The Geophysical, Anthropogenic, and Social Dimensions of Delta Risk: Estimating Contemporary and Future Risks at the Global Scale

Abstract:

Deltas are highly sensitive to increasing risks arising from local human
activities, land subsidence, regional water management, global sea-level rise,
and climate extremes. We extended a delta risk framework to include the impact
of relative sea-level rise on exposure to flood conditions. We apply this
framework to an integrated set of global environmental, geophysical, and social
indicators over 48 major deltas to quantify how delta flood risk due to extreme
events is changing over time. Although geophysical and relative sea-level rise
derived risks are distributed across all levels of economic development, wealthy
countries effectively limit their present-day threat by gross domestic
product–enabled infrastructure and coastal defense investments. However, when
investments do not address the long-term drivers of land subsidence and relative
sea-level rise, overall risk can be very sensitive to changes in protective
capability. For instance, we show how in an energy-constrained future scenario,
such protections will probably prove to be unsustainable, raising relative risks
by four to eight times in the Mississippi and Rhine deltas and by one-and-a-half
to four times in the Chao Phraya and Yangtze deltas. The current emphasis on
short-term solutions on the world’s deltas will greatly constrain options for
designing sustainable solutions in the long term.