Abstract
Breakwaters are a common shoreline protection structure, often trapping sediment as the incoming wave energy is reduced. Quantifying the dynamics and volume of these sediment sinks within a coastal system is an important step toward understanding the sediment budget for a particular coastal area. This study examines the volume of sediment deposited within the breakwater enclosed Point Judith Harbor of Refuge (Rhode Island, United States of America (USA)) in the late 19th century using seismic reflection profiles, bathymetric mapping, and isotopic analysis of core sediment. Geophysical profiles show a district seismic facies up to 4 m thick above the ravinement surface, particularly in the western and central portion of the harbor. Century-scale bathymetric changes revealed shoaling of a similar magnitude, and isotopic data support the deposition of this sediment package within the 20th century. The total volume of sediment within the harbor exceeds 5.0 × 106 m3, with an estimated sand volume of 3.6 × 106 m3. The results show that the harbor is a substantial sediment sink for the Rhode Island South Shore and provide the basis for future studies of the sediment budget for this shoreline.
Highlights
The use of armoring to protect coastal properties from storm impact, erosion, and sea-level rise has increased markedly since 1900 [1]
The aim of this paper is to describe a significant sediment sink for the Rhode Island South Shore (RISS) identified within the Point Judith Harbor of Refuge (HoR), a jetty/breakwater-enclosed harbor, using high-resolution seismic reflection profiling, sediment coring, and historic bathymetric surveys (Figure 1)
An integrated database of seismic reflection profiles, historic bathymetric data, and sediment cores demonstrates that the Point Judith Harbor of Refuge, a breakwater enclosed harbor along the Rhode Island South Shore, is a sediment sink with a total sediment volume of 5 × 106 m3 deposited above the ravinement surface within the harbor
Summary
The use of armoring to protect coastal properties from storm impact, erosion, and sea-level rise has increased markedly since 1900 [1]. Breakwaters, either detached or shore-connected, are common shoreline protection structures, designed to reduce wave energy, providing a safe harbor and some protection of the shorelines and vessels behind the breakwater [2]. Sediment deposition behind these structures is expected as the incoming wave energy is reduced [10], and the volume of newly deposited sediment provides an estimate of the rate and direction of sediment transport, which is key to assessing the sediment budget in coastal systems. Sediment budgets are typically based on the volume(s) of sediment that are the most well constrained within a system, and unknown or lesser known values can be approximated [12]
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