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Abstract: Sea turtles nesting beaches are found near-globally, and the ability to characterize beaches by topographic and bathymetric features has remained largely out of reach. Twenty-one beaches and their offshore areas in southern Florida used by three sea turtle species (Caretta caretta, Chelonia mydas, and Dermochelys coriacea) were compared using topographic measures derived from LiDAR data. Variables such as slope, aspect, rugosity, and topographic and bathymetric position indices (TPI and BPI) were extracted from the LiDAR surface raster to characterize beaches used by sea turtles; stepwise multiple regression was used to determine which variables are most strongly associated with turtle nesting density. The three species exhibited tolerances for similar ranges of values in measured variables; beaches with values outside these tolerances were not used for nesting. Beach nesting density can be successfully modeled for all three species, but different topographic measures were important in each model. This work demonstrates the potential of high spatial resolution topographic datasets to successfully characterize coastal habitat for ecological applications. [Copyright &y& Elsevier]

Abstract: During the summer of 2005, Hurricane Dennis overwashed the eastern portion of St. George Island, part of the northwest barrier island chain located along the Florida Panhandle. In this paper, LiDAR-based morphological changes of the barrier island are analyzed, along with the short-term post-storm recovery of secondary dunes. Results show that overwash from the storm surge removed nearly the entire foredune complex, and the initial breaching probably occurred where the complex was either low or discontinuous; in these locations, beach widening was less. In contrast, approximately 10m of beach widening occurred where foredunes were higher and continuous, implying that more sediment was available for seaward transport during storm conditions. The secondary dunes recovered at an average linear rate of 3–4cm per month in the presence of vegetation, although monthly averages varied from −1.5 to 1.4m3/m and total volume changes varied from −17.9 to 16.4m3/m for the duration of the study. Furthermore, vegetation deterred dune migration, thus favoring dune growth and reducing erosion due to wind. In contrast, the absence of vegetation inhibited dune growth. Insignificant changes in elevation occurred in areas of storm debris or lag deposit. Finally, distributions of topographic gradients and curvature calculated numerically from pre- and post-storm LiDAR data are introduced as a potential tool in determining the relative post-storm recovery of the dune field. [Copyright &y& Elsevier]

The shape and amplitude of the bathymetric lidar waveforms (the recorded time history of the reflected lidar pulses) contain information about the attenuation of the water and the bottom reflectivity in the survey area. This study considers the factors that affect the amplitude of the bottom return and examines the use of the amplitude of the bottom return to distinguishing between different bottom types. The amplitude of the bottom return was corrected for pulse stretching and retro-reflectance due to the bottom slope based on a simple lidar radiative transfer model before the examination. Within-flightline and between-flightline variations of the bottom return were considered, both of which are related to the attenuation of water, surface wave condition, and bottom reflectivity. The major concern of within-flightline variation is the effect of surface waves on the reliability of bottom return. Between-flightline variation concerns the effect of change in viewing orientation on the bottom return from the same bottom type. A data set of Egmont Key, Florida, assuming homogeneous water clarity, was chosen to investigate the latter two effects on the bottom return signals. The result shows that the presence of surface waves is the most impeding factor that complicates the use of bottom return signal, as it can exaggerate the value (not prominent in our data) and variance of the amplitude of bottom return. A map of sand, continuous seagrass, and discontinuous seagrass ranging from the depth of 0. 8 to 4. 3 m was produced correctly from a single lidar flightline with limited in-situ information, in this case, a nadir viewing videotape concurrent with lidar survey mission. Finally, suggestions are proposed for ways to improve the production of a bottom map using the lidar waveform data. [Copyright &y& Elsevier]