Flood Frequency Variability on Seasonal to Multidecadal Time Scales in the Western US and Implications for Infrastructure Planning

Project ID: 1916
Principal Investigator: Subhrendu Gangopadhyay
Research Topic: Managing Hydrologic Events
Priority Area Assignments: 2013 (Climate Change and Variability Research), 2014 (Climate Change and Variability Research), 2015 (Climate Change and Variability Research)
Funded Fiscal Years: 2013, 2014 and 2015
Keywords: flood frequency, climate, extreme value analysis, infrastructure planning

Research Question

1. How are extreme flooding events manifested? Specifically, what atmospheric and hydrologic ingredients conspire to produce extreme flood events at short (seasonal and below) and long (multidecadal) time scales?

2. How can this understanding be employed to model flood frequency in space and time, and under a changing climate?

3. What are the implications for long-term infrastructure planning (e.g., dam safety, levee protection, etc.)and management?

Need and Benefit

The proposed research addresses Priority Area 4.03 described in the long-term user needs document (LTDOC).

Existing methods of flood-risk estimation is based on flood-frequency methods that assume a stationary climate. Methods of non-stationary extreme value space-time analysis and availability of tools to apply EVA methods efficiently is relatively new (e.g., Coles, 2001; Gilleland and Katz, 2011). Availability of such EVA tools makes it feasible to analyze climate projections of extreme events (floods) probabilistically. Reclamation is being asked in several of its basin studies (WaterSMART Basin Studies Program) questions on flood risk to existing infrastructure from a changing climate. For example, will floods become more severe and threaten flood infrastructure under climate change? Are dams sufficiently sized for the 200 year storm or does the risk level increase under climate change?

The proposed research is aimed to develop an approach to respond to questions above, and meets the needs identified in LTDOC gap 4.03 - method and basis for estimating extreme hydrologic event possibilities possibilities in a changing climate. Implicit in this gap is the need for developing a long-lead forecasting tool that can be used to predict extreme events (floods) under a changing climate. This project will accomplish this first by understanding the space-time manifestation of extreme flooding events, and subsequently apply nonstationary flood-frequency analysis in a forecasting context with large-scale climate drivers to model flood frequency in space and time.

This research will help to develop:
(1) Methods to perform nonstationary space-time flood frequency analysis.
(2) Understanding of flood-frequency under a changing climate.
(3) Forecasting tool to predict flood events under climate change.
(4) Characterization of infrastructure risk from floods under climate change.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Forecasting Extreme Flooding Events (final, PDF, 651KB)
By Subhrendu Gangopadhyay (PI), Cameron Bracken (PR)
Publication completed on September 30, 2016

This bulletin summarizes the research results and potential application to Reclamation's mission.

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Last Updated: 6/22/20