Methods for Investigating Sediment Flux under High-Energy Conditions on the Southeast Florida Continental Shelf using Laser Airborne Depth Sounding (LADS) in a Geographic Information System (GIS) Dataframe

Finkl, Charles W.; Vollmer, Heather M.

doi:10.2112/jcoastres-d-16a-00014.1

Cited by 6 publications

(4 citation statements)

References 13 publications

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“…7d). Our observations are consistent with previous bathymetric change analyses conducted along the northern FRT from 2001 to 2008 (approximately 3 years before Hurricane Ivan and 3 years after Hurricane Katrina) that showed movement of up to 1.8 Mm 3 of sediment between these time periods and transport of sediment from the inner shelf to offshore and beyond the shelf edge through gaps in the barrier reef and diabathic (cross-shore) channels during high-energy events or when the back reef overfills with sand (Finkl, 2004;Finkl and Vollmer, 2017). These observations are also consistent with results of Yates et al (2017) that show a multi-decadal trend along the FRT of reef sediment transport down the fore-reef-slope and export offshore.…”

Section: Discussionsupporting

confidence: 89%

“…Furthermore, wind conditions were relatively quiescent from the 2016 lidar acquisition date up to the passing of Hurricane Irma and after the storm, and historical aerial imagery of LKR from 2014 and 18 March 2017 (3 years and 6 months prior to Hurricane Irma, respectively, Fig. 9) show that patterns of major sedimentary features were mostly static (Finkl and Vollmer, 2017) in the few years prior to the storm. Our 2016 to 2017 elevation change results showed general movement of sediment and migration of major geomorphic features from ENE to WSW in shallow areas (ranging from approximately 2 to 5.5 m water depth in 2016) of the reef proper and back reef area, consistent with the direction of sustained, high magnitude winds during the passing of Hurricane Irma (Fig.…”

Section: Discussionmentioning

confidence: 99%

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Impact of Hurricane Irma on Coral Reef Sediment Redistribution at Looe Key Reef, Florida, USA

Yates,

Fehr,

Johnson

et al. 2023

Preprint

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Abstract. Understanding event-driven sediment transport in coral reef environments is essential to assessing impacts to reef species, habitats, restoration, and mitigation, yet there remains a global knowledge gap due to limited quantitative studies. Hurricane Irma made landfall in the Lower Florida Keys with sustained 209 km h-1 winds and greater than 8 m waves on 10 September 2017, directly impacting the Florida Reef Tract (FRT), and providing an opportunity to perform a unique comprehensive, quantitative assessment of its impact on coral reef structure and sediment redistribution. We used lidar and multibeam derived digital elevation models (DEMs) collected before and after the passing of Hurricane Irma over a 15.98 km2 area along the Lower FRT including Looe Key Reef to quantify changes in seafloor elevation, volume, and structure due to storm impacts. Elevation change was calculated at over 4-million point-locations across 10 habitat types within this study area for two time periods using data collected from 1) approximately one year before the passing of Irma and three to six months following the storm’s impact, and 2) from three to six months after, and up to 16.5 months after, the storm. Elevation-change data were then used to generate Triangulated Irregular Network (TIN) models in ArcMap to calculate changes in seafloor volume during each time-period. Our results indicate that Hurricane Irma was primarily a depositional event that increased mean seafloor elevation and volume at this study site by 0.34 m and up to 5.4 Mm3, respectively. Sediment was transported primarily west-southwest (WSW) and downslope modifying geomorphic seafloor features including the migration of sand waves and rubble fields, formation of scour marks in shallow seagrass habitat, and burial of seagrass and coral-dominated habitat. Approximately 16.5 months after Hurricane Irma (during a 13-month period between 2017 and 2019), net erosion was observed across all habitats with mean elevation-change of -0.15 m and net volume change up to -2.46 Mm3. Rates of elevation change during this post-storm period were one to two orders of magnitude greater than decadal and multi-decadal rates of change in the same location, and changes showed erosion of approximately 50 % of sediment deposited during the storm event as seafloor sediment distribution began to re-equilibrate to non-storm sea state conditions. Our results suggest higher resolution elevation-change data collected over seasonal and annual time periods could enhance characterization and understanding of short-term and long-term rates and processes of seafloor change and help guide post-storm recovery and restoration of benthic habitats in topographically complex coral reef systems.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Impact of Hurricane Irma on Coral Reef Sediment Redistribution at Looe Key Reef, Florida, USA

Yates,

Fehr,

Johnson

et al. 2023

Preprint

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“…Specifically, bottom- and surface-water signals are usually detected by airborne LiDAR bathymetry (ALB) systems (more commonly known as full-waveform bathymetric LiDAR systems) using the two bands (532 and 1064 nm) that can detect these signals, respectively [ 4 , 5 ]. Dual-frequency ALB systems such as coastal zone mapping and imaging LiDAR (CZMIL) [ 6 ], laser airborne depth sounder (LADS) [ 7 , 8 ], Hawkeye II, and Hawkeye III [ 9 ] are large and heavy and have strong energy-emission requirements. Hence, their applications are often limited, and single-beam ALB systems that are inexpensive, lightweight, flexible, and have high accuracy and multi-platform adaptability (e.g., unmanned aerial vehicle (UAV) platform) are more preferred in bathymetry and underwater mapping [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

An Assessment of Waveform Processing for a Single-Beam Bathymetric LiDAR System (SBLS-1)

Chen

Liu

Lin

et al. 2022

Sensors

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The single-beam bathymetric light detection and ranging (LiDAR) system 1 (SBLS-1), which is equipped with a 532-nm-band laser projector and two concentric-circle receivers for shallow- and deep-water echo signals, is a lightweight and convenient prototype instrument with low energy consumption. In this study, a novel LiDAR bathymetric method is utilized to achieve single-beam and dual-channel bathymetric characteristics, and an adaptive extraction method is proposed based on the cumulative standard deviation of the peak and trough, which is mainly used to extract the signal segment and eliminate system and random noise. To adapt the dual-channel bathymetric mechanism, an automatic channel-selection method was used at various water depths. A minimum half-wavelength Gaussian iterative decomposition is proposed to improve the detection accuracy of the surface- and bottom-water waveform components and ensure bathymetric accuracy and reliability. Based on a comparison between the experimental results and in situ data, it was found that the SBLS-1 obtained a bathymetric accuracy and RMSE of 0.27 m and 0.23 m at the Weifang and Qingdao test fields. This indicates that the SBLS-1 was bathymetrically capable of acquiring a reliable, high-efficiency waveform dataset. Hence, the novel LiDAR bathymetric method can effectively achieve high-accuracy near-shore bathymetry.

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“…The effects of water level variation on sediment mobility and transport have also been considered for Pacific fringing reefs; Storlazzi et al () found that sea level rise would reduce frictional wave dissipation over the reef crest and flat, resulting in stronger wave‐driven currents and enhanced sediment transport on the inner reef. On the Atlantic coast, comparisons of bathymetric surveys before and after two hurricanes (Ivan, 2004, and Katrina, 2005, in the Florida Reef Tract) indicate sediment is mobilized and transported during extreme storms (Finkl & Vollmer, ), although the hydrodynamic processes that drove this response were not quantified. The bulk of previous work on coral reef hydrodynamics, wave interaction, and sediment transport has focused on high‐relief reefs such as those found in the Pacific Ocean.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics and Sediment Mobility Processes Over a Degraded Senile Coral Reef

et al. 2018

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Coral reefs can influence hydrodynamics and morphodynamics by dissipating and refracting incident wave energy, modifying circulation patterns, and altering sediment transport pathways. In this study, the sediment and hydrodynamic response of a senile (dead) barrier reef (Crocker Reef, located in the upper portion of the Florida Reef Tract) to storms and quiescent conditions was evaluated using field observations and the Coupled Ocean-Atmosphere-Wave-Sediment Transport model. Waves, circulation, and resultant sediment mobility were modeled across different reef zones. Sediment mobility during quiescent periods and the passage of far-field storms are driven by nonbreaking waves and, to a lesser degree, regional circulation. Spatial variability in these processes produces the present-day distribution of sediment grain size at Crocker Reef, wherein finer-grain material along a shallow central ridge is frequently mobilized (43% to 62% of the time), winnowed away, and deposited along the lower-energy flanks and in the fore reef where sand mobility occurs less frequently (32% to 43% and 1% to 22% of the time, respectively). Analysis of wave conditions for the period of 2006-2014 supports that wave heights rarely exceed the threshold for breaking (0.1% and 0.3% at the reef crest and at the reef flat, respectively), predominantly during the passage of tropical storms. There is a shift to a wave-breaking regime during near-field storms, creating the potential for mobilization of larger material and enhanced reef degradation. Sediment mobility can be enhanced due to wave skewness or the generation of free infragravity waves during periods of depth-induced wave breaking.

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Methods for Investigating Sediment Flux under High-Energy Conditions on the Southeast Florida Continental Shelf using Laser Airborne Depth Sounding (LADS) in a Geographic Information System (GIS) Dataframe

Cited by 6 publications

References 13 publications

Impact of Hurricane Irma on Coral Reef Sediment Redistribution at Looe Key Reef, Florida, USA

Impact of Hurricane Irma on Coral Reef Sediment Redistribution at Looe Key Reef, Florida, USA

An Assessment of Waveform Processing for a Single-Beam Bathymetric LiDAR System (SBLS-1)

Hydrodynamics and Sediment Mobility Processes Over a Degraded Senile Coral Reef

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