ACCURACY OF FLOOD ESTIMATION

In this study research is performed into the accuracy of flood estimation. In particular the rivers on the island of Java are considered. For these distinctive rivers, the GAMA I unit hydrograph theory was developed (Sri Harto 1985) for flood estimation. The GAMA theory defines 3 basic characteristics to represent a unit hydrograph; time of rise (time from the beginning of the storm to the time of peak discharge), peak discharge and base time (total time of run off). For these characteristics, relationships were derived by meàns of regression analysis using measured data of floods and related catchment characteris-tics. In this study the GAMA equations are again derived by means of a program (REGR-ES) including the calculation of the standard deviations and the correlations of the regression coefficients. These indicate the accuracy of the model. To include the inaccuracy of the input data a program (SIMCO) is constructed in which the input data (measurements) are extended with stochastic features. It is assumed that all data are normally distributed. A simulation is performed based on the Monte Carlo simulation technique to derive a set of 150 equations for each GAMA equation. The standard deviation