Land subsidence increases the area in the Texas Coastal Zone which will be inundated by marine waters from hurricane flooding. Storm surge from a Carla-sized hurricane in 1976 would flood at least 25 square miles more land than Hurricane Carla did in 1961.

Land subsidence in Harris and Galveston Counties results primarily from ground-water production. The two-county area is interlaced with active surface faults with topographic escarpments and surface faults with no topographic escarpments that control drainage patterns and create subtle photographic linear patterns. Ground-water production activates these faults by differential compaction of the aquifer. The faults appear to be partial hydrologic barriers that compartmentalize land subsidence into several individual basins.