A 15-acre commercial site stormwater case study — worked rational-method pre/post-development peak flow, a triangular-hydrograph detention pond sizing estimate, an outlet control orifice calculation, and Manning's equation storm drain pipe sizing.
The project brief: a 15-acre commercial development replacing wooded/pasture land with roofs and pavement needs a complete stormwater system — detention limiting post-development peak discharge to the pre-development rate, a storm drain network, and an outlet control structure. Every downstream sizing decision in this project traces back to one rational-method calculation.
This module walks the whole design the way a practicing site civil engineer would: the pre- and post-development peak flow comparison that sets the allowable release rate, a triangular-hydrograph storage volume estimate for preliminary pond sizing, the orifice equation linking a target release rate to a physical outlet diameter, and a Manning's equation pipe-sizing decision for the storm drain trunk line. The full worked numbers, complete bill of materials, and finished design reasoning are part of the unlocked module below.