The land beneath many U.S. cities, such as New Orleans, New York City, Miami, and south San Francisco, is experiencing a concerning phenomenon known as land subsidence. This issue can have severe implications on the integrity of buildings and infrastructure within these urban areas. Furthermore, when combined with sea-level rise, land subsidence can lead to a significant increase in flooding occurrences. Recent research conducted by assistant professor Mehdi Nemati and his colleagues at the University of California, Riverside, sheds light on the financial burden that land subsidence places on U.S. homeowners. According to their findings, homeowners could potentially lose up to 6% of their property value due to land subsidence. In regions with higher rates of subsidence, this percentage can soar to a staggering 8.1%.
Causes of Land Subsidence
Both natural and man-made factors contribute to the occurrence of land subsidence in urban areas. As glaciers retreat from the U.S. and Canada, a “see-saw” effect is created, causing the land in the U.S. to sink while rising in Canada. Additionally, tectonic processes, such as earthquakes, play a role in inducing land subsidence. Professor Manoochehr Shirzaei from Virginia Tech highlights that earthquakes can lead to both land sinking and rising in various locations, illustrating the complexities of natural processes impacting land stability. Human activities, including groundwater extraction and urban development practices, also play a significant role in exacerbating land subsidence issues. The extraction of groundwater for drinking and other purposes causes the underlying land to compact, especially when combined with heavy building materials used in urban construction projects.
Implications for Homeowners and Infrastructure
The effects of land subsidence are visible to homeowners through structural problems in their properties and can have indirect consequences on the local economy. Standard homeowners insurance typically does not cover damages related to land subsidence, leaving homeowners vulnerable to costly repairs. Moreover, the stability of infrastructure, such as rail lines, bridges, and roads, is compromised by shifting land. This poses a serious safety risk to the public and can lead to significant financial investments to reinforce and repair infrastructure to withstand land subsidence impacts. Unfortunately, many existing urban infrastructures were not designed to accommodate changing land conditions, further complicating the challenge of addressing this issue effectively.
The rising issue of land subsidence in U.S. cities presents a multifaceted challenge that requires proactive and coordinated efforts from policymakers, urban planners, and residents to mitigate its adverse impacts. By addressing the root causes of land subsidence through sustainable urban development practices, responsible groundwater management, and strategic infrastructure planning, cities can better prepare themselves for the threats posed by sinking land. Awareness of the implications of land subsidence on property values, public safety, and economic stability is essential in fostering resilient and sustainable urban environments in the face of this growing environmental concern.