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Directed: Assessing Flood Frequency in a Changing Climate

Summary:  Translate time-developing climate projections into hydrologic projections, and apply legacy procedures for flood frequency estimation in a moving-period fashion.

Contact:  David Raff, draff@usbr.gov 303-445-2461

Fiscal Years: 2008-2010

Research Question: 

  • How might we characterize changing flood frequency and flood risk possibilities in the context of time-developing climate projections? 

  • What are some of the analytical choices for conducting this analysis and how do these choices bear influenced on characterized changes in flood frequency?

Need and Benefit:

Flood safety is of the utmost concern for water resources management agencies charged with operating and maintaining reservoir systems. Risk evaluations guide design of infrastructure alterations or lead to potential changes in operations. Changes in climate may change the risk due to floods and therefore decisions to alter infrastructure with a life span of decades or longer may benefit from the use of climate projections as opposed to use of only historical observations.

This effort involves developing and demonstrating a framework that supports flood frequency evaluation within the context of downscaled climate projections, from simulated past to projected future.  The framework includes three core elements:

  • A rationale for selecting climate projections to represent available climate projections

  • Generation of runoff projections consistent with climate projections using a process-based hydrologic model and temporal disaggregation of monthly downscaled climate projections into 6-hourly weather forcings required by the hydrologic model

  • Analysis of flood frequency distributions based on runoff projection results

In addition to demonstrating the methodology, this paper also presents method choices under each analytical element, and the resulting implications to how flood frequencies are evaluated.

Partners:  Reclamation Dam Safety Office, U.S. Army Corps of Engineers

Keywords:  flood, climate change, hydrology model