This report was prepared in 1996/97 as background information for the assessment of bypassing systems for the Tweed River Entrance Sand Bypassing Project. The information contained within this report has been obtained from a number of sources. The authors wish to thank all those who have provided assistance. In particular, the advice and feedback from project personnel within the Queensland Environmental Protection Agency, NSW Department of Land and Water Conservation, and Brown and Root as well as Queensland Transport, was greatly appreciated.

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World-wide Sand Bypassing Systems: Data Report

Los Angeles (LA) County's coastal areas are highly valued for their natural benefits and their economic contributions to the region. While LA County already has a high level of exposure to flooding (e.g. people, ports, and harbors), climate change and sea level rise will increase flood risk; anticipating this risk requires adaptation planning to mitigate social, economic, and physical damage. This study provides an overview of the potential effects of sea level rise on coastal LA County and describes adaptation pathways and estimates associated costs in order to cope with sea level rise. An adaptation pathway in this study is defined as the collection of measures (e.g., beach nourishment, dune restoration, flood-proofing buildings, and levees) required to lower flood risk. The aim of using different adaptation pathways is to enable a transition from one methodology to another over time. These pathways address uncertainty in future projections, allowing for flexibility among policies and potentially spreading the costs over time. Maintaining beaches, dunes, and their natural dynamics is the foundation of each of the three adaptation pathways, which address the importance of beaches for recreation, environmental value, and flood protection. In some scenarios, owing to high projections of sea level rise, additional technical engineering options such as levees and sluices may be needed to reduce flood risk. The research suggests three adaptation pathways, anticipating a +1 ft (0.3 m) to +7 ft (+2 m) sea level rise by year 2100. Total adaptation costs vary between $4.3 and $6.4 bn, depending on measures included in the adaptation pathway.

Pathways to resilience: adapting to sea level rise in Los Angeles

The principal function of a rubble mound breakwater is to protect a coastal area from excessive wave action. The dissipation of wave energy through absorbtion rather than reflection distinguishes rubble mound breakwaters from other types of fixed breakwater. A principal design objective is to determine the size and layout of the components of the cross-section. Designing and constructing a stable structure with acceptable energy absorbing characteristics continues to rely heavily on past experience and physical modelling. This paper outlines key design and construction issues, with particular regard to armour stability.

Design and Construction of Rubble Mound Breakwaters

: Stone deterioration on breakwaters and jetties arises from a combination of interactions pertaining to the quality of stone available, operational and handling practices at the quarry, and environmental weathering conditions after placement on the project structure. Four different and distinct investigations were essential to fully comprehend the mechanisms that give rise to chronic premature deterioration of armor stone on breakwaters and jetties around the Great Lakes.

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Monitoring Stone Degradation on Coastal Structures in the Great Lakes - Summary Report

: Monitoring Completed Navigation Projects (MCNP) Program evaluates the structural and functional performance of existing navigation structures. Under Periodic Inspections, aerial photography, ground-truth surveys, walking inspections, photogrammetry, and lidar elevation data are used to periodically assess the structural conditions of selected structures. A database of these structures is being compiled for asset management and other purposes. Cleveland Harbor East Breakwater, OH, has sustained extensive damage since its construction in 1915. The Breakwater has had an extensive repair history, including a major rehabilitation in 1979 80 involving the placement of 2-ton dolosse on the lakeward slope and crest of the easterly 4,400 feet (ft). Some failed and were replaced with 4-ton dolosse. Other repairs took place in 1986, 1989, 1991, and 2001 on the nondolos sections. Burns Harbor North Breakwater, IN, is a 4,640 ft rubble-mound structure constructed in 1969. The Breakwater has required extensive maintenance including the addition of 290 kilotons of stone through 1989. A submerged reef was constructed between 1995 and 1998, 75 ft lakeward of the Breakwater, to reduce wave energy reaching the structure.

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Periodic Inspections of Cleveland Harbor East Breakwater, Ohio, and Burns Harbor North Breakwater, Indiana

: An experimental model investigation was conducted using a two-dimensional stability model at an undisturbed linear scale of 1:28.5 (model to prototype). The purposes of the stability tests were as follows: (1) Evaluate the stability of the proposed 4-ton dolos trunk section (Plan 1) when exposed to design wave and still-water level (swl) conditions; (2) Determine the degree of breakwater damage that could occur in Plan 1 for a storm condition that exceeds the design condition; (3) Determine the maximum nonbreaking wave heights for which the existing 2-ton dolos design (Plan 2) and the proposed 4-ton dolos and 9- to 20-ton armor stone designs (Plan 3) could be considered to be adequately designed. Test results indicated that Plan 1 was only marginally acceptable and and would most likely require significant amounts of maintenance if exposed to design level wave conditions (7.0- to 9.0-sec, 13.4-ft nonbreaking waves at an swl of +4.9 ft low water datum (lwd)). Keywords; Armor stone, Dolosse.

Wave stability tests of dolos and stone rehabilitation designs for the East Breakwater, Cleveland Harbor, Ohio :

: Two-dimensional (2-D) and three dimensional (3-D) hydraulic model investigations were conducted at an undistorted linear scale of 1:25 (model to prototype) to acquire data on transmitted wave heights, mooring line forces, intermodule connector forces, bottom impact velocities, and barge angularities as a function of wave climate. These data were needed as input to optimize the design of the sloping float breakwater (SFB) concept whose function would be to protect floating dredges being used for sand bypassing at Oregon Inlet, N.C. The 2-D test indicated that for the 89.6- and 118.4-ft SFB's (a) the transmission response of both structures is strongly dependent on wave period; (b) increasing the water depth significantly decreases the wave-attenuating capabilities of both structures; (c) for most wave conditions, mooring forces are similar for both SFB lengths and tend to increase with increasing depth; and (d) peak flow velocities under the structure are generally higher for the longer SFB. The 3-D tests revealed that the existing barge connector concept would be subjected to extremely high forces during impact on a rigid bottom. A softer seafloor condition greatly reduced the connector forces, but since a soft bottom condition could not be guaranteed at all prototype sites, it was determined that the design of the existing connector system for highly rigid bottom-impact forces was not economically feasible. A connector system design that is isolated from these highly rigid bottom-impact forces is feasible, but needs further indepth study. (Author)

Sloping Float Breakwater Study Oregon Inlet, North Carolina, Coastal Model Investigation.

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King Harbor, Redondo Beach, California, breakwater stability study : hydraulic model investigation / by Ernest R. Smith, Willie G. Dubose, Robert D. Carver ; prepared for US Army Engineer District, Los Angeles.

King Harbor, Redondo Beach, California, breakwater stability study :

: A hydraulic model investigation of proposed breakwater modifications to King Harbor, Redondo Beach, California, was conducted at a geometrically undistorted scale of 1:35, model to prototype. Five breakwater cross sections were each subjected to 15 design wave and water-level conditions. Plans 1 through 3 consisted of variations of armor unit size on the rehabilitation sections. A transition layer of small stones was included in Plans 4 and 5 to reduce wave transmission. Data collected were displaced stones, qualitative overtopping observations, and wave transmission. Plan 5 gave the best combination of stability and reduction of wave transmission. Keywords: Breakwaters; Hydraulic models; Overtopping; Stability; Wave transmission.

Willie G. Dubose

Papers

Wave stability tests of dolos and stone rehabilitation designs for the East Breakwater, Cleveland Harbor, Ohio :

Sloping Float Breakwater Study Oregon Inlet, North Carolina, Coastal Model Investigation.

King Harbor, Redondo Beach, California, breakwater stability study : hydraulic model investigation / by Ernest R. Smith, Willie G. Dubose, Robert D. Carver ; prepared for US Army Engineer District, Los Angeles.

King Harbor, Redondo Beach, California, breakwater stability study :

King Harbor, Redondo Beach, California, Breakwater Stability Study: Hydraulic Model Investigation