Note: There are Three Types of Surfaces in each Subcatchment of SWMM 5. The overall depth in a subcatchment is the weighted average of the impervious without depression storage area, the impervious with depression storage area and the pervious area depth. The depths on each type of area are independent of each other.
Figure 1: The processes that occur on each type of Subcatchment Area.
Figure 2: The three independent Depths on a Subcatchment. The SWMM 5 reported Depth is the weighted average of the three depths.