Date of Award

1993

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Advisor

James F. Cruise

Abstract

Hydrologic modelling can be enhanced and improved through the utilization of a Geographic Information System (GIS). Information can be stored and analyzed by the tools available within a GIS to create a spatial database that realistically represents a watershed for hydrologic modelling. This study presents an approach whereby the data available in the GIS determine the modelling strategy. The soil, topography and land cover data for the watershed were analyzed with the spatial analysis tools of a GIS to determine the hydrologic response areas. The coordinate values that define the locations and boundaries of features in the GIS were used to identify which hydrologic response areas contributed to the flow at a particular inlet and to calculate the flow length for those areas. The coordinate values were also used to identify the storm drain that connected to the next downstream inlet and thereby permitted the discharge to be automatically routed downstream. The discharge was calculated using a modified version of the SCS runoff equations for the calculation of the effective rainfall and the kinematic wave routing formulation. The discharge for each hydrologic response area was combined and routed to determine the total discharge for two drainage areas within the watershed. The effects of spatial and scalar changes on the discharge were also investigated. The results show that when the resolution of the hydrologic response areas was changed it had very little impact on the discharge at the outlet of the two areas investigated. However, the results also indicated that when all the surfaces that contributed to the discharge at the inlet became impervious there was an increase in the peak discharge of 63.5% at the inlet and only 2.9% at the outlet. The discharge was also found to be sensitive to the surface roughness coefficient, as the investigation showed that the peak discharge from a pervious surface changed as much as 92.3% when the roughness coefficient was varied between 0.01 and 0.100. It was concluded that the inlet of a drainage network should be the location at which the effects of change on the discharge are evaluated.

Pages

203

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