Methods are provided to estimate the magnitude and frequency of floods on natural North Carolina streams with drainage areas greater than 0.5 square mile (1.3 square kilometers). For 257 gaged sites, the magnitudes of floods having recurrence intervals from 2 to 100 years are provided in tables. For ungaged sites, equations, graphs, and maps allow estimation of flood magnitudes. Multiple regression techniques were used to define the relation between flood peaks and seven basin and climatic variables. Drainage area is the most significant variable. Inclusion of the other six variables reduced the standard error of estimate less than 4 percent. Regression equations gave consistently different results for stations in the Coastal Plain than for stations in the mountains and Piedmont. Accordingly, stations were divided into two groups and estimating equations were developed for each geographic area.
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Magnitude and frequency of floods in North Carolina, technique for estimating the magnitude and frequency of floods on natural streams in North Carolina