Beaches in Space and Time by Dr. Richard A. Davis Jr

Author:Dr. Richard A. Davis Jr.
Language: eng
Format: epub
Publisher: Pineapple Press
Published: 2015-09-10T16:00:00+00:00

Figure 4.19

Heavy equipment moving borrow material into its proper place on the beach construction site

An even less costly and more simple nourishment approach is to remove the borrow material and transport it to a desired offshore site, commonly by hopper barge, then simply dump it at the desired depth and distance from shore. This would generally be only a few meters deep, because it is necessary for wave action to work on the sediment and carry it to the shoreline. Such a project was conducted at the southern portion of Padre Island, Texas, USA, with the sediment being placed at a depth of four meters. The borrow site was a ship channel a few kilometers away. The sediment was sucked into a hopper dredge, transported to the desired site, and dropped by opening the bottom of the dredge.

Nourishment Examples Beach nourishment projects are now being conducted throughout the world. The Atlantic Coast of the United States along with the entire Florida Peninsula has probably experienced the highest concentration of nourishment projects. Some of these have performed well, but others have not. Most of the poor performance of nourishment projects is due to the grain size of the borrow material and the wave energy, especially severe storms. Other parts of the world where nourishment has been used include Italy, Spain, the Netherlands, Denmark, China, Australia, and elsewhere. A few examples will provide some idea of how this all works.

Redington Beach, Florida, USA, provides a good picture of the before and after (figure 4.20) situation as well as the methodology of construction. This beach on the long, wave-dominated Sand Key barrier island on the west-central Florida Gulf Coast was eroding for several years, had a long vertical concrete seawall, and was in need of a major beach nourishment project. The borrow material was excavated by suction dredge from an ebb-tidal delta at Johns Pass, a nearby tidal inlet. It was pumped to the site and sculpted by machines as per the design plans. This was one of the first large nourishment projects on the Gulf Coast of the Florida Peninsula and was completed in 1988 (figure 4.20). It performed well and was followed by adjacent nourishment projects at each end of the initial one. Redington Beach has been subsequently renourished as was predicted.

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