A May 8th study published in the British journal Nature Cities charts the threat of sea level rise in major US cities. Boston is among the urban areas most susceptible to an “invisible threat, land subsidence.” According to the study authors, “Land subsidence is a slow-moving hazard with adverse environmental and socioeconomic consequences worldwide. While often considered solely a coastal hazard due to relative sea-level rise, subsidence also threatens inland urban areas, causing increased flood risks, structural damage and transportation disruptions.”
Like other cities in the study, Boston is sinking because of “massive ongoing groundwater extraction,” also known as land subsidence or vertical land motion. Over 72% of the city’s land area is sinking by up to 3 millimeters a year, and .3% is sinking even faster. That means that 525,231 people, or over 80% of the population, are vulnerable to the impacts of sinking in Boston. At critical risk is the structural integrity of buildings, roads, bridges, and dams. Early warning signs can be seen in cracks in walls and foundations, sloping floors, tilting fences and utility poles, and fire hydrants that stick out more than usual. Many of these danger signs are subtle and overlooked.
Two Texas cities, Houston and Forth Worth, show the greatest rates of subsidence (perhaps connected to underground pumping of oil and gas). In a coastal city like Boston, where sea-level rise is increasing dramatically, mitigation efforts are more urgent than ever. According to the study authors, “effective responses generally involve mitigation and adaptation, akin to strategies for addressing climate change… Ultimately, a robust and sustainable mitigation and adaptation framework should encompass continuous monitoring, stakeholder collaboration and flexible mitigation… Regardless of the pathway a city chooses, any effective mitigation and adaptation effort must be targeted to the dominant subsidence driver in each city, proportional to local vulnerabilities, and incorporate a multifaceted approach.”
Read the full research report.
