With all the rain the last couple of days, our eyes turn to river monitoring. The City has issued a high stream flow advisory for the Elbow, so anyone near the water should be aware of the risks of higher than normal water level and flow.

However NOTHING IS ALARMING and this is well within the City’s ability to fully manage. We did think a quick post was appropriate as it is an interesting rain event.

On the Elbow River, conditions at noon were:

• Flow downstream of Glenmore:                      80 cms
• Flow into Glenmore  at Sarcee Bridge            80 cms
• Flow at Bragg Creek:                                       38 cms

 The Elbow River risks overland flooding at 150 cms.

On the Bow River, conditions were:

• Flow near Cochrane:                                       300 cms
• Flow at Downtown Calgary:                            268 cms

The Bow River risks overland flooding at 850 cms.

Please refer to the City’s resource on understanding flow rates.

It appeared to us that the storm we’ve had was centered more on this side of the mountains and, regarding the Elbow River, we thought of the location of the Springbank Off-Stream Reservoir (SR1) project relative to the McLean Creek (MC1) project that would be located further to the west and higher in the watershed.

We asked the City what it was tracking in this system and they provided the following intel:

• Rain on Thursday, May 21 (averaging about 45 mm) occurred primarily between Forget Me Not Mountain and the City, i.e. the lower, eastern part of the watershed basin.
• More than half of the peak flow was generated below where MC1 was located.
• This is similar to how the 2005 flood evolved.

SR1’s proximity to Calgary

This ‘blocking pattern’ event restricts the eastward progress of major low-pressure systems, thereby trapping incoming Pacific and Gulf of Mexico atmospheric moisture into the east slopes, thus making the front ranges and foothills likely to receive high precipitation amounts.

This is a fairly common occurrence and what drove the 2013 floods, which of course had a much higher rainfall density on already saturated earth.

This pattern is one of the reasons the City supports SR1 over MC1.

One of the benefits of SR1 over MC1 is the closer proximity to Calgary meaning it is better able to capture rain in the Elbow watershed no matter where upstream of the City it falls. Similar to an eavestrough on a roof – placing the trough at the top of the roof would not be as effective as at the bottom.

So no reason to be alarmed right now, as we all tend to be on edge this time of year. And on the Elbow River, the new Glenmore Gates will provide additional Glenmore Reservoir water storage capacity, which is of course helpful to protect downstream businesses and residences to a greater degree.

If you’d like to get in touch, please reach out to info@crcactiongroup.com.

Regards,

Your CRCAG Board