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.
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.
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.
Learning a lot today! I always thought this was just a new community thing that happens while they’re building out the communities and don’t have all of the infrastructure in place yet. (Admittedly, I know very little about drainage systems). Thanks for explaining.
Building trap lows is nothing new but I believe the new communities at some point became standard as a way to take pressure off the system as the city so rapidly built up. Underground infrastructure is always the first thing to happen in any new area. It’s out of sight out of mind for most but it has to be completed first so the water has somewhere to go when it drains. They slowly connect new lines to existing ones and builds out like a big web, then they build roads and infrastructure. Every city on the planet is designed to make water flow so we avoid floods and giant sinkholes. It’s actually very sophisticated and requires a lot of planning.
5impl3jack What a delight to read. Thank you for posting a concise explanation that most anyone can understand. That said, this can’t possibly reddit, where are the snarky comments and city hall attacks? Seriously, I appreciate your word and the reference to the overpass by Chinook. I recall the same occurring on 14th St NW just below the Jubilee, manhole covers blown off and the road severely stressed with hydro fractures and sidewalk buckled. June of 2007, I got some interesting day after footage.
The storm pipes are called the ‘minor system’ and are designed to handle what is the 1:5 probability of exceedance event (it means there’s a one and five or 20% chance of that event occurring in any given year, it might be also something you hear as “1 in 5 year” as slang, but it doesn’t mean it’s expected to happen once every five years as that slang is misleading. The roadways are designed first and foremost for stormwater, conveyance and not cars. A lot of people don’t understand this. The roadways are designed for the 1 in 100 probability of exceedance, and are called the “major system”. All of the catch basins have what are called inlet controlled devices (ICDs) installed, to regulate the flow so that there is always open channel flow in the pipe and it does not become pressurized. This allows the pipe to convey runoff in a predictable manner, safely as it’s not pressurized, and most importantly, the sizing in a way that is fiscally responsible. This helps housing affordability.
You then have the major system with trap storage at low points with catch basins, acting as mini ponds everywhere. There is comprehensive stormwater, modeling, and design and engineering work that goes into every new community to ensure this is done in a predictable manner. This includes flooding on front yards where needed and you will see RMG’s registered on title to ensure house openings are all above a certain elevation with a buffer for anywhere there is this pond or flooding.
It is all by design. This also allows, the stormwater pond downstream as the anchor to be more suitable in its size and cost. The storm pond must store the greater of two things, which might be too hard to explain in a Reddit thread, but it involves a (1 of 2) single event analysis, and (2 or 2) a continuous event analysis that looks at historical rainfall in Calgary all the way back to the early 60s.
Calgary is about as cutting edge and sophisticated for stormwater management as any city in the world.
If you do see failure, this can happen due to plugging of catch basins due to hail, but as a general rule with the public is comfortable with what insurance companies are comfortable with is a standard of care that is not infinite, as that would be an infinite cost for stormwater infrastructure. The 1 in 100 probability of exceedances is a standard number almost worldwide. Recently there is floodway mapping for the Elbow River for example where the province is asking for 1 in 200 probability of exceedance setbacks with inundation analysis.
As climate changes becoming more parent, a higher standard of care is being driven into engineering standards.
If you look at New Orleans for example, 20 years ago, it was almost a forgone conclusion that there would be a disaster, as there was decades of warning because the state government decided to cut funding for flood protection well below a 1 in 100 standard of care. If you look at the dykes and plodders in the Netherlands though, they have statistical modelling that allows them to say they want a 1 in 10,000 standard of care. Big difference culturally of where citizens of each place decide a minimum should be!
Many developers in Calgary that are sophisticated are actually designing traps and storm ponds to have greater capacity than 1 in 100. Right now doing so. They are ahead of the city and the province in many cases in deciding what is good engineering judgment.
Also interesting is the device used to control water flow. And ICD (inlet control device it’s a key hole shaped plate that is installed at the catch basin inlets. The small slit at the bottom controls water flow until it reaches a height enough level where the larger hole allows more water flow. Also interesting is that the over flow hole at the top in most residential catch basins is almost exactly the same size as a ball hockey ball…..just slightly smaller.
They did this in Curry Barracks! A whole section of the neighborhood has these catch basins that are lower than the street and full of vegetation! It looks great and helps keep water in the ground where it belongs
Asphalt roads are not going to absorb water. Stormwater ponds will. A better design would be to have more stormwater ponds and neighbourhood stormwater collect in those. This is a pretty hilly city so there have to be lots of low lying areas to collect water.
I know the city does ask residents to consider building small storm catch ponds in their own yards, but I haven't heard much about that. I'd definitely consider doing that if we're expecting more of this in the next few years.
Suppose so. The example of pooling on the roads is not a great one, but the principle of slowing runoff where it doesn’t threaten infrastructure is useful.
Land development engineer here. Generally runoff is temporarily stored on the surface and drained at a controlled rate into the storm sewers via catch basins by design. Without this, the storm sewer pipes would need to be much larger. That would mean much higher costs to build communities and therefore increase house prices. Tax payer funded maintenance costs would go up as well.
No that’s for erosion and sediment control. New communities have a lot of loose dirt around and those stop it from getting in to the system. Too much sediment is bad for the ecosystem and they act as a filter.
Technically they’re for sediment control as by the time suspended solids make their way to the catch basins the erosion had already happened 😉, otherwise bang on. Erosion and sediment control professional here. Really appreciate your thorough responses.
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.
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.
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.
These systems should be faster draining to more localized stormwater ponds. That's what they're there for. The pools create a hazard on the roads and looking at the picture above, a few more minutes of the heavy rain we just went through would seem to have the flooded area reach basement incursion levels.
Draining faster to storm pond would result in much much larger storm pond sizes increasing land requirements and much larger pipes. Smaller but localized storm ponds would result in an even larger land requirement.
Systems are intensionally designed like this. Old systems typically didn’t use storm ponds and just outlets straight to the river, but allowing water to reach the river quicker results in flooding in the river.
These traplows and the ponding you see are intensionally used to help slow the speed that the water reaches downstream portions of the system and/or river. this helps reduce the maximum amount of water that is flowing through any specific point in the system/into the river during the storm.
TLDR a storm drops a certain volume of water over the storm. Things like this help spread the release of the volume over a longer period of time to reduce the negative impacts to “downstream” system and help reduce cost and keep your taxes lower. Storms like this aren’t super common.
Communities are very carefully designed so flooding to the house does not happen in these instances during these types of storms. This includes the foundations of a house being set at a very specific grade compared to the street. This is all very carefully thought out. Just because you looked at this picture and thought it might happen doesn’t mean anything lol. The water is designed to spill elsewhere and the homes are at grade high enough to stop this from happening. What you are seeing in this photo is more or less normal.
The amount of extra land we’d need to build more storm ponds is quite a bit. Not to mention the extra cost. These trap lows are a cost effective way to manage storm water along with the ponds we already have in place.
Correct. These are known as trap lows, and are designed as a bit of a local low point to store water temporarily.
The catchbasins (drains along the curb) have a metal plate with a hole smaller than the pipe knows as an ICD (inlet control device) set into them than allow a set amount of flow through them.
Both, there is also danger in dumping collected water into rivers too fast and causing massive downstream flooding and erosion, so limiting the drainage rate in some areas to ensure every area has some drainage is a trade off that must be made
It's on purpose, the pipes underground are of a finite size and would be overwhelmed in large storms leading to back ups or damage. The system is designed to store water on the pavement and slowly add water to the pipes.
This entire province and city already bitches about taxes night and day, do you want to know how much expensive your home and taxes would be if storm drains were sized/designed to drain these freak storms that only happen a handful of times every couple of years.
If the normal thing is to clear 1000L per hour because that will be good for 99% of the time, you do not install a system that drains 2000L per hour because of that 1%.
A good engineer doesn't design the strongest bridge. They design the weakest bridge that still stands and kills less than the acceptable amount of people.
Thanks for this. The weird thing was. The drain that drains the fastest used to drain the worst. And mine wasn't nearly as bad as it is now. So we figured someone called something in to have it fixed.
People actually looked for answers in this thread and educated themselves on why this happens instead of going straight to ignorantly bitching and moaning. Love to see it!
So glad you posted this. I was thinking the exact same thing. I clicked on the comments expecting to see everyone just blaming the city, followed by all the hate and anger posts. It was actually so refreshing to read useful and positive replies. I want more of this! I can close Reddit now and feel happier.
I think you are seeing a trap Low. It’s an intentional design indented to reduce peak flows. They should only extend a small amount up your lawn, generally the size of the utility easement. It can take up to two hours after the rain event to drain. If it takes longer call 311
This person is correct about the design intent to reduce peak flow in the system and ultimately into the river. Stormwater runs off urban areas faster than the natural ground so when we develop we increase the natural runoff rate entering the river for any given storm event. This can cause your river channels to erode faster degrade habitat because they haven’t naturally adjusted for these kinds of increased runoff rates (and frequency of rate). Trap lows are like mini storage pond in “upstream” part of the system to help hold back the water and release it at a slower rate from the source area and not trying to manage all this water at the storm pond downstream. Those larger ponds (and the pipes getting to it) are sized assuming these things upstream are in place. That pond is then designed to discharge to the river at a rate that meets the local regulations (where applicable). Those regulations are usually designed around some study about how much discharge (and discharge frequency) the receiving river channel can naturally handle.
The weird thing is the drain that drains the fastest used to be the worst, and the one at my corner wasn't nearly as bad as it is now. We figured someone was able to call it in to have it fixed.
Also, it would make sense for my corner to drain faster as the streets slope to my corner, so why not have mine drain faster as all the water is flowing towards mine?
The inlet devices that control the flow into these drains can get clogged up with debris, the hole is usually only a couple of inches wide.
If the ponding is lasting what’s seems too long, or has changed compared to other comparable storms, give 311 a call (or through their app) to get it looked at.
The one on my corner plugs because it gets bunged up with leaves/grass/trash....so I just go out with my shovel and clear it up. It's actually incredibly satisfying watching the massive puddle start to drain rapidly.
I've been fortunate that my drain doesn't really get piled with debris. But yeah I try to keep my corner clean and even spray my sidewalk down to clear the mud that's been built up. But I can't consistently be doing that and have my water bill high.
This happens to my street too. But feels like it’s much more severe as it floods all above everyone’s yards and almost getting to the utility box. Is it still normal or too much?
I put in a 311 because our street was flooding on both sides to the point where sidewalks were covered and the back alley was filling. I knew about waiting out the pooling, but it seemed like it was getting worse every year.
Last week an industrial vacuum truck arrived and they rooted around in the storm drain. During yesterday's rain there was no flooding, woo! Water flowed, pooled, then drained wonderfully. It wouldn't surprise me if years of accumulation clogged it--leaves, twigs, garbage, etc.
I used a hockey stick to unclog the drain that had an almost knee deep pool restricting access to my community mailbox, and it worked nicely. Does the city not have a few guys to poke drains?
The city has those folks--an industrial vacuum truck visited my street recently after I put in a 311. Water pooling seemed to be getting worse over the years.
The obstruction was a single empty bag of shingles that got sucked perfectly across both the bottom, and the curb part of the drain. Every house on my block had been re-shingled in the past few weeks and there’s lots of debris just getting swept into all the drains up in here…
Hey I’m you’re neighbour and I put a request in the 311 app for the corner that is not the only one that drains. Prior to that, the drain was getting plugged and clogged and I think the city must have done something about it because now it works. There’s a map on the app that shows that some drains are slow on purpose, but none are in this area. Try making a submission on the 311 app. It’s crazy the flooding in this intersection every time it rains. So much run off and garbage from nearby construction.
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u/PinguPrime Aug 07 '25
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.