123-4 Monitoring and Assessing Coastal Change with Lidar: Historical Shoreline Movement and Beach and Dune Volumetric Trends along the Texas Gulf Coast

Session: Quaternary Research to Characterize Environmental and Geological Hazards

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Authors:

Abstract:

We determined shoreline movement rates and beach and foredune elevations and volumes for the Texas Gulf Coast using 2024 airborne lidar data and imagery. Sources of historical and recent shoreline positions along this dynamic coast include those depicted on aerial photographs from the 1930s to 2007, GPS surveys from the 1990s, and multiple airborne lidar surveys since 2000. Net rates of shoreline movement measured at 11,722 sites spaced at 50 m along the 590 km of Texas Gulf shoreline average 1.27 m/yr of retreat between the 1930s and 2024. Net shoreline retreat occurred along 81 percent of the Texas Gulf shoreline, resulting in an estimated net land loss of 6,979 ha since 1930. Shorter-term rates measured for the most recent period (2000 to 2024) are slightly lower, averaging 1.17 m/yr of net retreat. These rates, well below early- to mid-postglacial rates that range from 3 to 55 m/yr estimated from bathymetric shoreline proxies and past sea-level positions, are similar to mid- to late Holocene retreat rates of 0.1 to 1.7 m/yr. A relationship between postglacial relative sea-level rise rates and retreat rates calculated from the bathymetric shoreline proxy suggests that each millimeter per year of sea-level rise translates to 0.8 to 1.8 m/yr of shoreline retreat. This relationship provides an empirical approach to estimating future shoreline retreat rates under sea-level rise scenarios that may be similar to those observed during postglacial sea-level rise. Lidar-derived elevations and sediment volumes in the beach and foredune corridor generally correlate well with shoreline movement trends. Rapidly retreating shoreline segments have lower peak beach and foredune elevations than do segments where shorelines are more stable or advancing. Peak beach and foredune elevations are below 5 m elevation along nearly 52 percent of the Texas Gulf shoreline and are below 3 m elevation along about 18 percent of the shoreline. Beach and foredune sediment volume above 1 m elevation is estimated to be nearly 142,000,000 m³ along the Texas Gulf shoreline. Peak elevations and volumes above various threshold elevations can be used to identify shoreline segments where little sediment is available to offset sediment lost by erosion and segments vulnerable to breaching and washover during storm surge associated with tropical cyclone passage.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10015

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