Temperate Regions Projects
   

REGIONAL COASTAL ENGINEERING STUDIES – ORANGE COUNTY, CA
 

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Client:  U.S. Army Corps of Engineers, Los Angeles District
 
Since the 1940s, the northern portion of Orange County, California has been extensively modified by human activities that include harbor construction, river mouth stabilization, and the provision of more than 10 million cubic yards of beach nourishment.  Coastal Frontiers was selected to undertake a wide-ranging study of coastal processes in this region in support of the U.S. Army Corps of Engineers' Coast of California Storm and Tidal Waves Study - Orange County.

Specific study tasks were as follows:
 
Study Tasks
 
Summarize wind and current data applicable to the nearshore region
 
Conduct a fluorescent tracer study of sediment movement in the Laguna Beach pocket beaches
 
Analyze sediment input to the littoral zone from both major and minor fluvial sources
 
Evaluate historical bathymetric changes, including a detailed consideration of subsidence induced by petroleum withdrawal
 
Evaluate littoral sediment losses at Newport Submarine Canyon
 
Prepare preliminary and final budgets of sediment for the Seal Beach Littoral Cell, the Huntington Beach Littoral Cell, and the Laguna Beach Mini-Cells
 
Evaluate historical beach volume and shoreline changes, including a detailed consideration of the effects of beach nourishment at Surfside-Sunset and West Newport
 
A key breakthrough resulted from the application of a statistically-derived depth of closure to the bathymetric survey data obtained during the past six decades.  Once this technique was implemented, it became possible to track the increase in the volume of shorezone sediment that resulted from the periodic nourishment activities.

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BEACH MANAGEMENT - LONG BEACH, CA
 

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Client: City of Long Beach, California
 
The City of Long Beach waterfront combines industrial harbors, small craft marinas, and recreational beaches.  Despite the sheltering effect of the Long Beach Harbor Breakwater, localized areas have experienced chronic beach erosion.  Coastal Frontiers has supported the City's efforts to maintain its beaches through a variety of activities ranging from technical analyses to interactive meetings with interested citizen groups and city officials.  The primary study tasks and several key findings are summarized below.
 
Study Tasks
 
Assess local wave, current and water level conditions
 
Supplement quantitative findings with anecdotal evidence acquired from historical photos, maps, news accounts, and interviews with knowledgeable local residents
 
Evaluate the causes of recurring beach erosion
 
Develop and evaluate candidate mitigative measures that include bulkheads, revetments, groins, breakwater extensions, periodic beach nourishment, and sand backpassing
 
Perform a moveable-bed physical model study to evaluate a "perched beach" shore protection concept
 
Key Findings
 
Periodic sand backpassing represents a cost-effective means of maintaining the protective capacity of Peninsula Beach due to a favorable combination of source proximity and accessibility. Land scrapers are capable of moving 100,000 cubic yards per year at a cost of less than $2/cubic yard.
 
A perched beach structure would exacerbate rather than mitigate erosion due to an increase in alongshore current speed.
 
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UPPER NEWPORT BAY ESTUARINE ENHANCEMENT
 

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Client:  U.S. Army Corps of Engineers, Los Angeles District
 
Upper Newport Bay, one of the largest remaining wetlands in Southern California, provides habitat for a number of threatened and endangered plant and bird species.  During the past forty years, concern has grown over the long-term health of the estuarine environment.  Of particular importance is the impact of increased sedimentation from the 118 square mile watershed of San Diego Creek.  Coastal Frontiers was engaged by the U.S. Army Corps of Engineers to assist with the preparation of both Reconnaissance and Feasibility studies for environmental enhancement.
 
Study Tasks and Findings
 
Predict the changes that would occur over the next 50 years if no mitigative measures were taken - a course of action found to produce unacceptable sedimentation within the Upper Bay
 
Evaluate the costs and benefits of the following measures: channel dredging, sediment basin expansion, dike segmentation, mudflat creation, and relocation of a man-made island that provides habitat for the Least Tern
 
Develop six alternative plans to mitigate sediment accumulation while enhancing the estuarine environment using various combinations of the measures listed above
 
Based on the success of the Reconnaissance Study, Coastal Frontiers was asked to provide detailed technical analyses in support of the "Upper Newport Bay Ecosystem Feasibility Study" that followed.  The resulting plan of improvement has been implemented successfully over the past decade.


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CALIFORNIA BEACH RESTORATION STUDY
 

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Client:  California Department of Boating and Waterways
 
The loss of public beaches over the past century due to intense coastal and inland development as well as natural causes prompted the State of California to undertake the California Public Beach Restoration Program.  Coastal Frontiers served as a principal investigator and co-author of a supporting study that addressed the following topics:
 
Study Topics
 
Activities sponsored by the California Public Beach Restoration Program
 
Future needs for beach restoration, based on the prospective benefits associated with recreation, tourism, coastal access, public health and safety, habitat preservation, and property protection
 
Sand nourishment approaches applicable to California beaches, including sources, placement techniques, and maintenance requirements
 
The effectiveness of the present beach restoration program
 
Means of increasing the supply of sediment to the coast
 
The effectiveness of the California Public Beach Restoration Program was evaluated based on the outcome of prior and on-going nourishment projects.  Both deterministic and opportunistic projects were assessed, including a long-standing program of deterministic regional nourishment in Orange County and a series of opportunistic nourishment events in Santa Monica Bay.

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HYDRAULIC DESIGN OF THE SANTA ANA RIVER AND TALBERT CHANNEL OUTLETS
 

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Clients:  Simons, Li and Associates, Inc.; County of Orange; and U.S. Army Corps of Engineers
 
To mitigate the largest flood threat west of the Mississippi River, the U.S. Army Corps of Engineers undertook a major redesign of the Santa Ana River Outlet between Newport and Huntington Beaches in Orange County, California.  The challenges posed by this project included relocating the mouth of the Talbert Channel (a flood control channel in Huntington Beach), creating a new 92-acre tidal marsh off the Santa Ana River, enhancing an existing tidal marsh off the Talbert Channel, and providing nesting habitat for the endangered Least Tern while minimizing the loss of usable beach area and the impact on beachgoers.

Coastal Frontiers provided conceptual and preliminary coastal engineering design support for the upgraded Santa Ana River Outlet, and conceptual through final design support for the new Talbert Channel Outlet. 

Specific contributions were as follows:
 
Project Contributions
 
Analysis of coastal sediment transport and historical shoreline changes since construction of the original Santa Ana River Jetties in 1934
 
Analysis of the tidal exchange available to support wetland restoration
 
Design of quarrystone jetties for the Talbert Channel Outlet to provide reliable tidal exchange while maintaining the existing littoral transport regime
 
Three-dimensional model testing of wave propagation up the Talbert Channel during storm events
 
Presentation of project features and mitigative strategies at meetings with the regulatory agencies and general public
 
The Talbert Channel Project was selected as the outstanding Civil Engineering achievement in ASCE District 111 for 1994.


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REMOVAL OF PRATTE'S REEF - A MAN-MADE SURF ENHANCEMENT STRUCTURE
 

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Client:  Surfrider Foundation
 
In September 2000, the Surfrider Foundation installed an experimental surfing reef off Dockweiler State Beach in El Segundo, California. The structure, known as Pratte’s Reef, was constructed of sand-filled geotextile bags placed in a V-shaped configuration. The project objective was to mitigate the impacts on recreational surfing caused by the construction of a shore-perpendicular groin.

When Coastal Frontiers personnel inspected the reef in 2008, significant deterioration of the geotextile bags was noted, raising the possibility of fabric discharge into the marine environment. This finding, coupled with the reef's failure to produce a sustained enhancement in surf quality, prompted the Surfrider Foundation to initiate the first phase of a reef removal program in fall 2008. The second and final phase was conducted in 2010. 

Based on extensive past experience with the decomissioning of geotextile armor systems in the Arctic Ocean, Coastal Frontiers was engaged to perform the following tasks for the first-ever removal of a man-made surfing reef:
 
Reef Removal Tasks
 
Develop strategies for both vessel-based and land-based removal of 14-ton sand bags
 
Obtain all necessary permits from Federal, state, and local regulatory agencies
 
Map the reef outline prior to the initiation of removal activities
 
Provide on-site guidance for the professional dive crew, shore crew, and support vessel
 
Compile a list of lessons learned applicable to the removal of man-made surf enhancement structures
 
Key Findings
 
The efficiency of the removal effort is extremely sensitive to the prevailing wave and water level conditions
 
The cost of removing a geotextile-based nearshore structure can equal or exceed the cost of installation
 


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REGIONAL BEACH MONITORING PROGRAM - SAN DIEGO COUNTY
 

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Client:  San Diego Association of Governments (SANDAG)
 
The County of San Diego derives significant economic, recreational, and aesthetic benefits from its beaches.  To better understand the relevant coastal sediment processes and optimize the design of periodic regional beach nourishment programs, SANDAG engaged Coastal Frontiers to develop and implement a cost-effective and sustainable beach monitoring program in 1996.  Coastal Frontiers personnel have conducted semi-annual surveys and provided annual assessments of beach conditions since that time.

While the general objective of the program is to document changes in the condition of the shorezone while evaluating the impacts of natural events and human intervention, the focus in recent years has been the fate of nearly 2.1 million cubic yards of sand nourishment placed on the beaches in 2001 as part of the Regional Beach Sand Project (RBSP).  The lessons learned from this project have facilitated the planning, design and funding of a second beach nourishment effort (RBSP II) proposed for 2012.

The evolving nature of the monitoring program reflects an on-going collaboration between SANDAG and Coastal Frontiers to sharpen the focus of the effort while addressing the changing needs of SANDAG's constituents.  The current program consists of a beach component and a lagoon entrance component, with specific tasks listed below.
 
Study Tasks
 
Semi-annual beach profile surveys at up to 61 shore-perpendicular transects located between Oceanside and the U.S.-Mexico border
 
Annual oblique aerial photographs of beaches and lagoon entrances
 
Annual assessments of beach condition based on an analysis of changes in shoreline position and shorezone volume
 
Annual assessments of lagoon entrance condition based on closure records and maintenance activities (dredging and mechanical openings)
 


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BEACH PROFILE SURVEYS
 

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Clients:  U.S.  Army Corps of Engineers, Los Angeles District; Counties of Los Angeles, Orange, San Diego, Santa Barbara, and Ventura; Cities of Carlsbad, Encinitas, Long Beach, Newport Beach, San Clemente, and Solana Beach; Regional Authorities: BEACON, SANDAG; North Slope Borough; Southern California Edison; Members of the Petroleum Industry
 
Since 1986, Coastal Frontiers personnel have performed beach profile surveys to quantify changes in shoreline position and beach volume.  Much of the work has taken place in Southern California between Santa Barbara and the U.S. - Mexico border where the profiling effort has been repeated on a semi-annual basis to document seasonal changes at the end of the winter and summer wave periods.  Surveys also have been undertaken in remote locations that include Alaska and Siberia.

To accurately portray the condition of the beach, continuous data must be obtained from the backshore to the depth of profile closure.  Particular challenges arise in the surf zone where both vessels and swimmers must confront breaking waves and acoustic echo sounders are rendered useless by aeration in the water column.  Our survey methods typically include enhanced wading techniques and surf-tolerant inflatable vessels to insure data overlap in this critical region.
 
Typical Survey Objectives
 
Quantify changes in shoreline position and shorezone volume
 
Establish the depth of profile closure
 
Establish baseline conditions prior to initiating beach nourishment or structural stabilization projects
 
Monitor the effectiveness of beach nourishment projects and the impacts of coastal structures
 
Document the impacts of severe storms
 
Assess sedimentation at nearshore habitats
 
Define the landward limit of dredge operations
 
During the past two decades, Coastal Frontiers has performed more beach and nearshore monitoring programs in Southern California than all other non-governmental organizations combined.


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NUMERICAL MODEL OF SHORELINE EVOLUTION - SAN DIEGO COUNTY, CA
 

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Client:  U.S. Army Corps of Engineers, Los Angeles District
 
Since Oceanside Harbor was constructed in the 1940s, the downdrift beaches have experienced chronic erosion.  To quantify the impacts of the harbor structures and evaluate the effectiveness of candidate mitigation strategies, the U.S. Army Corps of Engineers' Los Angeles District engaged Coastal Frontiers to develop and implement a numerical simulation of long-term coastal change.

The model domain encompasses a 14-mile stretch of the coast in north San Diego County between the Santa Margarita River outlet and Agua Hedionda Lagoon.  In the first phase of the project, a Monte Carlo simulation of wave and water level conditions was used to hindcast shoreline evolution with and without the harbor present during the 64-year period from 1934 to 1998.  In the second phase, the model was used to forecast future shoreline evolution under scenarios that included no mitigative action, periodic beach nourishment, groin construction, nearshore reef construction, and combinations of nourishment and structural stabilization.
 
Key Model Attributes
 
Calibrated and verified using measured beach change during the 64-year hindcast period from 1934 to 1998
 
Flexible input parameters that include time-varying rates of beach nourishment, phased installation of sediment control structures, and varying rates of sea level rise
 
Comprehensive suite of output parameters that include shoreline change, wave overtopping, revetment damage, bore propagation over the backshore, and forces on backshore structures
 


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LARGE-SCALE TWO-DIMENSIONAL HYDRAULIC MODELS
 

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Clients:  Various Members of the Petroleum Industry
 
Since 1981, Coastal Frontiers personnel have conducted twelve two-dimensional hydraulic model studies in the large wave flume at Oregon State University to verify and refine the design of coastal protection systems.  The tests have encompassed armor types ranging from conventional quarrystone to innovative systems involving linked concrete mats, sand- and gravel-filled geotextile containers, and grout-filled geotextile containers.
 
Wave Flume at O.H. Hinsdale Wave Research Laboratory
 
360 ft long x 12 ft wide x 15 ft deep
 
Irregular and monochromatic waves with maximum heights in excess of 4 ft
 
Model scale ratios vary as large as 1:3
 
Accurate representations of armor stability, wave runup, and wave overtopping
 
Parameters Investigated
 
Armor stability
 
Slope deformation
 
Wave run-up elevations
 
Wave overtopping volumes
 
Effects of following wind
 


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THREE-DIMENSIONAL HYDRAULIC MODELS
 

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Clients:  Various Members of the Petroleum Industry, City of Long Beach, County of Orange
 
Coastal Frontiers personnel have conducted large-scale, three-dimensional physical model studies to investigate wave propagation, armor stability, sediment transport, and the effects of coastal structures.  Specific items of interest included refraction-diffraction effects, variations in wave characteristics around coastal structures, and sediment transport in the nearshore zone.

A representative example is a moveable bed model used to predict the effectiveness of beach nourishment coupled with a perched-beach at a Southern California location.  Salient findings included an acceleration of alongshore currents in the nearshore region accompanied by scour adjacent to the submerged rock structures used to create the perched beach.  The modeling effort, which was undertaken at the O.H. Hinsdale Wave Research Laboratory, is summarized below.
 
Wave Properties
 
Irregular and monochromatic wave generation
 
Variable wave direction
 
Parameters Investigated
 
Wave refraction and defraction
 
Sediment transport and beach change
 
Nearshore profile evolution
 
Wave attenuation over submerged structures
 
Seabed scour adjacent to structures
 
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