But in a 2.1 km2 ultra-urban basin in Phoenix last July, our sensors hit peak flow 7 minutes after the first drop during an 18 mm in 20 minutes cell — still my personal record. Anyone clocked faster in a built catchment, and was it driven by continuous slot drains, tight curb inlet spacing, or just zero storage? I’m hunting resilient tweaks that knock the peak without killing conveyance.
We’ve seen 6 min in a 1.9 km² CBD during a 15 mm/10 min burst — continuous slot drains and sealed lids made it jump like it was on espresso. To knock the peak, try 20–30 mm curb weirs/orifice plates on every other inlet to force shallow gutter storage (adds about 2–3 min without flooding), but mind ADA crossings; what’s your “tight curb inlet spacing” and typical gutter slope?
And @OP, try orifice plate throttles at trunk junctions; even 5–10% delay tames ‘7 minutes’. Watch downstream HGL though.