Trap Lows

Water accumulation on your street may be because of a trap low


Some homes in Town are located near a trap low, a device that controls water drainage from Town streets. For homes near trap lows, rainwater may accumulate on the road nearby, up to and sometimes including the driveway and a portion of the lawn. This is normal for areas with a trap low. The water should completely drain within 24 hours once the rain stops.

If water has accumulated on the road near your house, on your driveway or front lawn, you may be located near a trap low. If rainwater accumulation has not drained 24 hours after the rain stops, please contact Town of Cochrane Operations at 403-851-2590.

Example of the water pattern on street with a trap low. [link]

Information about the trap low may be on your property title.

What is a trap low?


Trap lows are used in many neighbourhoods in Cochrane to slow the flow of water into stormwater ponds. We control the flow into stormwater ponds to reduce erosion and allow sediment to settle before the water flows into the Bow River. Alberta Environment requires the Town to control the flow of stormwater into the river to protect the overall environment.

In streets with trap lows instead of traditional storm drains, it may appear that the street is flooding. It is not. Trap lows are designed to hold the water on the street; properties on streets with trap lows are graded to keep the water from foundations.

Go to Town maps to see trap lows:
1. Click the arrow beside Base Map to view the options.
2. Check the box beside Trap Lows to turn on the trap low layer. Trap lows are marked in purple.
3. Zoom in on any area using the zoom tool (magnifying glass with +) in the top right corner.

Why the Town has trap lows


The Town began requiring trap lows instead of traditional storm drains in neighbourhoods built after 1998.

Because trap lows control the rate of release into the storm water system, it is easier to ensure the pipes will not become pressurized from upstream flows and cause potential issues downstream. If the flows are not controlled, downstream impacts could cause manhole covers to lift off posing a serious safety concern. The storm pond would also discharge the stormwater into the waterways at a rate that could cause erosion.

Is any action required?


In general, no action is required by homeowners who live near trap lows. If rainwater accumulation is not drained 24 hours after the rain stops, please contact Town of Cochrane Operations at 403-851-2590.