Special Collection on the Curve Number Method in the 21st Century

Guest Editor: David A. Chin, Ph.D., P.E., BCEE, F.ASCE

The standard curve-number method in use today is essentially unchanged from its original one-parameter empirical form developed in the 1950's by the U.S. Department of Agriculture's Soil Conservation Service, subsequently renamed as the Natural Resources Conservation Service (NRCS). Despite substantial advances in the understanding of rainfall-runoff hydrology over the past 70 years, the curve-number method endures primarily because of its endorsement by the NRCS. Independent research done outside of the NRCS indicate that there are serious technical concerns about the adequacy of the curve-number method, which include neglecting the effect of the temporal distribution rainfall, neglecting the rainfall duration, and neglecting the functional dependence of the curve number on the rainfall amount. These issues are directly addressed in three papers included in this special collection, with a fourth paper addressing the issue of separating surface runoff from baseflow, which is fundamental to testing the performance of the curve-number method using field measurements.