I used to have a stand pipe but converted it to a 6" siphon. The siphon is just a gravity drain until about a 4 or 5" rain puts it into full siphon mode. The shut off air valve that runs back into the pond is below full pool, therefore the siphon mode stays on until the pond comes down to this level. The siphon is capable of pulling down below this valve even during major events or soon after.
I think the creek in question is a bit more than half of the inflow during peak events.
