Significant work continues in local steams and creeks to prepare for the spring snowpack melt. Freshet is the snow melt that typically occurs from April to July, in British Columbia. Freshet can become a problem when winter snow packs melt rapidly, overwhelming stream channels and creating floods.
As spring freshet approaches we closely monitor all flooding factors in consultation with provincial departments; including snow pack levels, temperatures and precipitation forecasts. Freshet flows depend on these factors and dictates the timing of peak flows. Preventative measures, such as sandbags or bladder dams, may be proactively placed along strategic locations throughout the city to protect critical infrastructure.
The potential for flooding exists every year, and property owners living near creeks, streams, low-lying areas and lakefront are responsible for having a plan and protecting their properties. Subscribe to receive email updates or learn more about local, provincial and federal preparedness resources at www.cordemergency.ca.
In 2017 and 2018, record setting rainfall in 2017 combined with snow melt, saturated ground, and high groundwater levels resulted in major flooding in Mill Creek with considerable damage to Bellevue Creek and the Okanagan Lake foreshore.
City staff and contractors are working through a list of 52 locations in Kelowna that require repairs after last spring’s snowpack melt and ensuing flood, at a cost of approximately $10.7 million. About $3 million in works completed or underway so far include the repairs to Upper Vernon Creek and Bellevue Creek dredging.
Creek channel capacity restoration projects continue to be our priority right now, with crews doing erosion remediation and more gravel removal from Bellevue Creek and Mill Creek. Contractors are also removing vegetation in and around Mill Creek, along with dredging to increase the creek’s ability to handle higher water flows that occur during spring runoff.
Bellevue Creek originates near Little White Mountain and flows northwest through Okanagan Park which also includes Crawford Falls and Canyon Falls before it reaches the apex of the fan near Woodhaven Regional Park and flows to Okanagan Park near Fuller Road. The lower reach of the creek is considered by the province to be Rainbow Trout and Kokanee fish habitat although it is not used extensively at this time. The reach from Woodhaven Regional Park to the mouth at Okanagan Lake has old berms along the tops of the banks in some areas that are legacy items from historical channel clearing by the province and some retaining walls near the lake on private property that were built to contain high flows.
The 2017 flood caused significant channel bank erosion and channel scour within the eastern region of the channel which resulted in deposition in the reach at the mouth of the creek at Okanagan Lake.
Pending Ministry approval, the City intends to repair the erosion and channel scour locations as well as remove the accumulated gravels within approximately 500 metres of Okanagan Lake. The City will also repair the trail berm and other damages in Cascia Drive Park.
Mill Creek originates in the hills northeast of the city and flows southwest through the city entering Okanagan Lake near the W.R. Bennett Bridge. After the creek crosses under Harvey Avenue near Burtch Road, it is constricted by urban development all the way to Okanagan Lake. These restrictions to the creek channel are an ongoing concern to the City and the Province since there is limited capacity to safely pass high flows during flood events.
In response to these concerns, the City and the Province constructed the Mill Creek diversion structure in the 1980s that can divert high flows for lower Mill Creek.
Since the diversion works were completed in the 1980s the channel downstream of the diversion has become progressively obstructed by vegetation. Some is brush that has grown into the channel, and some is large deciduous trees (e.g., willows) that have also grown in the channel and across the channel. All this overgrown vegetation has progressively restricted the flow such that in 2017 the channel was not capable of diverting the flow levels it was designed for and certainly cannot pass the bankfull flow recommended in the Ministry of Environment report. As a result of the obstructed flows, there was severe and costly flooding within the city during the 2017 high flows.
Damage to city infrastructure due to the 2017 flood was identified at Spencer Road, where it crosses Mill Creek. The flood damaged the three corrugated metal culverts and caused aggradation within the channel upstream of the crossingand resulted in overbank flows which caused extensive residential flooding.
Pending Ministry approval for the work, the City plans to repair the damaged culverts and remove accumulated gravels prior to the 2018 freshet. A longer range plan is to replace the existing culverts with a larger open bottom arch culvert (or equivalent). This project is in the planning and design phase. Pending funding and Ministry approval the works could be constructed in 2019.
The City's assessment also determined that the creek channel from Okanagan Lake upstream to Ethel Street has diminished capacity due to sedimentation. It is likely that this sedimentation is related to the flood event in May 2017. Vegetation, trees, and brush have encroached into the channel reducing the flow capacity to near zero in some locations. In addition, there are constructed obstructions (e.g., private fences) that collect debris and reduce flow capacity which contributes to the potential for flooding.
Pending Ministry approval for the work, the City will begin removing the accumulated sediment and offending trees and vegetation in the channel to restore channel bankfull design capacity. Due to the restricted access and complexity of the work involved, this project may take upwards of two years to complete the approximately 14 kilometres of channel.
Priest Creek Linear Park consists of a walking path and three wooden bridges to allow for pedestrians, cyclists, and equestrians access into the Myra Bellevue Provincial Park. This park provides a unique riparian experience as the walking path meandered alongside and over the creek. At the south end of the park, Priest Creek is confined by a steep valley that was burned during the 2003 Okanagan Mountain Park fire. The northern portion of the park is undisturbed natural forest and the valley floor expands onto a fan; historic channels are evident. The walking path was surfaced with crushed gravel on the fan and left as a natural dirt path at the south end of the park where the path climbs away from the creek on the east side of the channel. Currently the park remains closed as it is not safe for public use.
The 2017 flood caused significant channel erosion and scour as well as several channel avulsions within the park that isolated two walking bridges and damaging the walking path in several locations.
Due to an upstream channel avulsion, the creek formed a new channel west of the original channel which was diverted by a deflection berm back into the main stem near the north end of the park. The walking path crosses the new channel after passing over the deflection berm.
At two of the bridges, bed material filled in the original channel causing channel avulsions. The new channel has scoured to a greater depth than the original channel making it both difficult and expensive to try to restore the flow to the original channel. Since this is a small natural park area, it is recommended that the flow be maintained in the new channel and the path be extended to cross the new channel using fords rather than bridges.
As a result of the extent of disturbance in the channel through the park it is expected that the flows will remain high in the future during spring freshets. For this reason, ford crossings are recommended rather than installing new bridges since a ford can be easily restored after a spring freshet if necessary. If fords are used it may be necessary to close the park during the spring freshet when it would be unsafe to cross the flowing stream. This approach is commonly used elsewhere where walking paths may be flooded during high flows.
Pending Ministry approval, the City plans to restore sections of the walking path by removing gravel and debris from the path, constructing stream ford crossings, and repairing one bridge.