Description of Study Area

Tutorial 2 discussed surface drainage hydraulics of an urban catchment having an area of 48.79 acres as shown in Figure 2.2. Simulation with 2-year, 10-year, and 100-year design storms under different routing methods showed a significant increase in total runoff as well as in peak outflow compared to those of pre-developed conditions.

In this Tutorial, the same site (with all properties obtained from Tutorial 2) has been analyzed, and a detention pond is designed to control the excess peak in the outflow. Under the previously mentioned three storm events, the dynamic wave routing method has been used to determine the resulting runoff. The designed pond is proposed at the outfall location of the entire catchment. Through the outfall, the water will be released into the downstream receiving channel in a regulated manner.

The runoff results from Tutorial 01 and Tutorial 02 will be required to compare the system behavior before and after implementation of the design pond. Following Table 2.2 lists the model generated summary obtained from those Tutorials.

Table 2.2 : Runoff Summary Under Pre- and Post-Developed Conditions

The proposed detention pond has been represented by a storage unit SU1 in Tutorial 03. It has been modeled with three orifices and one weir to regulate the discharge. Besides, to accurately represent detention pond with the system, some additional junctions and conduits are provided. Details on the model network representation in GeoSWMM have been described in Model Setup. Table 2.3 lists the physical element quantity summary used in this Tutorial.

Table 2.3 : Network Object Quantity Summary with Proposed Detention Pond