Comprehensive Review of Runoff Estimation by the Curve Number Method
Rainfall-runoff relationship is one of the most important phenomena in hydrologic design of hydrological structures and drainage systems. The estimation of runoff volume of a catchment is an important aspect in engineering planning, environmental impact assessment, flood forecasting and water balance calculations. There are basically two types of methods for the estimation of runoff namely the direct method and the indirect method. The direct method is based on the direct measurements while the other one is based on the equations. One of the indirect methods for the computation of runoff is the National Resource Conservation Service curve number method. This paper gives a review of the origin of the curve number method and development of the curve number equations. The Natural Resource Conservation Service curve number technique is a well-accepted tool for estimation of direct runoff from storm rainfall. CN model is used where constraints like slope, land cover, type of soil, area of watershed etc. are considered for runoff estimation.