I just got word yesterday that I am to present at the 2010 WRRI Annual Conference at the McKimmon Center. I am to present at session 4B: Stormwater Management II on Wednesday, March 31st. The presentation will be entitled “A Comparison of Methods for Determining Peak Discharge in Small Watersheds at Selected USGS-gaged Locations: An Evaluation of the NCDOT Method”. The abstract is as follows:
The North Carolina Department of Transportation (NCDOT) uses a method for determining peak discharges in small watersheds (< 1 mi2) that is used nowhere else. The method involves the use of a series of charts that the NCDOT published in January 1973. The origins of the charts appear to be unknown (Genereaux 2002) and the accuracy relatively untested. The author became aware of these charts when a former colleague was in a dispute regarding the design of a culvert. He had sized it using a peak flow developed using the Hydrologic Engineering Center – Hydrologic Modeling System (HEC-HMS) and Soil Conservation Service (SCS) methods while the roadway designer had found that the culvert could be reduced in size and expense if one were to use the NCDOT charts instead, which gave a lower flow rate. The incident highlighted the need to understand the strengths and weaknesses of a particular hydrologic method in order to determine the appropriateness of its use.
In this presentation, a comparison is to be made between the NCDOT method, the Rational method, and the use of U.S. Geological Survey (USGS) regression equations in determining the peak discharges for the 5, 10, 25, and 100-year events. These discharges are to be determined at locations, both urban and rural, that have been previously gaged by the USGS and used for development in their regression equations. Discharge estimates are to be made using data available from the USGS reports and National Oceanic and Atmospheric Administration (NOAA) Atlas 14. These estimates are to be compared with those developed by USGS using statistical analysis of the gage data that was collected at each location. By comparison of these various estimates, it is hoped to demonstrate when each method may reasonably be used, which method is preferable, and what kind of accuracy can be expected.
Update: The presentation can be found here: 2010 WRRI Presentation.
Tags: civil engineering, hydrology, NCDOT, USGS, WRRI
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