Water Resources Research Act Program

Details for Project ID 2009ND192B

Regional Flood Frequency Analysis in the Missouri River Basin Based on L-moments and GLS Regression

Institute: North Dakota
Year Established: 2009 Start Date: 2009-03-01 End Date: 2010-02-28
Total Federal Funds: $4,000 Total Non-Federal Funds: $8,000

Principal Investigators: Yeo Lim

Project Summary: The Interagency Advisory Committee on Water Data of the United States Geological Survey published Bulletin 17B Guidelines for Determining Flood Flow Frequency, which sets out the methods to be used for finding extreme event flows for all streams in the United States. The Bulletin has served its purpose extremely well since its final revision in 1982, however; many in the academic community believe that the time has come for updates using todays technology and modern statistical methods. Many researchers have criticized the fixing of a single distribution for the sake of uniformity in flood distributions. Bulletin 17B also employs a generalized skew map that may be used for the calculation of weighted skew. The most recent revision of this skew data was published in 1976 lending to inaccuracy due to outdated data. The annual maximum floods can be the result of snow melt runoff rather than rain dominant annual maximums of other years. This was found to be particularly true for northern regions such as North Dakota and the Missouri River Basin. Such series are classed as mixed populations and require more elaborate analysis. The use of L-moments is proposed here to improve the situation concentrating on its improvements by being flexible to the use of whichever distribution most closely reflects that of the collected data set. There is an urgent need to update these procedures using modern statistical methods. This study will provide a comprehensive set of L-moment index flood growth curves and Qmean regression equations for all homogeneous regions throughout the entire Missouri River Basin, which includes most of the state of North Dakota as well as several neighboring states. It should be noted that the researcher is holding open the option of limiting this study to only include the Upper Missouri River basin if it is thought that time constraints and volume of data conflict. The study will also provide a good alternative and comparison to the current Bulletin 17B procedures.