# Computing the velocity of water under reverse flow conditions from storm water drain

I am trying to compute the approximate velocity of water during reverse flow from the outfall location to the street through storm inlets. This is generally seen during what is commonly referred to as the sunny day flooding. The figure below illustrates the scenario - I am trying to compute velocities V1, V2 and V3.

Water enters the drain pipe because of high water head in the sea, and it then moves along the storm pipe and discharges on the streets via storm inlets. I want to compute the approximate velocity of water that is getting discharged on the street for modelling purpose. The head of water in the ocean, elevation of street and storm inlets, pipe diameter, as well as the elevation of the bottom of the pipe is know. Appreciate any pointers you can provide. I was thinking some form of principle of conservation of energy needs to be applied, but not sure.

• Apply V=IR from circuitry land. Voltage is like pressure. Current is like flow rate. Resistance is some number, but can be roughly approximated as proportional to length and inversely proportional to area. Baseline the model against measurements of water levels over time. Then apply the model to data that was not incorporated into the model itself to tell how good it is.
– Abel
Commented Nov 8, 2023 at 12:09
• Thanks Abel. I like the idea of using length as a proxy for resistance. Commented Nov 10, 2023 at 1:42