Projected Changes in Flood Peak Discharge Across Iowa: A Flood Frequency Perspective - 20-SPR2-002

(2023) Projected Changes in Flood Peak Discharge Across Iowa: A Flood Frequency Perspective - 20-SPR2-002. Transportation, Department of

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Abstract

Numerous modeling studies point to an intensification of the hydrological cycle under projected climate warming, with increasing frequency of extreme events, including heavy rainfall and flooding. So, what would projected changes in flooding mean for the Iowa Department of Transportation (IDOT) and the bridges and structures that constitute Iowa’s highway system? How resilient are these highway structures to different climate warming scenarios? Addressing these questions requires flood frequency analysis. The current methodology relies on the guidelines by Bulletin 17C. However, issues related to regionalization of at-site estimates as well as accounting for the projected changes in the climate system have received little attention despite the potentially large impacts, including to the IDOT’s infrastructure. Here the authors have focused on the examination of the projected changes in flooding across Iowa using the hydrologic model developed by the Iowa Flood Center (IFC). The focus is on high-resolution and downscaled outputs from CMIP5 (Fifth Coupled Model Intercomparison Project) and CMIP6, and different scenarios. The results point to an increase in flood hazard across much of state, especially for high emission scenarios and towards the end of the 21st century. Moreover, the authors have developed a web interface - the Iowa Flood Frequency and Projections tool (IFFP) - that provides projections of flooding to the end of the twenty first century at any river reaches in the State of Iowa.