Summary

Land subsidence in metropolitan areas is a major human-induced geological hazard that affects buildings and urban infrastructure and results in severe economical consequences for both individuals and local government administrations.

Photos: (Hydrogeology Group, UNAM) Effects of the superficial faulting induced by differential subsidence in the metropolitan area of Mexico City.

In Mexico the intense water exploitation in urban areas has resulted in high subsidence rates and consequently increasing geological hazards. Mexico City, which is the second largest metropolitan in the world, subsidence rates exceed 370 mm/yr resulting in continuous structural damage to houses and infrastructure. In other cities in central Mexico, subsidence is at relatively lower levels, but still high enough (40-90 mm/yr) to cause significant surface faulting and induce structural damage to a large number of houses and urban infrastructure. These observed subsidence rates are induced by increasing water demands, rapid groundwater level drop and sediment consolidation occurring due to rapid growth of urban population and higher standard of living. The fast growth of the Mexican economy, specially on the more industrialized central and northern part of Mexico suggests that water demand will continue to increase, which will magnify the subsidence and the related hazard in several Mexican urban areas.

Figure 1: The development and livelihood of urban areas requires the use of water resources, of both surface water and groundwater. However, the lack of planning or excessive growth of urban areas creates a imbalance between the extraction of water from different water sources and natural recharge. All this changed the conditions of natural equilibrium, geomaterials suffer decompensation and subsequent mechanical rearrangement; the collapse or subsidence is the result of this realignment.