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Benedet, L.; Finkl, C.W., and Dobrochinski, J.P.H., 2013. Optimization of nearshore dredge pit design to reduce impacts on adjacent beaches. The magnitude of the effects of nearshore dredge pits on adjacent beaches depends on a range of parameters, including seabed geomorphology, local wave climate, sediment supply, and pit design characteristics (e.g. distance offshore, depth of cut, cross-shore and alongshore extents, shape of pit). Delft3D, a morphological model developed by Deltares, was used to investigate relationships between dredge pit design parameters and impacts on adjacent beaches. The purpose of this study was to identify design parameters that affected the magnitude of dredge pit effects on adjacent beaches. An ancillary purpose was to develop a scientific basis for dredge pit design recommendations for beach restoration and other sediment needs of coastal infrastructure projects. Dredge pit design sensitivity tests were conducted using Delft3D. A schematic model was constructed usi...

Sandy bay beach in static equilibrium is the only physiographic feature that could remain stable without sediment supply in a persistent swell environment anywhere around the world. With a continuing trend of erosion to sandy beaches worldwide, a conservative and practical hypothesis is not to consider the mobile dynamic wave parameters but to safeguard against a sandy beach under vanishing supply in the future. To achieve this, an empirical bay shape equation is strongly recommended as one of the best coastal management options. Combining with MEPBAY, software derived for implementing the static bay beach concept on a display unit, this empirical bay shape equation is readily applicable to verify the stability of numerous headland bay beaches in natural and man-made condition. It is also adequate for coastal managers to apply this empirical equation as a valuable tool to aid in the creation of headland bay beaches for shore protection, recreation, and coastal management before embarking on sophi...

Beach erosion, a problem along most sandy shores, can be caused by man-induced interventions to the coast or natural processes. Remediation of beach erosion (i.e., beach restoration) along eroding developed beachfronts is commonly practiced in the United States by periodic beach renourishment with or without coastal structures. Rates of erosion within beach fills generally vary greatly, and areas that erode faster than the nourishment average are commonly termed erosional hot spots (EHSs). Delray Beach, located on the southeast coast of Florida, was renourished for the fourth time on December of 1992 with about 914,000 m3 of sand dredged from offshore and placed along 2.7 km of beach. About 448,000 m3 of the fill had eroded away by 2001, about eight and a half years after initial construction. Two beach segments with erosion rates higher than the nourishment average were identified based on analysis of annual beach profile data. About 40% of the eroded volume accrued from one of these beach segme...

Beach nourishment requires large volumes of sand from offshore and new sources are constantly sought for development. The sediment-starved continental shelf off the central-west coast of Florida has traditionally supplied beach-quality sediments from ebb-tidal shoals and nearshore sand sheets, but as these supplies dwindle, sand searches increasingly look farther offshore for resources. Widely spaced sediment ridges, interspersed by karstified limestone seafloor (hard grounds), offer potential as sand resources that can be exploited by dredging to renourish eroded beaches for shore protection. The sand ridges, late Holocene in age, are generally shoreface detached, sediment starved, and clustered in “ridge fields.” Six sediment ridge fields identified along 285 km of coast (Anclote, Sand Key, Sarasota, Manasota, Captiva, and Collier) contain about 1.4 billion cubic meters of sediments that are potentially available for dredging. Evaluation of these sediment sources, within the purview of the USMi...

Coastal land loss in the Mississippi River delta region, related to degradation of wetlands and erosion of barrier islands, contributes to loss of valuable habitat, endangerment of infrastructure and socioeconomic systems, and coastal flooding hazards. Restoration of these ecosystems is thus a primary activity that requires large volumes of sand to rebuild beach–dune systems and restore wetland habitats. Sand sources have traditionally been sought offshore in the marine environment, but there are problems associated with setbacks from oil and gas infrastructure, presence of muddy overburden, and limited reserves of beach-quality sediments. Fluvial sand sources in channel and point-bar deposits become an attractive alternative for barrier island restoration because of large volumes of relict deposits and because active sand waves are renewable. Results of preliminary geophysical and geotechnical investigations in the lower Mississippi River (south of New Orleans) along a 32-km stretch of the river...

Airborne laser bathymetry (ALB) is a new laser bathymetric survey tool that has applicability in clear coastal (Case II) waters to depths of −70 m. The new sounding technique features rapid acquisition of large, high-quality data sets via variable swath widths that are independent of water depth. This advanced ALB system was deployed along the continental shelf of southeast Florida (Palm Beach, Broward, and Miami-Dade Counties), providing a contiguous data set for 160 km of coast from onshore to 6 km offshore. Image enhancement of the ALB digital data facilitates recognition of numerous seafloor features and bathymetric patterns. Bathymetric analysis of the 600-km2 survey area on the continental shelf shows inherited lithologic features that are partly covered by surficial sediments. Primary parabathic (shore-parallel) provinces include: (1) nearshore rocky zones dominated by the Anastasia Formation, (2) coral-algal reef systems (Florida Reef Tract [FRT]), and (3) marine platforms (terraces). Sed...

Airborne laser bathymetric (ALB) systems rapidly acquire large, high-quality datasets via variable swath widths that are independent of water depth. Laser bathymetric survey tools have applicability in clear coastal (Case II) waters down to −70 meters depth. Deployed along the southeast Florida (Palm Beach, Broward, and Miami-Dade Counties) coast, an advanced ALB system provided a continuous dataset for 160 kilometers of coast from onshore to 6 kilometers offshore. Digital terrain models developed from this high-density bathymetric data permitted recognition of numerous seafloor features and bathymetric patterns from different image formats. Bathymetric analysis of the 600-km2 survey area on the narrow continental shelf shows inherited lithologic features that are partly covered by surficial sediments. Primary parabathic provinces include: (1) nearshore rocky zones dominated by the Anastasia Formation, (2) coral-algal reef systems (Florida Reef Tract [FRT]), and (3) marine terraces. Secondary sed...

Chronic erosion of beaches along the eastern Texas barrier island coast is increasingly mitigated by renourishment efforts that periodically place large volumes of sand onshore. Location of beach-quality sands on the inner continental shelf is challenged in an environment where terrestrial rivers deposit fluvial sediments in back bays and lagoons instead of offshore and by shelf areas that are dominated by muds. The search for beach-quality sands thus requires understanding of the coastal geological framework and morphodynamic processes that accompanied late Quaternary evolution in the northern Gulf of Mexico. The occurrence of surficial sand deposits as positive bathymetric features on the seafloor (ridges, shoals, banks) and presence of sands buried in paleovalley (drowned channels) infill sequences makes for complicated search procedures that must accurately differentiate a range of sedimentary settings by geophysical and geotechnical surveys. Compilation of vast amounts of data from historica...

Since 1973, Delray Beach, located on the southeast coast of Florida, U.S.A, has been periodically nourished. The morphological evolution of these nourishments has been influenced by design aspects (e.g., changes in shoreline orientation), extreme events (hurricanes, northeastern storms), and dredging of offshore borrow areas created to provide the nourishment sediments. This paper describes a thorough analysis of the physical processes influencing nourishment performance using the process-based model Delft3D. The analysis distinguishes three steps: (1) a wave analysis, (2) a hydrodynamic analysis, and (3) a morphological analysis. The wave analysis shows that the oldest, deeper, borrow pits (dredged in 1973 and 1978) have the largest effect on the nearshore wave climate, while the effects of the reefs can be considered negligible. Results from the hydrodynamic analysis indicate that differences in wave height cause variations in alongshore current velocities related to differences in wave setup a...