The Effect of Inflection Angle and Relative Location on Runoff Curve Numbers from Zero-Order Watersheds

Fennessey, Lawrence A. J.; Hamlett, J. M.; Miller, Arthur C.

doi:10.1061/40583(275)47

Cited by 5 publications

(2 citation statements)

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“…Unfortunately, the curve number has been used for over 40 years with no significant changes, and few if any hydrologists would feel comfortable making curve number modifications beyond the range provided in the array table. However, Fennessey (2000) showed that the use of nontraditional topographic parameters could consistently explain a large percentage of the curve number variability seen in this study. Therefore, improvements to the existing CN array tables are possible; however, scientists must first reemphasize the accuracy of standard hydrologic models in research projects.…”

Section: Discussionmentioning

confidence: 54%

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ACCURACY AND PRECISION OF NRCS MODELS FOR SMALL WATERSHEDS¹

Fennessey¹,

Miller²,

Hamlett

2001

J American Water Resour Assoc

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In the last 30 years, the National Resource Conservation Service's TR‐55 and TR‐20 models have seen a dramatic increase in use for stormwater management purposes. This paper reviews some of the data that were originally used to develop these models and tests how well the models estimate annual series peak runoff rates for the same watersheds using longer historical data record lengths. The paper also explores differences between TR‐55 and TR‐20 peak runoff rate estimates and time of concentration methods. It was found that of the 37 watersheds tested, 25 were either over‐ or under‐predicting the actual historical watershed runoff rates by more than 30 percent. The results of this study indicate that these NRCS models should not be used to model small wooded watersheds less than 20 acres. This would be especially true if the watershed consisted of an area without a clearly defined outlet channel. This study also supports the need for regulators to allow educated hydrologists to alter pre‐packaged model parameters or results more easily than is currently permitted.

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Section: Discussionmentioning

confidence: 54%

“…However, several of the watersheds with partial series data were tested in an identical manner and produced similar results. Additionally, Fennessey (2000) showed that poor peak runoff estimates have a greater affect on the annual than the partial series following development.…”

Section: Methodology Used For Evaluationmentioning

confidence: 99%