The Village of Canal Flats passed the first two readings of an amendment to the Official Community Plan at the last Council meeting Tuesday, November 12th.
Aside from some wording changes and clarifying points, as well as a floodplain map, the amended bylaw states that the Village recognizes “that most of Canal Flats, including the area within the urban Containment Boundary, is located on an alluvial fan.”
Why does this matter? Alluvial fans are landforms filled with gravel, sand and smaller sediment like silt, created as water comes down from higher features like mountains or hills. The rushing water carries deposits to a flat plain. Alluvial fans are created when this sediment is deposited as the stream fans out on the flat ground. The B.C. government’s floodplain maps for the region note that on the Canal Flats’ alluvial fan (which was created in pre-history) “flooding depth(is) indeterminate in this area. In addition to possible inundation by over-bank flows, the entire fan area is subject to special flood hazard due to possible channel avulsion.”
Avulsion basically means that a river can break out of its channel for a variety of reasons, such as extreme runoff events. If that were to happen, there is a possibility Canal Flats could see some flooding. However, Adrian Bergles, Canal Flats’ CAO, said the risk of flooding is actually “quite low.”
To find out just what kind of risks there might be, the Village of Canal Flats is doing a study of flood risks for the Kootenay River to update almost 30-year-old information, thanks to a $150,000 grant from Emergency Management BC announced in May 2019.
“Being prepared is about understanding hazards and finding ways to better protect the public,” said Jennifer Rice, Parliamentary Secretary for Emergency Preparedness. “This funding will help local governments assess the risks that are unique to their communities and take steps to prevent and prepare for disasters.”
The last major floodplain mapping program for the Kootenay River at Canal Flats and Columbia Lake was released in October 1990. That report states: “The Kootenay River can experience quick changes in river discharge.”
Luckily, the Kootenay River does not appear to have ever flooded into Canal Flats. The 1990 report included interview results from several longtime Canal Flats residents. George Cockshott, who had lived in Canal Flats since 1931, said he was unaware of the Kootenay River ever inundating Canal Flats. There had, however, been flooding recorded both upstream and downstream of the community. In May 1986, there was record flow on the Kootenay River, with two nearby ranches reporting extensive flooding.
The report goes on to say: “The extent of the floodplain is defined by the valley slopes upstream and downstream of Canal Flats. At Canal Flats, however, the alluvial fan, being of deposited material, is not a permanent boundary of the river. The fan slopes from the river bank to Columbia Lake with an elevation difference of up to 10 m. At high stages, the Kootenay River could overtop the river bank and flow over land to the lake, or the Kootenay River could switch channels by eroding through the fan at the sharp river bend upstream of the bridge. Although there is no record of over-land flow from the river to the lake, an extreme event such as the 200-year flood could cause over-land flow or a major avulsion.”
The Village of Canal Flats is hosting an open house on Monday, November 25th to share more details about the Kootenay River flood risk assessment study, which Urban Systems is aiming to have completed by spring 2020. Staff and contracted engineers will be on hand to discuss community flood risk, steps taken to protect the community, and answer any questions residents may have. The open house takes place from 3:30-5:30 p.m. at the Canal Flats Village office.
The OCP bylaw amendment will go to a public hearing prior to third reading and adoption. The public hearing is scheduled for Monday, December 9th at 6:30 p.m. at the Village office.