A simulation method for predicting hydrological effects of land-use changes
Thesis DisciplineCivil Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
A method was developed to predict the effects of land-use changes on flood hydrograph characteristics, especially the flood peak. It comprises a modified version of the Laurenson (1962, 1964) runoff routing model and employs a sensitivity analysis technique (Burton, 1969). The loss rate parameter in the model is altered to simulate land-use changes. With only the basic rainfall and stream flow data, the method permits an examination of the hydrological sensitivity of different sub-areas of a catchment to land-use changes. It therefore enables the designer to find that region of a catchment where a proposed land-use change would have the most beneficial effect on the flood hydrograph at the outlet. Before a fully quantitative prediction can be made a mathematical relationship between the loss rate parameter and the proposed land-use change is normally required. In this investigation a relationship was obtained for the exotic forest land use. A feature of the investigation was the improvement of the Laurenson model for reproducing flood hydrographs. The isochronal sub-area pattern of the Laurenson model was amended so that the model flow pattern more closely approximates the catchment drainage system. An optimisation procedure was also incorporated in the model for the purpose of deriving the optimum routing equation for the storm concerned. The modified model and the prediction method are demonstrated using the 780 square mile (2020 km²) Motueka catchment in New Zealand.