up of two parts: the airborne system and the ground-processing system. The airborne system uses a 400 Hz Nd: YAG infrared (1,064 nm) and a blue-green
(532 nm) laser transmitter with five receiver channels. The infrared frequency
measures the sea surface distance at nadir, while the blue-green frequency scans
below the sortie to measure marine depths and/or terrestrial elevations. SHOALS
can be mounted on a variety of aircraft, and is usually operated at an altitude of
200–400 m and speed of 117–140 knots. This configuration allows for data collection with a horizontal spot spacing of 4 m in a 100–300 m swath below the
aircraft.
In support of the RSMDP, several SHOALS surveys near Destin, Okaloosa
County, Florida were analyzed (Wozencraft and Irish 2000). In Destin, a navigable
depth of 4.3 m is authorized by the federal government for the tidal inlet of East
Pass, which connects Choctawhatchee Bay and the Gulf of Mexico. The first
surveys followed Hurricane Opal in 1995, which caused significant sediment infilling throughout the entire inlet system. The LiDAR survey detected this infilling,
and illustrated the need to dredge sand from the navigation channel, nourish
eroded adjacent beaches, and use it to repair breaches of Norriego Point. The
subsequent surveys occurred in 1996 and later, in 1997, to document the repair of
jetties along the mouth of the inlet. Additional rock was used to rebuild these
jetties, which were washed away by the storm surges of Hurricane Opal. This
survey also detected additional breaches of Norriego Point, despite previous efforts
to restore it using dredged material. By comparing the different depth surfaces
through time, the USACE was able to understand the morphological changes that
were taking place in this dynamic environment (Fig. 6.11). These depth surfaces
were also used to compute sediment volumes that were lost and gained during this
two year time period, allowing engineers to quantify the sediment budget of the
inlet and begin to explain the transport mechanisms (e.g., waves, tides, currents,
wind, etc.) driving this exchange of material.
The USACE has invested in data collection to support regional sediment
management by establishing the National Coastal Mapping Program (Wozencraft
and Lillycrop 2006). Using the NAVOCEANO CHARTS system, topographic
lidar, bathymetric lidar, aerial photography, and hyperspectral imagery are collected around the coast of the U.S. on a re-occuring schedule to provide the repeat,
high-resolution, high-accuracy data needed to perform these analyses for all USACE coastal projects (Reif et al. 2012).
6.2.7 Risk Assessment and Environmental Change
Climate change threatens coral reef ecosystems in several ways. Rising ocean
temperatures and increasing ocean acidification levels, in particular, may lead to
mass coral bleaching events and disease epidemics (Hoegh-Guldberg 2007). Climate change also threatens the livelihoods of communities that depend on coral
reef ecosystems, by altering the capacity to provide ecosystem goods and services,
162
S. J. Pittman et al.
(532 nm) laser transmitter with five receiver channels. The infrared frequency
measures the sea surface distance at nadir, while the blue-green frequency scans
below the sortie to measure marine depths and/or terrestrial elevations. SHOALS
can be mounted on a variety of aircraft, and is usually operated at an altitude of
200–400 m and speed of 117–140 knots. This configuration allows for data collection with a horizontal spot spacing of 4 m in a 100–300 m swath below the
aircraft.
In support of the RSMDP, several SHOALS surveys near Destin, Okaloosa
County, Florida were analyzed (Wozencraft and Irish 2000). In Destin, a navigable
depth of 4.3 m is authorized by the federal government for the tidal inlet of East
Pass, which connects Choctawhatchee Bay and the Gulf of Mexico. The first
surveys followed Hurricane Opal in 1995, which caused significant sediment infilling throughout the entire inlet system. The LiDAR survey detected this infilling,
and illustrated the need to dredge sand from the navigation channel, nourish
eroded adjacent beaches, and use it to repair breaches of Norriego Point. The
subsequent surveys occurred in 1996 and later, in 1997, to document the repair of
jetties along the mouth of the inlet. Additional rock was used to rebuild these
jetties, which were washed away by the storm surges of Hurricane Opal. This
survey also detected additional breaches of Norriego Point, despite previous efforts
to restore it using dredged material. By comparing the different depth surfaces
through time, the USACE was able to understand the morphological changes that
were taking place in this dynamic environment (Fig. 6.11). These depth surfaces
were also used to compute sediment volumes that were lost and gained during this
two year time period, allowing engineers to quantify the sediment budget of the
inlet and begin to explain the transport mechanisms (e.g., waves, tides, currents,
wind, etc.) driving this exchange of material.
The USACE has invested in data collection to support regional sediment
management by establishing the National Coastal Mapping Program (Wozencraft
and Lillycrop 2006). Using the NAVOCEANO CHARTS system, topographic
lidar, bathymetric lidar, aerial photography, and hyperspectral imagery are collected around the coast of the U.S. on a re-occuring schedule to provide the repeat,
high-resolution, high-accuracy data needed to perform these analyses for all USACE coastal projects (Reif et al. 2012).
6.2.7 Risk Assessment and Environmental Change
Climate change threatens coral reef ecosystems in several ways. Rising ocean
temperatures and increasing ocean acidification levels, in particular, may lead to
mass coral bleaching events and disease epidemics (Hoegh-Guldberg 2007). Climate change also threatens the livelihoods of communities that depend on coral
reef ecosystems, by altering the capacity to provide ecosystem goods and services,
162
S. J. Pittman et al.