Land Subsidence and Rebound in the Houston Ship Channel and Downtown Houston (2000-2018)

Widespread land subsidence resulting from the overexploitation of groundwater from the Gulf Coast Aquifer system has occurred and been observed in Greater Houston, TX for nearly a century. Extraction of groundwater can generate permanent land subsidence by causing the inelastic compaction of susceptible aquifer systems, typically unconsolidated alluvial systems comprised of interbedded aquifer and aquitard material. Although land subsidence persists to some degree throughout a majority of Greater Houston, slight land rebound has been observed within Downtown Houston and the area along the Houston Ship Channel. The purpose of this study is to summarize ground deformation, sediment compaction, and groundwater level changes that have occurred within the area of observed land rebound from 2000-2018. Moreover, the relationship between ground deformation and groundwater levels is utilized to estimate local preconsolidation heads. Global Positioning System (GPS) and borehole extensometer observations indicate that land rebound began in the region starting from 2001-2004 and that current rates of uplift range from ~0.6-4.0 mm/year. Borehole extensometer observations and seasonal modeling of GPS displacement and groundwater level time-series reveal that sediment compaction was widely confined within the Chicot aquifer in the area of observed land rebound. Preconsolidation head levels are considered to coincide with the termination of inelastic compaction and the onset of land rebound. Estimated preconsolidation heads for Downtown Houston and the Houston Ship Channel fall between 25-65 meters (Chicot) and 30-70 meters (Evangeline) below the land surface. The results from this study are important for understanding the mechanism of groundwater-withdrawal-induced land subsidence and for managing groundwater resources in the north and western parts of Greater Houston, where moderate to rapid land subsidence (~1-3 cm/year) is ongoing.