Tiffany L. Caudle, Thomas A. Tremblay, Jeffrey G. Paine, John R. Andrews, Kutalmis Saylam, and Aaron Averett Bureau of Economic Geology Jackson School of Geosciences The University of Texas at Austin American Shore and Beach Preservation Association National Coastal Conference October 2013 Tracking Shoreline and Geomorphic- Unit Change on South Padre Island, Texas Using Chiroptera Mapping System

Project Acquire topographic and bathymetric lidar data and color infrared aerial imagery Tasks: –Map 2013 shoreline, vegetation line and dune crest –Update change rates of shoreline position –Map geomorphic units –Beach-dune system volume analysis –Sediment budget

BEG’s Chiroptera Airborne Lidar System Laser System PRR, Topo: 400kHz PRR, Bathy: 36kHz 40 degree swath λ = 1µm, 0.5 µm Camera DigiCAM 50 MP 8176 x 6132 px RGB, Color IR

Red laser Green laser 50 MP Camera (RGB), CIR) Cessna 206 Flight Direction BEG’s Chiroptera Airborne Lidar System

South Padre Island Survey Flown February 2013 (2 days) Beach, dune, and nearshore environments along 79 km of shoreline (to 1 km offshore) Topographic (200kHz) and bathymetric (36kHz)lidar data and hi-res Color I/R imagery 8-10 points per sq m

Topo data and CIR images 500-m swath landward of the shoreline Bathy data collected 1000 m seaward of shoreline −Intent to establish depth-penetration and water-clarity limits in Gulf of Mexico

Topographic Lidar Point Cloud Elevation Intensity

SHORELINE CHANGE

Lidar Shoreline Positions

Short-term Shoreline Change Rates Sites Max Erosion: m/yr Max Accretion: m/yr Average Rate: 1.75 m/yr 36% of sites eroding (483) 64% of sites accreting (865)

Decade-scale Shoreline Change Rates Sites Max Erosion: m/yr Max Accretion: 2.67 m/yr Average Rate: m/yr 76% of sites eroding (1024) 24% of sites accreting (322)

Long-term Shoreline Change Rates Sites Max Erosion: m/yr Max Accretion: 4.48 m/yr Average Rate: m/yr 84% of sites eroding (1134) 16% of sites accreting (216)

GEOMORPHIC UNIT MAPPING

Geoenvironments of South Padre Island

Geoenvironments Mapping Methods

Geoenvironments Washover Mapping

Summary Topographic and bathymetric lidar survey of SPI flown in early February 2013 Comparison of 2013 lidar derived shoreline position with positions extracted from data to determine short-term rates of shoreline change (ave m/yr accretion for SPI) Calculate decade-scale (-1.12 m/yr) and long-term (-2.15 m/yr) rates of shoreline change Lidar DEM beneficial for geoenvironments mapping Continue analysis of bathymetric lidar data to establish depth-penetration and water-clarity limits in Gulf of Mexico

PRELIMINARY BATHYMETRIC RESULTS

water surface bottom ground truth 0.8 m 2 m 2.2 m 1.4 m

water surface bottom ground truth 3.3 m2.77 m3.5 m

m m

Tiffany L. Caudle Bureau of Economic Geology John A. and Katherine Jackson School of Geosciences The University of Texas at Austin Thank you!