About this Application Manual

This manual has been prepared to serve as one of the practical application guides for modelers; provided that they have already acquired the basics of hydrology, storm water management modeling and on how GeoSWMM’s hydraulic elements and flow routing methods are used to model a surface drainage system. Especially they must know how to develop a GeoSWMM model using GIS data, to set simulation options and prepare model input data in ArcGIS Pro, and to run simulation and interpret model results under different scenarios. Readers are recommended to keep GeoSWMM User's Manual aside in case they face difficulties during model building and simulation process. The User's Manual elaborately discusses working with a GeoSWMM model and its different settings.

The previous Tutorial, Tutorial 02 discussed the effect of different channel routing methods on the surface runoff generated from a developed site. The results were compared with no-routing scenario and with the undeveloped site scenario. Developed scenario resulted in a significant increase in total runoff as well as in peak runoff flows.

In this Tutorial, the aim is to mitigate the increased runoff issue and to control the peak outflow by introducing a detention pond at the outlet of the entire catchment. The pond properties are defined, represented, designed and evaluated by using a storage unit, three orifices, and a transverse weir in the GeoSWMM model for Tutorial-Detention Pond Design. The detention pond serves as a multipurpose storage facility by detaining a Water Quality Capture Volume (WQCV) and limiting peak post-development runoff rates to their pre-development levels. Similar to the previous Tutorials, three storm events with return periods of 2-year, 10-year and 100-year have been analyzed here. In the next chapter, the worked-out Tutorial with illustrations is detailed.