 4: Seismic and Seismically Induced Hazards Government Code as follows: SE 5: Soil and Slope Stability Hazards SE 6: Flood Hazards The general plan shall include a safety SE 7: Urban and Wildland Fire Hazards element for the protection of the SE 8: Oil and Gas Industry Hazards community from any unreasonable SE 9: Airport-Related Hazards. SE 10: Hazardous Materials and Facilities risks associated with the effects of SE 11: Emergency Preparedness seismically induced surface rupture, ground shaking, ground failure, tsunami, seiche, and dam failure; slope instability leading to mudslides and landslides; subsidence and other geologic hazards known to the legislative body; flooding; and wild land and urban fires. The safety element shall include mapping of known seismic and other geologic hazards. It shall also address evacuation routes, peak-load water supply requirements, and minimum road widths and clearances around structures, as those items relate to identified fire and geologic hazards. Coastal hazards such as bluff retreat and shoreline erosion are also addressed in this element, as are hazards associated with oil and gas production, processing, and transport. California Coastal Act Requirements [CP] The California Coastal Act (Coastal Act) requires new development to be sited and designed to minimize risks, ensure stability and structural integrity, and neither create nor contribute significantly to erosion or require the construction of new shoreline protective devices that would substantially alter natural landforms along coastal bluffs and cliffs. Section 30235 of the Public Resources Code allows the construction of shoreline protective devices where existing development is threatened by erosion and when designed to eliminate or mitigate impacts on shoreline sand supply. The Coastal Act provides that development damaged or destroyed by natural disaster can be rebuilt in the same location and is exempt from the requirements for a coastal development permit under certain circumstances. It also provides standards for oil and gas development in the Coastal Zone. Appropriate oil spill prevention and response measures are required, and a number of policies require adverse environmental impacts to be minimized. Coastal, Geological, and Other Hazards: 2005 [GP/CP] Coastal, geological, industrial, and other hazards known to occur within Goleta include the following: • Coastal hazards such as bluff erosion and retreat, beach erosion, and exposure of pier remnants and other shoreline hazards. September 2006 5-1 Goleta General Plan /Coastal Land Use Plan 5.0 Safety Element • Seismically induced hazards such as ground shaking, surface rupture, liquefaction, and tsunamis. • Soil- and slope-related hazards such as expansive soils, compressible and collapsible soils, landslides, and rock-falls. • Flood hazards. • Urban and wildland fire hazards. • Oil and gas production, processing, and transportation hazards, including remnants from previous operations. • Hazards associated with aircraft operations at the Santa Barbara Municipal Airport. • Storage, handling, and transportation of hazardous materials. • Public safety concerns such as crime prevention/reduction. • Emergency preparedness. Coastal Hazards Bluff Erosion and Retreat: Much of Goleta’s coastline is characterized by sea cliffs and coastal bluffs, with typical heights of 50 to 70 feet. Sea cliffs are susceptible to periodic failure and erosion when wave action undermines the toe of the cliff. This sea cliff retreat occurs episodically, with a lateral loss of several feet or tens of feet resulting from a single collapse, followed by years of relative stability. Average cliff retreat rates are primarily dependent on oceanographic exposure and cliff composition, with certain Coastal Bluff at Ellwood Mesa types of rocks and sediments more resistant to weathering and erosion than others. Surface drainage and saturated soils also contribute to bluff failure. Shoreline change studies have documented average, long-term rates of sea cliff retreat of 0.45 to 0.62 foot per year for the Ellwood Mesa area (Hoover & Associates 1998), and rates of 0.3 to 1.3 feet per year for the cliffs along Isla Vista to the east of Goleta’s coastline (Sylvester 2005). Areas subject to cliff retreat are among the areas depicted as having a high landslide potential on Figure 5-1. Beach Erosion and Other Shoreline Hazards: Beaches and shoreline areas are dynamic features that continually adjust to changing oceanography and climatic conditions. Beaches will erode—laterally in the form of shoreline retreat, and vertically by deflation or scour—during high-wave events such as storms and also in response to seasonal changes in wave characteristics. Heavy surf seasons associated with the El Niño storms in 1982 to 1983 and 1997 to 1998 resulted in considerable beach erosion and the complete loss of bluff-fronting dunes, although much of Goleta’s coastline has recovered since that time. In general, beaches in southern Santa Barbara County tend to be wider and have higher elevations during the summer, and narrower and lower during the winter. Beach scour, or vertical beach erosion, can expose previously buried hazards, such as remnants of piers and oil and gas wells. While attempts to remove these structures were made at the time of their demolition or abandonment, removal often consisted of mechanically cutting September 2006 5-2 Goleta General Plan /Coastal Land Use Plan 5.0 Safety Element pilings and caissons at some level (1 to 3 feet, typically) below the sand level. Removal down to bedrock was rarely achieved, and subsequent beach erosion and scour periodically has exposed these remnants. As these remnants are usually iron or concrete and can be partially or fully submerged, they pose a hazard to beach users, swimmers, and surfers. Seismic and Seismically Induced Hazards Ground Shaking: Goleta, like much of California, is in an area prone to earthquakes. In general, the closer an earthquake’s epicenter and the larger the magnitude of the event, the higher the likelihood of strong ground shaking. California Building Code requirements set forth the minimum design and construction standards for structures to resist seismic forces. Nevertheless, strong ground shaking can crack the foundation and walls of buildings, damage roads, power lines, pipelines, and other infrastructure, and cause injuries and deaths. Un- reinforced brick masonry structures are particularly susceptible to damage or collapse. Surface Rupture: A fault surface rupture is The Alquist-Priolo Earthquake Fault Zoning Act the displacement or splitting of the ground was passed in 1972 to mitigate the hazard of surface along the trace of a fault in association with faulting to structures for human occupancy. The Act's an earthquake. Such a surface rupture could main purpose is to prevent the construction of buildings used for human occupancy on the surface damage buildings, streets, pipelines, or other trace of active faults. structures. Surface rupture or displacement along city streets and highways can interfere with traffic flow and present constraints on emergency access. Faults near or within Goleta include the More Ranch Fault, the Glen Annie Fault, and the Carneros Fault (see Figure 5-1). None of these faults are classified as active by the State Division of Mines and Geology or subject to an Alquist-Priolo Special Studies Zone. However, according to the Santa Barbara County Seismic Safety and Safety Element (SSSE), the More Ranch Fault is considered active based on the existence of a geologically recent fault scarp (County of Santa Barbara 1991). Liquefaction and Seismic Settlement: Liquefaction is the sudden loss of soil strength due to a rapid increase in soil pore water pressures resulting from ground shaking during an earthquake. Seismic settlement is the reduction of volume within a saturated or unsaturated soil mass due to ground shaking during a seismic event. Seismic settlement may occur simultaneously or independent of liquefaction. Either of these events can result in the severe damage to building foundations and in slope failure. The areas most vulnerable to liquefaction and seismic settlement are underlain by younger alluvium where groundwater and granular sediments are both present. These areas include low-lying lands adjacent to rivers, creeks, beaches, and estuaries. The current California Building Code requires that the potential for liquefaction be assessed for the design of all structures. Tsunami: Tsunamis impinging upon land can reach heights of 50 to 100 feet in some areas of the world, although a wave of this size would not be expected to occur in the Goleta area. Tsunami run-up and the extent of inland flooding depend on the individual triggering event, the orientation of the coast, offshore bathymetry, and onshore topography. In general, low-lying shoreline areas, and areas adjacent to sloughs and coastal streams, are most susceptible to tsunami hazards. Areas subject to potential tsunami run-up are depicted schematically on Figure 5-2. Santa Barbara County’s
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