Regional Hydrological Modeling of City of Tshwane Municipality using VisualSWMM
In order to develop an integrated catchment management plan for present and future development scenarios, the City of Tshwane Metropolitan Municipality (CTMM), situated in Gauteng province, South Africa, required integrated data on runoff peaks and volumes along all its major watercourses amounting to approximately 1400 km. This is focussed towards improving the planning and management of stormwater drainage systems in all catchments within its area of jurisdiction.
CTMM thus commissioned SRK Consulting (Pty) Ltd to compile a regional hydrological model of all its major watercourses as well as a river referencing system (RRS) and stormwater management information system (SMIS) to aid in managing the data.
The main objectives of the project can be summarised as follows:
1. review all available data (rainfall, runoff, catchment, landuse);
2. define the locality and nature of existing major drainage systems;
3. establish integrated intensity-duration-frequency relationships;
4. establish integrated design runoff hydrographs along major drainage systems and watercourses;
5. establish a RRS giving digital and visual information of all existing floodline data, scanned images, spatial and numeric data; and
6. compile a SMIS for easy access and queries of the data.
This chapter presents the derivation of the CTMM hydrological model generated in VisualSWMM covering an area of approximately 2300 km2. It describes a generic approach followed towards deriving a master drainage plan including data collection, catchment and watercourse delineation, rainfall analysis and the generation of the hydrological model, including calibration and verification, to be used as decision support for catchment management.
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