Synthesizing subsidence, sea-level rise, and storm surge scenarios for Houston-Galveston, Texas

Abstract:

In 2017, Hurricane Harvey flooding devastated Houston and Galveston, Texas, and highlighted shortcomings of flood resilience plans. Both anthropogenic and natural land subsidence is correlated with flooding observed during the storm (Miller & Shirzaei, 2019). Climate change threatens to further exacerbate coastal flooding hazards in eastern Texas. To advance understanding of future flooding and inundation risks and severity, surface deformation is combined with sea-level rise projection and storm surge scenarios for several epochs up to the year 2100.

Vertical velocity is calculated by combining Interferometric synthetic aperture radar (InSAR) and Global Positioning System (GPS) data, including 101 ascending L-band ALOS SAR images from 8 overlapping frames from 2007-2011, 108 descending C-band Sentinel-1A SAR images from 2 overlapping frames from 2016-2019, and measurements of 500+ GPS stations from the PBO network by the University of Nevada. The satellite line of sight data is projected to vertical using satellite unit vector geometry and then from a local to IGS14 global reference frame. Texas Natural Resources Information System supplies 50cm resolution Lidar data and we resample both vertical velocities and Lidar onto a 1m x 1m grid. By the year 2100, over 76 km² are projected to subside below sea level. The subsided elevation models are then subjected to multiple inundation and flooding scenarios. First, sea-level rise projections are based on scenarios assuming a range of possible radiative forcing values related to greenhouse gas concentrations from the Representative Concentration Pathways (RCP) adopted by the Intergovernmental Panel on Climate Change (IPCC). Using local projections for Galveston up to the year 2100, we examine 2-sigma confidence ranges for RCP2.6, RCP4.5, RCP6, and RCP8.5. Next, we include four simplified storm surge scenarios based on complex coastline modeling of various cyclone landfall locations and intensities. The multiple combinations of subsidence with sea-level rise and storm surges of different severities predict a range of flood and inundation extents that can inform future flood resilience plans.

Miller, M. M., & Shirzaei, M. (2019). Land subsidence in Houston correlated with flooding from Hurricane Harvey. Remote Sensing of Environment, 225, 368–378.