| The principal objective of this dissertation research is to develop and apply a linear systems modeling tool for flood hydrograph and sediment transport analysis in Hawaii watersheds. According to the linear systems theory, system output function can be calculated by a convolution integration of the system's input function and impulse response function. The linear watershed system model developed by this research consists of two sub-models: a rainfall-runoff sub-model, and a sediment transport sub-model. For a rainfall-runoff sub-model, the input function is effective rainfall, the output function is direct runoff hydrograph, and the impulse response function is instantaneous unit hydrograph. For a sediment transport sub-model, the input function is effective sediment, the output function is pollutograph, and the impulse response function is instantaneous unit pollutograph.;The rainfall-runoff sub-model is developed by this research by modifying the modern unit hydrograph method which is the most popular analytical tool for flood hydrograph analysis. System parameterization is used so that the instantaneous unit hydrograph of a watershed system can be updated as watershed characteristics change overtime; thus, it removes one of the major weaknesses associated with the unit hydrograph method which assumes watershed systems are time-invariant. Another major accomplishment of this research is the derivation of a formula for better estimation of effective rainfall.;The sediment transport sub-model is developed by this research in parallel to the rainfall-runoff sub-model. In this research, techniques have been developed for the formulation and estimation of input function or effective sediment and impulse response function or instantaneous unit pollutograph. Similar to the rainfall-runoff sub-model, system parameterization is applied to remove the weakness due to time-invariant assumption.;The linear system watershed modeling tool developed by this research was applied successfully to selected Hawaii watersheds for flood hydrograph and sediment transport analysis. A comparative study was also conducted by using the modeling tool developed by this research and a popular watershed model or Hydrological Simulation Program FORTRAN (HSPF). Results of this comparative study suggest that with less parameters involved, a linear system model would provide better results than HSPF model with limited data available.;Keywords. Linear systems, watershed, flood hydrograph, pollutograph, effective rainfall, recession flow index, sediment transport, pollutant loading, non point source pollution. |
