Across the United States, the ground beneath many cities is slowly sinking — in some cases, rapidly. Soil subsidence is no longer a regional anomaly confined to coastal zones or floodplains. It is a national infrastructure challenge in growing population centers, with several implications for facility owners, design professionals and contractors responsible for the long-term performance of buildings and sites.
A recent peer-reviewed study published in Nature Cities has drawn renewed attention to the issue by identifying widespread land subsidence across major metropolitan areas. While Houston, Dallas and Fort Worth ranked among the most affected, similar trends are playing out nationwide from California’s Central Valley and the Mississippi Delta to parts of the Midwest and the Eastern Seaboard.
For facility owners and contractors, even small amounts of vertical ground movement matter. Subsidence rates of just a few millimeters per year can compound over time, stressing foundations, destabilizing slopes, accelerating erosion and shortening the expected service life of infrastructure. When widespread subsidence intersects with local topography and drainage patterns, the risks of slope instability and erosion are greatly amplified.
Understanding the way soil subsidence, slope stability and erosion interact, as well as strategies to mitigate them, should be a core competency for anyone involved in site development, building construction and facilities maintenance.
Soil subsidence refers to the gradual sinking or settlement of the ground surface. While it often occurs slowly, the cumulative effects can be severe, particularly when subsidence is uneven across a site. The causes of subsidence vary by region, but two drivers dominate nationwide:
Groundwater extraction. The most significant contributor to land subsidence is the drawdown of groundwater aquifers. When water is pumped from aquifers, the pore pressure that once provided buoyancy to the overlying soils decreases. Fine-grained soils, particularly silts and clays, compress when this support is removed. Such soil consolidation results in permanent settlement. This process is well documented in agricultural regions and in rapidly urbanizing areas where municipalities rely heavily on groundwater for potable water supply, especially during drier periods.
Urban development and structural loading. The weight of buildings, pavement and infrastructure adds stress to underlying soils, accelerating consolidation, especially in areas with compressible soils. This loading effect is not limited to high-rise construction. Even low-rise industrial buildings, parking structures and roadway embankments can induce settlement if soil conditions are unfavorable. As cities densify and redevelop older sites, cumulative loading from decades of construction can push soils beyond their designed long-term capacities. The urban sprawl of new infrastructure across areas where groundwater levels are being reduced can exacerbate the issue across the larger region.
Not all soils respond the same way to loading, moisture or environmental change. Much of the U.S. is underlain by clay-rich soils that are particularly susceptible to movement.
Expansive clays. Expansive clays swell when wet and shrink when dry. These volume changes can exert significant forces on foundations, slabs, pavements and retaining structures. Regions with pronounced wet-dry cycles — including much of the South, Midwest and Plains states — experience repeated seasonal soil movement in addition to long-term subsidence.
Alluvial and coastal deposits. River valleys, deltas and coastal plains often consist of loose sediments that are prone to consolidation. These soils might appear stable initially, but they can compress significantly under sustained loading or groundwater drawdown. These areas are also very sensitive to water-level fluctuations, which can affect soil behavior.
Fill materials. Urban development frequently relies on engineered fill to reshape sites. Poorly compacted or improperly placed fill can settle unevenly, creating long-term maintenance and liability concerns.
Understanding site-specific soil behavior is essential, particularly as climate variability intensifies moisture fluctuations and rainfall extremes. For these reasons, it is important to provide adequate drainage and ensure slope stability, especially for sites where the existing topography has been significantly altered.
While subsidence itself is often gradual, climate-driven events can trigger sudden failures:
Zachary Henrichs, M.S., P.E., DFE, is the director of civil engineering with Knott Laboratory, a forensic engineering and visualization firm.
Soil Subsidence: What Building Owners Need To Know
