Abstract
Flooding is a prevalent natural disaster with both short and long-term social, economic, and infrastructure impacts. Changes in intensity and frequency of precipitation (including rain, snow, and rain-on-snow) events create challenges for the planning and management of resilient infrastructure and communities. While there is general acknowledgment that new infrastructure design should account for future climate change, no clear methods or actionable information are available to community planners and designers to ensure resilient designs considering an uncertain climate future. This research demonstrates an approach for an integrated, multi-model, and multi-scale simulation to evaluate future flood impacts. This research used regional climate projections to drive high-resolution hydrology and flood models to evaluate social, economic, and infrastructure resilience for the Snohomish Watershed, WA, USA. Using the proposed integrated modeling approach, the peaks of precipitation and streamflows were found to shift from spring and summer to the earlier winter season. Moreover, clear non-stationarities in future flood risk were discovered under various climate scenarios. This research provides a clear approach for the incorporation of climate science in flood resilience analysis and to also provides actionable information relative to the frequency and intensity of future precipitation events.
Highlights
Extreme flooding has been observed to become more prevalent and is expected to worsen with a changing climate considering the potential for increased precipitation in regions of the United States [1].Traditional approaches used for designing flood mitigation strategies or assessing flood risk have assumed a stationary climate [2], but it is increasingly important to consider changes in magnitude and frequency extreme events and include future climate scenarios in design [3].In many cases, the standards currently used in flood mitigation design using stationary climate assumptions are no longer sufficiently conservative assumptions [1]
It is noted that it may be more appropriate to include statistical approaches that account for the inherent non-stationarity that exists in the data. While this is a recognized limitation of utilizing the previously described approach, we demonstrate the use of the approach in this research because the Bulletin 17C method is the currently accepted approach in the United States flood risk management standard
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Summary
The standards currently used in flood mitigation design using stationary climate assumptions (for example, the historical 100-year return period) are no longer sufficiently conservative assumptions [1]. In 2015, a U.S Presidential Executive Order (13,690) mandated changes in the federal flood risk management standard. This order gives agencies the flexibility to either (1) use data and methods informed by best-available, actionable climate science, (2) build two feet above the 100-year flood elevation for standard projects or three feet above for critical buildings, or (3) build to the 500-year flood elevation. Approaches that explicitly consider future climate scenarios are needed in
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