Shoreline and Sand Storage Dynamics from Annual Airborne LIDAR Surveys, Texas Gulf Coast

ABSTRACT Paine, J.G.; Caudle, T.L., and Andrews, J.R., 2017. Shoreline and sand storage dynamics from annual airborne LIDAR surveys, Texas Gulf Coast. Annual airborne LIDAR surveys were conducted along the Texas Gulf of Mexico shoreline between 2010 and 2012 to map shoreline position, determine shoreline movement and its historical context, and quantify beach and dune morphology by determining elevation threshold area (ETA) relationships for Holocene barrier islands, strandplains, and fluvial and deltaic headlands and marshes. Historical (1800s to 2007) movement is erosional for all major Texas shoreline segments, averaging 1.3 m/y of retreat. Shorelines retreated between 2007 and 2010 at a higher average rate of 2.8 m/y because of erosion and partial recovery from Hurricanes Ike (2008), Humberto (2007), and Dolly (2008). Despite the erosional context, airborne LIDAR surveys show that the shoreline advanced at 75% of 11,783 monitoring sites between 2010 and 2011 and moved an average of 6.5 m seaward during storm recovery. The recovery reversed between 2011 and 2012, when the shoreline retreated at 67% of 11,811 sites and moved an average of 3.1 m landward. Movement was similar to historical trends: NE and southern coast shorelines retreated, whereas central coast shorelines were relatively stable. Retreat between 2011 and 2012 did not fully offset advance between 2010 and 2011; the shoreline advanced at 59% of 11,811 sites and moved an average of 3.4 m seaward between 2010 and 2012, resulting in a net area gain of 203 ha. LIDAR-derived beach and dune areas exceeding threshold elevations of 2–9 m above mean sea level (at 1-m increments), divided by shoreline length over which the ETAs were determined, were used to produce average profiles. These data can be used to determine sediment storage volumes and temporal change, flood susceptibility, and erosion resilience. Storage patterns evident in ETA data mimic historical shoreline movement. Low elevation and sand storage occur where retreat is highest, whereas higher elevation and storage occur where retreat is lowest.

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