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Author: Andre Doria Publisher: ISBN: Category : Languages : en Pages : 102
Book Description
Repeated aerial and ground-based observations that measured seasonal beach sand level changes along 195 km of coastline for up to 16 years were used to characterize and model Southern California beach sand level changes. A wave buoy network initialized a spectral refraction wave model that provided nearshore (~10 m depth) hourly wave estimates every ~100 m alongshore throughout the entire study region. Localized and regional biannual ground-based surveys captured seasonal subaerial beach profile changes across San Diego County, as well as the associated bathymetry changes not detected by aerial methods. Volume changes along the surveyed bathymetry transects varied seasonally owing to fluctuations in the incident wave energy. Comparative analysis of the volume changes along the beach profiles demonstrated estimating the fraction of subaqueous volume change based exclusively on subaerial observations is highly variable with a reduction in the total volume change captured by the subaerial observations particularly during periods of excessive erosion. Notably, the link between near-shore the displaced beach face sand volume (e.g. both subaerial and bathymetric profile components) and that of the subaerial beach is obscure. Observations at five focus sites in San Diego County characterized short-term and long-term shoreline changes and waves, including the impacts of two significant El Niño winters, from 1997 through 2013. An existing wave-driven shoreline model accurately predicted shoreline fluctuations during years of normative wave and beach conditions, but over-predicted erosion during remarkable erosion events such as El Niño. Modifications to the model formulation account for erosion resistant features such as non-erodible seawall back beaches or durable strata (e.g. cobbles) exposed during severe erosion. This improved the model skill (i.e. data to model correlation R2) during highly erosive wave events. High spatial resolution biannual aerial lidar surveys captured regional beach sand level changes spanning the entire 195-km study region. Alongshore variations in both waves and beach sand levels were notable with distinct large-scale differences occurring between the northern and southern halves of the study site. Additional ground-based data were used conjointly with the aerial observations to tune a regional shoreline model spanning 90 km of San Diego County coast.
Author: Andre Doria Publisher: ISBN: Category : Languages : en Pages : 102
Book Description
Repeated aerial and ground-based observations that measured seasonal beach sand level changes along 195 km of coastline for up to 16 years were used to characterize and model Southern California beach sand level changes. A wave buoy network initialized a spectral refraction wave model that provided nearshore (~10 m depth) hourly wave estimates every ~100 m alongshore throughout the entire study region. Localized and regional biannual ground-based surveys captured seasonal subaerial beach profile changes across San Diego County, as well as the associated bathymetry changes not detected by aerial methods. Volume changes along the surveyed bathymetry transects varied seasonally owing to fluctuations in the incident wave energy. Comparative analysis of the volume changes along the beach profiles demonstrated estimating the fraction of subaqueous volume change based exclusively on subaerial observations is highly variable with a reduction in the total volume change captured by the subaerial observations particularly during periods of excessive erosion. Notably, the link between near-shore the displaced beach face sand volume (e.g. both subaerial and bathymetric profile components) and that of the subaerial beach is obscure. Observations at five focus sites in San Diego County characterized short-term and long-term shoreline changes and waves, including the impacts of two significant El Niño winters, from 1997 through 2013. An existing wave-driven shoreline model accurately predicted shoreline fluctuations during years of normative wave and beach conditions, but over-predicted erosion during remarkable erosion events such as El Niño. Modifications to the model formulation account for erosion resistant features such as non-erodible seawall back beaches or durable strata (e.g. cobbles) exposed during severe erosion. This improved the model skill (i.e. data to model correlation R2) during highly erosive wave events. High spatial resolution biannual aerial lidar surveys captured regional beach sand level changes spanning the entire 195-km study region. Alongshore variations in both waves and beach sand levels were notable with distinct large-scale differences occurring between the northern and southern halves of the study site. Additional ground-based data were used conjointly with the aerial observations to tune a regional shoreline model spanning 90 km of San Diego County coast.
Author: Marissa L. Yates Publisher: ISBN: Category : Languages : en Pages : 133
Book Description
Seasonal airborne and ground-based observations of sand level changes were made along the coast of southern California from 2001 to 2008. Hourly, high alongshore spatial resolution wave estimates from a network of wave buoys and a spectral refraction wave model complement the sand level change data. Water returns from the ocean surface were removed from the airborne lidar elevation observations with a new method using tide and wave data, which was validated with concurrent in situ surveys. The resultant sand levels show high alongshore variability in seasonal shoreline position change along the 120-km survey region. Alongshore variability in wave energy, geologic factors, and sand grain size are hypothesized to control the alongshore variability of the seasonal shoreline change magnitude. Monthly or more frequent ground-based surveys at four selected focus sites show seasonal shoreline and bathymetry change, with winter shoreline erosion and offshore bar development, and summer shoreline accretion and the loss of the offshore bar. Analysis of surveys completed after a small beach nourishment at Torrey Pines Beach showed the presence of the nourishment through more than one full seasonal cycle. Observations from Torrey Pines Beach show the dependence of shoreline change on the initial shoreline position and the wave forcing. The observations motivated the development of an equilibrium shoreline change model, which accurately reproduces the observations with four free parameters. With at least two years of monthly surveys or multiple years of appropriately-timed biannual observations used to determine the free parameters, the model accurately predicts withheld observations and is applied at the additional survey sites. Ongoing work includes applying the model at additional locations and investigating the relationship between the tuned parameters and geologic factors.
Author: Bonnie Cecily Ludka Publisher: ISBN: Category : Languages : en Pages : 135
Book Description
Sand levels were monitored at five southern California beaches for periods of 3 to 15 years, spanning a total of 18 km alongshore. Every 3 months, GPS equipped vehicles measured sand elevations on cross-shore transects from the backbeach to 8 m depth, with 100 m alongshore resolution. Subaerial observations were collected monthly above the spring low-tide line. Wave buoys and a numerical model provided hourly wave estimates in 10 m depth at each site. These observations show that beach profile shapes (depth versus cross-shore distance) evolve consistent with the equilibrium hypothesis: under steady wave conditions, evolution is toward a unique, wave condition dependent, equilibrium beach profile. Beaches far out of equilibrium change rapidly, and as equilibrium is approached they change ever more slowly. At the sandy regions, a simple equilibrium beach state model has skill >0.5 (Chapter 2, [Ludka et al., 2015]). Repeated nourishments over multiple decades, costing hundreds of thousands of dollars, are a primary beach management strategy worldwide, but the wave-driven redistribution of nourishment sand is poorly understood. At four survey sites, 50,000-300,000 m^3 of imported sand was placed on the subaerial beach over alongshore spans between 300-1300 m. Wave conditions in the months after placement were similar at all sites, but the subaerial nourishment pads eroded and retreated landward at different rates. A pad built with native-sized sand washed offshore in the first few storms. In contrast, nourishments with coarser than native sand remained on the beach face for several years and protected shorelines during the significant wave attack of the 2015-16 El Niño (Chapter 3, [Ludka et al., 2016]). These relatively resilient and coarse subaerial pads stretched alongshore in a pattern consistent with seasonally shifting, wave-driven alongshore currents. Natural gains and losses in the total sand volume budget, integrated spatially over each site, are sometimes larger than the nourishment contributions (Chapter 4, in prep for Coastal Engineering).
Author: National Research Council Publisher: National Academies Press ISBN: 0309255945 Category : Science Languages : en Pages : 274
Book Description
Tide gauges show that global sea level has risen about 7 inches during the 20th century, and recent satellite data show that the rate of sea-level rise is accelerating. As Earth warms, sea levels are rising mainly because ocean water expands as it warms; and water from melting glaciers and ice sheets is flowing into the ocean. Sea-level rise poses enormous risks to the valuable infrastructure, development, and wetlands that line much of the 1,600 mile shoreline of California, Oregon, and Washington. As those states seek to incorporate projections of sea-level rise into coastal planning, they asked the National Research Council to make independent projections of sea-level rise along their coasts for the years 2030, 2050, and 2100, taking into account regional factors that affect sea level. Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future explains that sea level along the U.S. west coast is affected by a number of factors. These include: climate patterns such as the El Niño, effects from the melting of modern and ancient ice sheets, and geologic processes, such as plate tectonics. Regional projections for California, Oregon, and Washington show a sharp distinction at Cape Mendocino in northern California. South of that point, sea-level rise is expected to be very close to global projections. However, projections are lower north of Cape Mendocino because the land is being pushed upward as the ocean plate moves under the continental plate along the Cascadia Subduction Zone. However, an earthquake magnitude 8 or larger, which occurs in the region every few hundred to 1,000 years, would cause the land to drop and sea level to suddenly rise.
Author: Gary Bruce Griggs Publisher: Univ of California Press ISBN: 0520938674 Category : Nature Languages : en Pages : 553
Book Description
Crowded into the beautiful, narrow strip at the edge of the ocean, the large number of people who live near California's dynamic coastline often have little awareness of the hazards—waves, tides, wind, storms, rain, and runoff—that erode and impact the coast and claim property on a regular basis. This up-to-date, authoritative, and easy-to-use book, a geological profile of the California coast from Mexico to the Oregon border, describes the landforms and processes that shape the coastline and beaches, documents how erosion has affected development, and discusses the options that are available for dealing with coastal hazards and geologic instability. A completely revised and updated edition of Living with the California Coast (1985), this book features hundreds of new photographs and the latest data on human activity on the coast, on climate change, on rising seas levels, and on coastal erosion and protection. With its dramatic photographs and mile-by-mile maps, Living with the Changing California Coast will be an essential resource for those intending to buy or build along the coast, those who need specific information about various coastal regions, and those who are seeking information about how this remarkable coastline has evolved. *279 photographs portray natural coastal features and processes and illustrate many instances of what can happen to buildings on the coast *81 maps, covering the entire coast, detail types of coastal landforms, coastline erosion rates, locations of seawalls or armor, and other specific areas of interest *Offers specific advice for homebuyers,residents, and developers on which areas to avoid, on what safety measures should be taken, and on what danger signals should be heeded
Author: John C. Harlett Publisher: ISBN: Category : Beach erosion Languages : en Pages : 120
Book Description
Beach-elevation measurements were made and sand samples were collected along a single profile daily at low tide during the period from February 1 through March 31, 1967. Wave and tide data were recorded continuously. The beach, composed of medium-to-fine quartz and feldspar sand, is well sheltered from wave action. Wave steepness exerts a great influence on the beach profile. An equilibrium profile was found to exist for a given wave steepness. As wave conditions change, the beach profile tends to change toward the equilibrium profile associated with the new wave steepness. Given an initial beach profile, the amounts of cut and fill that will occur with a given change in wave steepness can be predicted. Textural parameters do not appear to be related to changing wave conditions in a simple way. Equilibrium values of mean grain size, sorting, skewness, and kurtosis exist for any given location on the beach profile. The equilibrium values are apparently indepdent of wave conditions. (Author).
Author: Andre Doria
Author: Andre Doria
Author: Marissa L. Yates
Author: Bonnie Cecily Ludka
Author: Charles E. Nordstrom
Author: National Research Council
Author: United States. Beach Erosion Board
Author: Douglas Lamar Inman
Author: Gary Bruce Griggs
Author: John C. Harlett
Author: Rafael Almar