Mayor Ron McRae and members of Council had a meeting with residents of the Morrison Subdivision last week. The Mayor said it was a good meeting.
“It’s looking like we have a pretty strong group of people who want to be part of a committee to look at strategies to mitigate flooding,” he said.
The City will also be implementing a flood bylaw with specific construction requirements for any new building in the subdivision.
However, right now there are 31 dwellings in the Morrison Sub, and residents have been through several floods, including the major flood last April.
City Council received two reports on the Morrison Sub area at their regular meeting on Tuesday evening.
One report was from Aqua-Tex Scientific Consulting and one from LaCas Consulting.
The reports give a good picture of the issues in the subdivision, and what steps might be taken to mitigate flooding.
Last spring, Kimberley Creek peaked at 2.78 meters over sensor depth on April 25. In the normal freshet later in June, the creek peaked at .879 meters.
The Aqua-Tex report simply states that left to its natural state, the Morrison Sub would revert to a wetland and Kimberley Creek would likely spread to multiple channels across the valley floor.
However, with homes being built on the valley floor, the creek was channelized; which is only partially effective and only during dry weather. An additional issue in Morrison Sub is a high water table. There is no practical way to drain soils because the bottom of the creek bed is close to the water table for most of the year. The channel of the creek can’t be deepened as this would only increase standing water, which would then have to be pumped up to the elevation of the culvert under the city.
An expensive solution would be to dig the culvert under the city out and make it deeper, but that is not something the city can afford, and the discharge from the culvert would have to be moved much further downstream for it to be practical.
The LaCas report also notes the channelization of the creek, and in addition the presence of numerous driveway culverts and footbridges.
“There are no existing properly designed flood mitigation works in the subdivision therefore during flood events it is understood that the existing main channel typically overflows its banks and spreads out across the relatively flat floodplain, inundating land, houses and outbuildings. The existing high water table at the valley bottom would tend to exacerbate the situation with the lack of significant ground infiltration during flooding.”
A number of recommendations have come out of the reports.
• The Kimberley Creek channel through the Morrison Sub should be widened and the banks reshaped to reduce scouring and allow vegetation to be established.
• All driveway culverts should be at least 1.2 meters in diameter.
• Where possible, the channel should be reshaped to a natural meandering pattern.
• Banks should be replanted with native shrubs and grasses to protect them during high flow events.
• Coronation Park was historically a wetland. With the water table quite close to the surface, it will not be able to contain flood runoff. It may be possible to create wetland habitat and improve flood storage by both excavating and berming a portion of the park.
There are other suggestions, which would likely prove cost prohibitive, such as the City gradually acquiring the homes in Morrison Sub.
It is also recommended that any municipal water and sewer lines should be set back at least 15 meters from the creek and residents should regularly inspect their culverts and remove any debris.
The Meadowbrook Waterworks dam above the Morrison Sub could also be increased in capacity to function as a flood storage dam.
The reports also made considerable recommendations that could be fit into the upcoming flood bylaw for the Morrison Sub.
McRae said that he sees the meeting with residents as a positive step but cautions that there is no ‘big fix’ in the immediate future.
“I see this as incremental, a beginning of incremental steps in water management,” he said.