Deep Uncertainty Surrounding Coastal Flood Risk Projections: A Case Study for New Orleans

• Published in: Earth's future Vol. 5; no. 10; pp. 1015 - 1026
• Main Authors: Wong, Tony E., Keller, Klaus
• Format: Journal Article
• Language: English
• Published: Hoboken, USA Wiley Periodicals, Inc 01-10-2017; John Wiley & Sons, Inc
• Subjects: Antarctic ice sheet; Case depth; Case studies; Coastal flooding; Coastal management; Coastal zone management; deep uncertainty; Disintegration; Distribution functions; Environmental risk; Extreme weather; Flood insurance; Flood management; Flood protection; Flood risk; Flooding; Floods; Global temperatures; Global warming; Measuring instruments; Probability distribution; Probability distribution functions; Radiative forcing; Risk; Risk management; scenarios; Sea level; Sea level changes; Sea level rise; Sensitivity analysis; Statistical analysis; Storm surges; Tidal waves; Uncertainty
• ISSN: 2328-4277; 2328-4277
• DOI: 10.1002/2017EF000607

Key Points
We characterize key deep uncertainties surrounding flood risk projections for a levee ring in New Orleans using 18 probabilistic scenarios
The levee system alone may provide flood protection between the 100‐ and 500‐year return period
Uncertainty in the storm surge distribution shape parameter is the primary driver of flood risk variability
Future sea‐level rise drives severe risks for many coastal communities. Strategies to manage these risks hinge on a sound characterization of the uncertainties. For example, recent studies suggest that large fractions of the Antarctic ice sheet (AIS) may rapidly disintegrate in response to rising global temperatures, leading to potentially several meters of sea‐level rise during the next few centuries. It is deeply uncertain, for example, whether such an AIS disintegration will be triggered, how much this would increase sea‐level rise, whether extreme storm surges intensify in a warming climate, or which emissions pathway future societies will choose. Here, we assess the impacts of these deep uncertainties on projected flooding probabilities for a levee ring in New Orleans, LA. We use 18 scenarios, presenting probabilistic projections within each one, to sample key deeply uncertain future projections of sea‐level rise, radiative forcing pathways, storm surge characterization, and contributions from rapid AIS mass loss. The implications of these deep uncertainties for projected flood risk are thus characterized by a set of 18 probability distribution functions. We use a global sensitivity analysis to assess which mechanisms contribute to uncertainty in projected flood risk over the course of a 50‐year design life. In line with previous work, we find that the uncertain storm surge drives the most substantial risk, followed by general AIS dynamics, in our simple model for future flood risk for New Orleans.