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Evaluating Runoff Predictions from Rainfall Tables and Generalized Distribution Curves for EFH-2 and WinTR-20 in New York State

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2012 Dallas, Texas, July 29 - August 1, 2012  121338007.(doi:10.13031/2013.41859)
Authors:   Peter E Wright, Kimberly Junkins, John Patrick Hock, Michael Martin,, William H Merkel, Quan D Quan, Helen Fox Moody
Keywords:   WinTR-20, Return periods, Runoff, Distribution curves, EFH-2

Abstract: Predictions of extreme precipitation events are used in the design of conservation practices, erosion and sediment control structures, stormwater management, concentrated animal feeding operation regulations and in many other engineering structures involving hydrologic flows. The Northeast Regional Climate Center has updated and made available sound data that will assist in estimating expected extreme rainfall amounts under varying conditions. This data replaces the rainfall data set developed in the 1960s by adding 50 years of additional rainfall measurements. Gridded 1, 2, 5, 10, 25, 50, 100, 200 and 500-year return period precipitation amounts were computed for durations of 5, 10, 15, 30, and 60 minutes; 1, 2, 3, 6, 12 and 24 hours and 1, 2, 4, 7, 10 days. To utilize the NRCS runoff models, grid-specific 24-hour rainfall distribution curves were developed based on the interpolated daily and hourly return period precipitation amounts and region specific n-minute extreme precipitation ratios. These specific inputs can be used in WinTR-20 to predict the runoff amounts. Rainfall tables based on average extreme rainfalls for each county (or portions of a county when the amounts vary widely) and regional distribution curves based on the 25 year event are used to make simplified runoff predictions using the Engineering Field Handbook 2 (EFH-2) method. This paper compares and contrasts the results from each method making recommendations for policy within NYS on their use for various purposes.

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