2.2.2 Direct Deposit of Fill
Dunes are frequently constructed by directly depositing sediment and reshaping it
using earth-moving equipment. These landforms, often called dune-dikes, are
usually built to optimize a flood-protection function and often have a flat top or
planar sides of a consistent slope with little topographic diversity (Fig. 2.2).
Dune-dikes may retain their artificial form through time if no subsequent aeolian
accretion occurs or if they are rebuilt to the same template when they erode. They
may eventually evolve to resemble more hummocky natural dunes with greater
variability of microhabitats if they are not repeatedly rebuilt or revegetated.
The grain size characteristics, rates of change, and characteristic vegetation of
dunes built by mechanical placement differ from dunes created by aeolian deposition
(Baye 1990; van der Wal 1998; Matias et al. 2005). Bulldozed dunes may include
coarser shells and gravel, but they can have well-sorted sands that resemble dune
sediments if suitable borrow areas are used to build them. Bulldozed dunes can
provide habitat similar to natural dunes, if actions are taken to enhance this value
during and after construction. Patchiness of habitats can be increased by creating an
undulating foredune crest, resulting in local differences in drainage and wind speed
and converting the landward boundary from a line into a zone (Nordstrom 2008).
Subsequent deposition of wind-blown sand on a bulldozed dune can create surface
characteristics similar to a natural dune if no barriers to aeolian transport are created
seaward of it. This deposition can be accelerated by using beach fill materials
compatible with aeolian transport, employing sand-trapping fences on (but not in
front of) the nourished dune, and creating a gentle seaward slope in the initial fill
deposit (Matias et al. 2004, 2005).
Fig. 2.2 Dune at Carolina
Beach, NC, USA (1981),
created using artificial fill
reshaped by bulldozers into a
dune-dike
2 Foredune Restoration
21
Dunes are frequently constructed by directly depositing sediment and reshaping it
using earth-moving equipment. These landforms, often called dune-dikes, are
usually built to optimize a flood-protection function and often have a flat top or
planar sides of a consistent slope with little topographic diversity (Fig. 2.2).
Dune-dikes may retain their artificial form through time if no subsequent aeolian
accretion occurs or if they are rebuilt to the same template when they erode. They
may eventually evolve to resemble more hummocky natural dunes with greater
variability of microhabitats if they are not repeatedly rebuilt or revegetated.
The grain size characteristics, rates of change, and characteristic vegetation of
dunes built by mechanical placement differ from dunes created by aeolian deposition
(Baye 1990; van der Wal 1998; Matias et al. 2005). Bulldozed dunes may include
coarser shells and gravel, but they can have well-sorted sands that resemble dune
sediments if suitable borrow areas are used to build them. Bulldozed dunes can
provide habitat similar to natural dunes, if actions are taken to enhance this value
during and after construction. Patchiness of habitats can be increased by creating an
undulating foredune crest, resulting in local differences in drainage and wind speed
and converting the landward boundary from a line into a zone (Nordstrom 2008).
Subsequent deposition of wind-blown sand on a bulldozed dune can create surface
characteristics similar to a natural dune if no barriers to aeolian transport are created
seaward of it. This deposition can be accelerated by using beach fill materials
compatible with aeolian transport, employing sand-trapping fences on (but not in
front of) the nourished dune, and creating a gentle seaward slope in the initial fill
deposit (Matias et al. 2004, 2005).
Fig. 2.2 Dune at Carolina
Beach, NC, USA (1981),
created using artificial fill
reshaped by bulldozers into a
dune-dike
2 Foredune Restoration
21