STUDY OF SUBSIDENCE IN SOUTH MONTGOMERY, WEST CHAMBERS, AND NORTH AND WEST HARRIS COUNTIES FROM 2016 TO 2020

Subsidence, the sinking of the land surface due to underground movement, has been occurring in south Montgomery County, west Chambers County, and north and west areas of Harris County, Texas, USA. In Harris County, subsidence is primarily from groundwater extraction from the Chicot and Evangeline aquifers. Other factors such as the presence of faults in Harris County and petroleum extraction in Montgomery, Chambers, and Harris counties may contribute to the land subsidence. This work uses multi-temporal interferometric synthetic aperture radar (InSAR) from 2016 to 2020 and GPS data to measure ground deformation and map subsidence rates. For the InSAR data, subsidence rates of around -2 cm/yr and higher were observed in the Katy area. The GPS stations in the north and west Harris County area also recorded yearly subsidence rates of approximately -1.2 to -2 cm/yr or higher. All subsidence rates were then compared to the Evangeline and Chicot aquifers’ water levels and the locations of faults and oil and gas wells. Subsidence rates in the north to west Harris County have remained relatively high in recent years compared to the rest of the counties. The effects of petroleum extraction and fault motion along faults on subsidence in Harris County appear to have little to no impact on overall subsidence. In Montgomery County, groundwater extraction is the primary cause of subsidence. Recent decreases in groundwater withdrawal in Montgomery County through positive changes in groundwater elevation allow for smaller subsidence values. For Chambers County, further research will be necessary to conclude the causes of subsidence and their level of impact.