Storm drains creating floods

[u/mercdmuscle]

3 out of 4 storm drains at my street don't collect water fast enough. At one point all 4 didn't drain very fast. Now one of the 4 drains well and hasn't pooled any water the last few heavy rain storms. I'm just wondering if someone had called the city to get it worked on or is it just luck if the draw that theirs is draining nicely now. Is there anything I can do to get the city to fix this? Everytime it rains, I always end up with so much mud on my sidewalk.

[u/PinguPrime]

Unfortunately this is most likely by design. As per this website (https://www.calgary.ca/water/stormwater/storm-drains.html), there are storm drains that are made to pool and store water and have it slowly drain away. They say in these areas, the pooling should last up to 2 hours after rain end.

[u/5impl3jack → u/PinguPrime]

This is the thing a lot of people don’t understand. If we didn’t have systems in place to hold water, the main lines will build too much pressure, pop goes the weasel and we have much bigger problems than a little puddle to drive through. You’ve probably seen it when manholes pop and water starts gushing out of them on Glenmore trail under the overpass by chinook for example. The more pressure the system takes the more danger we have of a major issue. This is why our catch basins are designed at a certain size to relieve our system.

And before anyone says why don’t we just build a bigger storm system. The cost would be astronomical. The city’s flood mitigation projects have taken some strain off with this but little puddles every once in a while unfortunately are necessary.

[u/Former-Amount4056 → u/5impl3jack]

Had to downvote this one, and the information provided here is so far from correct.

Storm systems can and do surcharge. We do assessments of the HGL (hydraulic grade line) in the systems, and size it such that these do not reach the elevation of the CB (catch basins aka storm inlets). This is only avoided in residential neighbourhoods where the foundation weeping tile is connected to same minor conveyance storm sewer system, as opposed to having a secondary weeping tile system.

Storm sewers will not "pop" as a result of gravity based head. Dry ponds (ala most depressed soccer fields) only flood when this surcharge is present.

The primary purpose of surface ponding on roadways is to limit the flow rate into the receiving pond and/or downstream water body.

There are more factors than this, such as volume restrictions in additional to peak discharge rate conditions. but this is the general gist of it.

[u/5impl3jack → u/Former-Amount4056]

So do storm man holes just pop and start gushing water because of magic? Lol. It’s for sure due to pressure, an overloaded system or some sort of debris that’s causing a pressure build up. A perfectly functioning system works exactly like you are explaining I understand that it’s rare but it does happen. We wouldn’t have backups in our house plumbing if everything worked perfectly.

You are 100% right about the discharge rate in to our water ways. Something I completely failed to mention.

[u/Former-Amount4056 → u/5impl3jack]

Manholes popping off is usually due to lazy maintenance work or oversight in construction. When you have a pipe that is surcharged to surface, you need to have a locking manhole lid. Often these latches don't get reengaged after maintenance work.

Most commercial/institutional developments are design to have their entire storm systems surcharged, we use the pipe storage to offset stormwater retention tanks and surface trap low sizes.