Rainfall-runoff modelling in gauged and ungauged urban catchments using Urban Stormwater Model (USwM)
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Date
2009
Authors
Choong, Wee Kang
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Abstract
This research was carried out to enhance the stormwater modelling efficiency in terms of
model maintainability and improvement in ability for runoff prediction in urban catchments.
The work included rainfall-runoff analysis, site infiltration tests, redevelopment of Urban
Stormwater Model (USwM) and, finally model simulation using USwM. Two urban
catchments were used, the Sg. Kayu Ara for model calibration and validation and, Sg.
Kerayong catchment for runoff prediction. The rainfall-runoff relationship for the Sg. Kayu
Ara catchment was established as a linear equation, Runoff = 0.60 x Rainfall – 2.83, based
on 104 rainfall events. The 60% urban area and average catchment depression storage of
2.83mm indicated by the established equation was found consistent with the information
extracted from land use map. The results of infiltration tests showed that infiltration rates
vary greatly on sandy soil. The fitted Horton parameter values were 210 and 18mm/hr for
initial and final infiltration rate and 0.1955/minute for decay constant. Analysis of variance
indicated no significant difference between mean of fitted Horton parameters for dry and wet
sandy soil and, for the soil types of loamy sand and sand. Object-oriented Urban Stormwater
Model (USwM) was redeveloped using Visual C++ as the programming language. The work
removed snow and water quality components, two evaporation input options and one
optional input in Horton method. USwM was calibrated and validated in Sg. Kayu Ara
catchment using the formulated generic stormwater modelling procedures with the observed
records used as simulation target. The coefficients of determination (R²) from distributed
modelling were 0.83 and 0.90 for peak discharge and runoff volume. For runoff prediction at
Sg. Kerayong catchment, the R² of 0.72 for peak water level was obtained. The research goal
has been achieved with enhanced model maintainability using object-oriented technology
and improved ability for runoff prediction through the formulated generic stormwater
modelling procedure.
Description
PhD
Keywords
Civil Engineering , Rainfall-runoff , Urban Stormwater Model