Disappearing cities on US coasts.

Area of Science:

• Earth and Environmental Sciences
• Geophysics
• Urban Planning

Background:

• Sea level rise projections indicate 0.25-0.3m rise by 2050 for US coastlines.
• Coastal subsidence, or land sinking, is an underrepresented factor in current coastal management and urban planning.
• This land sinking can significantly worsen the impacts of sea level rise, increasing flood and inundation risks.

Purpose of the Study:

• To quantify potential inundated areas in 32 major US coastal cities by 2050.
• To integrate high-resolution vertical land motion and elevation data with sea level rise projections.
• To highlight the threat posed by coastal subsidence to urban populations and properties.

Main Methods:

• Combined high-resolution vertical land motion (land elevation changes) and elevation datasets.
• Utilized sea level rise projections for the year 2050.
• Quantified potential inundated land area, population, and property exposure in 32 US coastal cities.

Main Results:

• Between 1,006 and 1,389 km² of land area is threatened by relative sea level rise by 2050, even with existing coastal defenses.
• An estimated 55,000-273,000 people and 31,000-171,000 properties face risks.
• Analysis indicates that neglecting spatially variable land subsidence leads to inaccurate exposure projections.

Conclusions:

• Failure to account for coastal subsidence results in underestimated flood risks for US coastal cities.
• The scale of the adaptation challenge posed by relative sea level rise is currently not fully appreciated in most US coastal cities.
• Accurate urban planning and coastal management require the integration of land subsidence data into sea level rise impact assessments.