Coastal subsidence mapping with InSAR for sea level rise vulnerability mapping over Hampton Roads.

Hampton Roads is located within the southeastern corner of the state of Virginia, USA. This coastal inlet is predominantly urban and has the largest concentration of federal bodies and facilities of any metropolitan area in the world. This area is experiencing some of the highest rates of sea level rise in the USA, in part due to land subsidence related to compaction of aquifers within this region.

Ongoing monitoring of these trends is crucial for effective coastal risk management, particularly over sensitive and at-risk areas.

In collaboration with the National Oceanic and Atmospheric Administration (NOAA), the National Geodetic Survey, TRE ALTAMIRA conducted a study to identify surface deformation over Hampton Roads, covering July 2011 to August 2017. The data processed for the analysis comprised 130 synthetic aperture radar (SAR) images acquired by the Cosmo-SkyMed satellite.

A number of localized movement features, in addition to regional subsidence trends were detected with sub-millimetric precision from this InSAR processing, carried out using the SqueeSAR® algorithm. Results highlighted displacement trends in vulnerable areas, and within frequent flooding zones.

InSAR map over Hampton Roads East Ocean
Displacement measurements (top) were analysed side-by-side with NOAA’s Sea Level Rise Viewer to highlight areas particularly vulnerable to sea level rise. The example in the bottom portion of the figure sets the sea level rise to three feet (light blue).

Beyond the regional subsidence trends found throughout the Hampton Roads area, localised subsidence features were observed over airports, railways, elevated structures, roadways, and buildings. Maximum settlement rates within the full data set were observed along the Craney Island berms, reaching minimums of -1.93 inches/year (-48.9 mm/year). Detailed time series of motion show that the displacement is linear and rapid during the 6-year study.

InSAR study-close up of Craney-Island in Hampton Roads
Subsidence results identified over Craney Island and surrounding area.
Time Series graph
Average time series generated from measurement points identified along the berm of Craney Island.

The results of our study were presented to the community at the Hampton Roads Adaptation Forum and can be accessed here.