Subsidence

Hampton Roads has experienced one of the highest rates of relative sea level rise on the Atlantic coast over the past century. A study funded by NASA and CCRFR reveals that land in the metropolitan area is sinking at highly uneven rates, with a few trouble spots subsiding 7 to 10 times faster than the spatial average, with major differences in subsidence rates being observed only a few miles apart.

This rate of relative sea level rise results from a combination of land subsidence, which has long been known to be present in the region, and rising seas associated with global warming on long timescales and exacerbated by shifts in ocean dynamics on shorter timescales. An understanding of the current-day magnitude of each component is needed to create accurate projections of future relative sea level rise upon which to base planning efforts. The objective of the NASA study was to estimate the land component of relative sea level rise using interferometric synthetic aperture radar (InSAR) analysis applied to ALOS-1 synthetic aperture radar data acquired during 2007–2011 to generate high-spatial resolution (20–30 m) estimates of vertical land motion. Although these results are limited by the uncertainty associated with the small set of available historical SAR data, they highlight both localized rates of high subsidence and a significant spatial variability in subsidence, emphasizing the need for further measurement, which could be done with Sentinel-1 and NASA’s upcoming NISAR mission.