IV. Retreating Shorelines
279
Along the New Jersey shore (Cape May Point, Belmar and Spring Lake Juntion,
Avalon) three installations currently check physical performance against
computer projected sand retention.
3.7
Assessments
Numerous studies have been conducted to measure the results obtained with
beach nourishment. Many are encouraging. They have been carried out a.o. by
the U.S. Army Corps of Engineers, also by HAECON N.V. (Ghent, Belgium). In
some cases new techniques have been tried out, for instance with multiple-layered
beach fill.
A beach fill composed of a base layer of hydraulically-placed, silty sand covered
with a coarser, land-hauled sand layer has stabilized 2.3 kilometers (1.4 mi) of
recreation shoreline in Corpus Christi Bay TX for 10 years. It is an example of
how to restore low-to-moderate wave energy beaches where suitable deposits are
either limited in extent, or expensive to exploit. The overall stability of the beach
fill design suggests the concept has merit and may serve as an alternative to
homogeneous beach fills when conditions warrant. The beach has experienced
erosion since the late 1800's. (James M. Kieslich and Dewey H. Brunt III, 1989,
Assessment of a Two-Layer Beach Fill at Corpus Christi Beach, TX : Coast.
Zone '89, 3975-3983)
The longer the nourishment distance, the smaller the loss of material.
Furthermore, structures placed near the ends of a beach nourishment project can
reduce materials losses. Submerged shore-parallel structures limit seaward
transport of sediment (a.k.a. "perched beach concept") particularly when fed
material is finer than the original beach sand.
Most successful schemes have been reported between headlands because removal
can take place only transverse to the beach (cf. chapter Ill.4). Loss to the offshore
depends on submarine slopes that must fill before an equilibrium status is
reached. Calculation of the beach profile will help to determine amount of fill
required. Silvester (op. cit.) has commented that sediment coarser than the
original will lead to a steeper than original slope, while the opposite occurs with
finer than original fill. However, as we mentioned earlier (3.1.) a steeper beach
slope may result in wave reflection, which accelerates removal of finer material
and exacerbates the existing erosion problem.
279
Along the New Jersey shore (Cape May Point, Belmar and Spring Lake Juntion,
Avalon) three installations currently check physical performance against
computer projected sand retention.
3.7
Assessments
Numerous studies have been conducted to measure the results obtained with
beach nourishment. Many are encouraging. They have been carried out a.o. by
the U.S. Army Corps of Engineers, also by HAECON N.V. (Ghent, Belgium). In
some cases new techniques have been tried out, for instance with multiple-layered
beach fill.
A beach fill composed of a base layer of hydraulically-placed, silty sand covered
with a coarser, land-hauled sand layer has stabilized 2.3 kilometers (1.4 mi) of
recreation shoreline in Corpus Christi Bay TX for 10 years. It is an example of
how to restore low-to-moderate wave energy beaches where suitable deposits are
either limited in extent, or expensive to exploit. The overall stability of the beach
fill design suggests the concept has merit and may serve as an alternative to
homogeneous beach fills when conditions warrant. The beach has experienced
erosion since the late 1800's. (James M. Kieslich and Dewey H. Brunt III, 1989,
Assessment of a Two-Layer Beach Fill at Corpus Christi Beach, TX : Coast.
Zone '89, 3975-3983)
The longer the nourishment distance, the smaller the loss of material.
Furthermore, structures placed near the ends of a beach nourishment project can
reduce materials losses. Submerged shore-parallel structures limit seaward
transport of sediment (a.k.a. "perched beach concept") particularly when fed
material is finer than the original beach sand.
Most successful schemes have been reported between headlands because removal
can take place only transverse to the beach (cf. chapter Ill.4). Loss to the offshore
depends on submarine slopes that must fill before an equilibrium status is
reached. Calculation of the beach profile will help to determine amount of fill
required. Silvester (op. cit.) has commented that sediment coarser than the
original will lead to a steeper than original slope, while the opposite occurs with
finer than original fill. However, as we mentioned earlier (3.1.) a steeper beach
slope may result in wave reflection, which accelerates removal of finer material
and exacerbates the existing erosion problem.