Deep groundwater extraction in aquifer with compressible fine-grained sediments results in release of water from the interbeds of the aquifer causing compaction and land subsidence. Coastal aquifers consist of multi-aquifer systems and are typically shallow unconfined aquifer separated from the confined aquifer below by a confining layer of clay. Large groundwater extraction for a long period of time in confined aquifer may results in change in effective stress in all the hydrogeologic layers – resulting in causing shallow land subsidence. This impact of groundwater extraction can be felt far away to an infrastructure – causing land subsidence and affecting structural foundations. Such impacts have been felt in large cities of the world such as in Jakarta, Indonesia, where land subsidence due to groundwater extraction caused significant loss to infrastructure to buildings. To further escalate the problem in coastal cities – land subsidence due to groundwater extraction accelerate sea level rise impacts. A three-dimensional groundwater model mimicking a coastal aquifer system such as in Georgia and Alabama with interbeds of fine sediments of multi-aquifer system with deep groundwater extraction for 50-year was simulated. The results show geostatic stress, fluid stress, and effective stress in unconfined/confining/confined layers changes along hydrogeologic layers and cause land subsidence and compaction. The results further support that risk to infrastructure foundations from large groundwater extraction even far away (could be in distance of kilometers) must be evaluated. Typically, this risk is not accounted in many of the world’s infrastructure projects.
