Landslide Susceptibility and Ground Displacement Assessment of Austin City and Surroundings

The city of Austin and surrounding area is experiencing tremendous growth and expansion as a consequence of fast urban development and population growth. This has led to increased constructions and other anthropogenic alterations of the environment to accommodate the growing population and economy. These activities, coupled with the natural conditions and forcings, have made areas within the metropolis susceptible to the threats of landslides. The present study aims to identify zones in the study area that are susceptible to the threats of slow-moving creep/slow-slide landslide hazards and understand the factors and processes that control the occurrence of these events through an integrated study approach. This includes: (1) generating a landslide susceptibility (LS) map through a combination of the triggering factors including local geology and tectonic features, land use/cover, elevation/slope, and precipitation; (2) detect active deformation processes that could lead to landslide failure using Interferometric Synthetic Aperture Radar (InSAR) analysis techniques applied on Sentinel-1 SAR datasets (2015 2020) and validated through datasets from campaign GPS surveys and permanent stations; and (3) identify the factors and processes that directly or indirectly constrain the occurrence of the phenomenon through spatial analysis of relevant datasets. Our findings show: (1) the main concentration of vertical displacement (-1 to -6 mm/yr) is around the northern region of the study area; (2) zones with a moderate subsidence rate coincide with urbanized areas (up to -2 mm/yr) whereas pockets of high displacement rates (up to -6 mm/yr) are noted on NW parts; (3) most of the areas experiencing subsidence are underlain by the Comanche Series characterized by alternating beds of harder and softer limestones interbedded with beds of marly/clayey layers, and formations of marine marl, sandstone, and carbonaceous shale from the Gulf Series; (4) there is a high spatial correspondence between areas with high subsidence rates and high LS index; and (5) efforts are currently underway to analyze relevant datasets to determine factors and processes that control the occurrence of the hazard.