Sensitivity analysis of hydrograph peak flows obtained by the SCS method in an urban watershed

Abstract

Estimates of maximum runoff flow are necessary for design of hydraulic works and hidrologycal model in urban and rural basins. The difficulty in applying the available procedures to calculate the variation of the surface runoff with time and its maximum value is in the choice of method. The investigation of a method that produces reliable estimates of maximum flow and surface flow hydrograph is of great interest, especially considering an area whose supply is almost exclusively from groundwater; studies of this type present a significant relevance to the recharge data of the aquifer. The objective of this paper is to evaluate the sensitivity of the maximum flood hydrographs obtained by the SCS (Soil Conservation Service) to the CN (Curve Number) and to the time of concentration in an urban micro basin located in the city of Juazeiro do Norte - CE. A total of 186 hydrographs of maximum flow rates were simulated from six scenarios of land use and occupation and values of time of concentration obtained by seven equations. The results indicated a high dependence on the maximum flow hydrographs to both parameters. In additional, the study revealed that the maximum flood in the basin analyzed is more sensitive to CN changes under the conditions of small time of concentration values.