Subsidence Anomaly near Lynchburg, Texas

Extraction of ground water, oil, and gas has caused substantial subsidence in and around Houston, Texas. In places, subsidence up to approximately 3 m has been reported (e.g., White and Tremblay 1995). At a mid-channel island in the San Jacinto River, in the vicinity of Lynchburg, Texas, total subsidence between 1906 and 2000 is estimated to have exceeded 2.13 m (7 ft.). Examination of geomorphological evidence suggests that total subsidence for the San Jacinto River site could not have exceeded about 1.2 m (4 ft.).

The evidence involves the banks of a drainage channel in a crevasses splay that was surveyed in 1916, can be identified through time in a series of aerial photographs, and was partially resurveyed in 2003. Although there is some ambiguity in the exact location of some features, a subsidence estimate in excess of 2 m cannot be supported by the evolution of the landform. The size of the anomalous area is not known, nor is the reason for the discrepancy. The magnitude of the anomaly, however, should call into question the validity of the regional subsidence estimates.