Deriving Morphological Changes in the Eastern Flank of the Brazos River Delta Using Terrestrial Laser Scanning and GPS

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2017-05

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Abstract

Terrestrial laser scanning (TLS) techniques have proven to be efficient to collect three-dimensional high-density and high-accuracy point clouds for coastal research and resource management. LiDAR-based bare-earth digital elevation models (DEMs) are widely used for quantification analysis of beach and dune morphological changes in time and space. This study aims to quantify the morphological changes in the vicinity of the Brazos River delta in Freeport, Texas during the period from summer of 2015 to winter of 2016 using the TLS and GPS integrated techniques. TLS collects a massive amount of surveying points. The processing and presentation of the large volumes of datasets is always a challenge for research when targeting large areas. This study developed a practical workflow for TLS data acquisition and massive data processing, and for the analysis of digital elevation models (DEMs) aimed to derive coastal morphological changes. Four repeated TLS datasets were collected in May and December of 2015, and May and December of 2016. Four high-resolution DEMs were generated following the workflow introduced in this study. The changes of shoreline, vegetation line, dune ridge, volume, and beach profiles were investigated by utilizing the high-resolution and highly accurate DEMs. The final analysis and visualization of results were completed using ArcGIS. Results from this study indicate that significant beach erosion happened since the summer of 2015 to the winter of 2016. The short-term rate-of-change and net movement are higher than those calculated in previous long-term studies in the Freeport beach region. On average, the shoreline retreated 15.6 m since May 2015 to December of 2016. The change of the dune ridge is minor. However, the changes of vegetation line and dune volume are significant. The short-term rapid topographic change in the Freeport beach and dune was caused mainly by several storm flood events that affected the Texas coast in May of 2015 and April of 2016. It is expected that this study will promote the applications of the GPS and TLS techniques in coastal erosion and other natural hazards studies in Texas and other natural hazard-prone areas.

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Keywords

Terrestrial laser scanning (TLS), GPS, Coastal morphology

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