Improvement of Nonlinear Rainfall-Runoff Model

Water resources engineers have long been aware that the linear assumption of unit hydrograph models produces poor results in some basins. The Amorocho-Branstetter nonlinear model is an alternative to unit hydrograph models in these instances, but has not been as popular, perhaps because the user had to determine the parameters by trial-and-error, thereby needing to understand more of the mathematical background of the model than desirable. Moreover, in many instances, the trial-and-error procedure was expensive and tedious. This paper presents a way to efficiently calculate the three main model parameters, memory, U, order, IORD, and truncation, M1 and M2. These calculations are programmed into the model so the user need not supply them.