11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 17: Emerging Techniques in Remote Sensing and Geospatial Analysis
17-17
Fore-and Back-Reef Environments Interpreted from Airborne Laser Bathymetry:
Northern Extension of the Florida Reef Tract Offshore SE Florida
Charles FINKL* 1 , Jeffrey ANDREWS 1 , William ROBERTSON 1 , Beth FORREST 1
1 Coastal Geology & Geomatics, Coastal Planning & Engineering, Boca Raton, FL
The northern extension of the Florida Reef Tract (FRT) off SE Florida terminates in
northern Palm Beach County at a southeast trending magnetic lineament known as the
Bahamas Fracture Zone (BFZ). South of this morphostructural boundary, the FRT
separates into a range of topologies that are based on interpretations of color-ramped
imageries derived from airborne laser bathymetry (Laser Airborne Depth Sounding,
LADS). LADS provided a contiguous data set in clear coastal waters to -70 m depth for
160 km of coast from onshore to about 6 km offshore. Enhancement of the LADS digital
data permitted recognition of bathymetric patterns in the 600-km2 shelf survey area.
Primary parabathic provinces include: (1) nearshore rocky zones dominated by
limestones, (2) coral-algal reef systems (spur and groove topography, forereef rubble
fields, back reef overwash deposits), (3) inter-reefal sediment troughs (partially infilled
paleo mote systems) between barrier reef tracts, and (4) deep water marine terraces (paleo
coral reefs) near the shelf break. Secondary sedimentary subprovinces include back reef
shoreface sands, bar and trough systems, and reef gap ramps. Tertiary topographic
features include drowned karst topography that was formed during glacio-eustatic
lowering of sea level and subaerial exposure of reefs and limestone bedrock surfaces.
Hierarchical organization of these bathymetric features is now possible due to the
increased accuracy and density of bathymetric data in LADS format. Application of
airborne laser bathymetric imagery for the first time permitted comprehensive
differentiation of the world’s third largest barrier reef environment along the southeast
coast of the Florida Peninsula, separating the northern extension of the FRT from
drowned beach ridge plains to the north and the Florida Keys to the south.
17-18
Integrated Multi-Sensor Remote Sensing Of The Terrace Structure Of The Shallow
Dry Tortugas Coral Reef Ecosystem
John BROCK* 1 , Monica PALASEANU-LOVEJOY 1 , Nayegandhi AMAR 1 , C. Wayne
WRIGHT 2
1 USGS, St. Petersburg, FL, 2 Wallops Flight Facility, NASA, Wallops Island, VA
Terraces have been recognized in many reef systems around the world and on last
interglacial reefs this geomorphology has been linked to changes in sea level regimes. In
parallel, many reef systems have an ecological zonation that correlates coarsely with
geomorphology. Benthic habitat mapping of coral reef ecosystems is typically
accomplished by the classification of multi-spectral images acquired from satellites or
aircraft, an approach that omits the use of reef morphology in defining habitat
boundaries. Aircraft lidar surveys can map fine scale reef structure, and enable the
recognition of terraces on shallow coral reef ecosystems that may control the distribution
of benthic communities.
The hypothesis that the shallow Dry Tortugas coral reef ecosystem is
geomorphologically organized into terraces that act to control ecological zonation was
evaluated. Following a NASA airborne lidar survey in August 2004 that resulted in a
one-meter scale topographic map, the Wilcox signed rank test was used to verify the
presence of terraces on Garden Key Bank, Pulaski Bank and Loggerhead Key Bank, the
major geomorphic units of the shallow Dry Tortugas. Next, the boat-mounted Along
Track Reef Imaging System (ATRIS) was used to collect voluminous observations of
benthic class and topographic complexity to investigate correlation between the
recognized terracing and the spatial structure of benthic habitats. A Jaccard dissimilarity
analysis of interpreted ATRIS benthic images collected on transects across all three major
banks of the Dry Tortugas revealed significant within and between bank differences in
terrace benthic community composition.
17-19
The View From Above -Are Reefs Fractal Because Of Neutral-Random Construction?
Samuel PURKIS* 1 , Kevin KOHLER 1 , Bernhard RIEGL 1
1 National Coral Reef Institute, Nova Southeastern University, Dania Beach, FL
Satellite remote sensing has shown numerous aspects of coral reef seascapes to be fractal. That
is they display characteristics of scale-invariance and complexity. This property is pervasive
and recognised in the geometries of both framework and lagoonal bedforms in reefal settings
across the Pacific. To date, the interpretation of this curious scaling has been hampered by a
lack of understanding as to why the morphometrics of reefs should be fractal. We investigate
this property using high-resolution terrain models of the shallow Puerto Rico insular shelf built
using bathymetric LiDAR soundings. We find that a computer-simulation model constructed
using simple random processes is adequate to describe the intricacies of actual coral reef terrain.
This model, based on fractional-Brownian motion (fBm), produces surfaces that are visually
and statistically indistinguishable from natural seabeds, at spatial scales of 0.001 - 25 km 2 . The
conformity between model and nature prompts us to question whether the processes used in the
simulation can provide insight into the construction of real-world reef platforms. Through this
comparison we are able to identify simple natural processes that mimic the construction of the
modelled terrains. We demonstrate that random settlement of coral colonies, followed by
focused development of topographic highs, is sufficient to explain the production of fBm-like
reef terrain. Importantly, this negates the requirement for secondary factors such as complex
lateral interactions between habitat types, and/or the overprinting of landscape-altering
processes such as sedimentation and erosion, to produce a fractal reef surface. By comparison,
for terrestrial systems, such secondary processes have been identified as a necessary precursor
for the creation of a fractal landscape. The findings of this study add weight to the hypothesis
that the fractal property of reef terrain is the product of many simple random processes
interacting at a variety of scales.
17-20
Coastal Zone Classification Using Data Fusion Between Lidar And Hyperspectral Data
Jennifer WOZENCRAFT* 1 , Christopher MACON 1 , Grady TUELL 2 , Joong Yong PARK 2
1 USACE - JALBTCX, Kiln, MS, 2 Optech International, Kiln, MS
Bathymetric lidar systems have been producing high resolution depth data since the late
90's.With developments in remote sensing technology and techniques the bathymetric depth
map is just one of many products produced by the Compact Hydrographic Airborne Rapid Total
Survey (CHARTS) system. CHARTS is owned by the Naval Oceanographic Office (NAVO)
and operated through the Joint Airborne Lidar Bathymetry Technical Center of Expertise
(JALBTCX) with the U.S. Army Corps of Engineers (USACE).
The CHARTS system is a combination of multiple sensors including the Optech SHOALS-
3000T20E ( 3 kHz bathymetric lidar, 20 kHz topographic lidar, and 1Hz RGB camera) and an
Itres CASI-1500 hyperspectral imager. The CASI-1500 is programmable to collect between 4
to 288 spectral bands ranging from 380 nm to 1050 nm. The sensors share the same rigid
platform allowing them to each use the same inertial navigation solution.
Since the integration of the CASI-1500 with the SHOALS-3000T20E, Optech International has
been developing the Rapid Environmental Assessment (REA) processor. The REA processor
fuses the lidar and hyperspectral image data at many levels to produce topographic land cover
and bathymetric seafloor classifications with higher accuracy than previously possible. At the
signal level, information extracted from the lidar waveform is used to invert the radiative
transfer model for seafloor reflectance in the hyperspectral imagery. At the classification level,
independent classifications based on lidar parameters like depth, bottom reflectance, and bottom
roughness and on the hyperspectral bottom reflectance are merged using the Dempster-Schafer
algorithm.
In January 2007, JALBTCX collected topographic, bathymetric, and hyperspectral data in and
around Hilo Bay, Hawaii. Using these datasets and the Optech REA processor, JALBTCX has
produced the first production level lidar and hyperspectral fusion derived seafloor
classifications.
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