Land Rebound and Preconsolidation Head in the Houston Ship Channel Area

Widespread land subsidence resulting from excessive groundwater pumping has occurred in and around Houston, Texas for nearly a century. Hydraulic heads in much of the region have been recovering steadily since the mid-1970s following the efforts of local organizations to regulate groundwater production. In the past 15-years, subsidence in the vicinity of the Houston Ship Channel area has arrested and given way to slight land rebound occurring at a rate mostly between 0.2 and 1 centimeter per year. To better understand the change from land subsidence to land rebound, preconsolidation heads, which indicate the threshold between elastic and inelastic deformation, should be taken into consideration. In areas experiencing land subsidence, subsidence will tend to continue, even after groundwater recharge has begun, until hydraulic heads rise to the preconsolidation level. Knowledge of current preconsolidation heads in a region experiencing ground deformation can help to provide important detail about the relationship between groundwater levels, change in groundwater levels, and ground-deformation trends in that region. An estimate of current preconsolidation head levels in the region of rebound was made by examining available subsidence and compaction data against groundwater data measured in the Chicot and Evangeline aquifers. Preconsolidation head levels were considered to coincide with the termination of inelastic compaction and the onset of rebound in the ship channel area. Measurements in the Chicot aquifer were ultimately used in the estimation as historical compaction in the ship channel area likely occurred mostly within its extent. The estimated preconsolidation head levels are between 25 and 65 meters below the land surface and fall closely in line with estimates made in previous work. Rapid land subsidence would therefore not be expected to reoccur in the region unless hydraulic heads in the Chicot aquifer were to again fall below this estimated range of preconsolidation levels.Earth and Atmospheric Sciences, Department o