Wilket Creek Rehabilitation Project
THE WILKET CREEK SUBWATERSHED OF THE DON RIVER
Wilket Creek is a second order tributary to the West Don River, it has a drainage area of 15.5 km2. The northern portion of the channel south to York Mills Road is a series of piped systems. South of York Mills Road the creek is an open channel for approximately 4.5 km, ending at its confluence with the West Don River.
About 80% of the Don River watershed is urbanized and 100% of the Wilket Creek subwatershed is urbanized. The southern portion of Wilket Creek is one of the few remaining open channel tributaries in the Don River catchment area. Of the remaining open flow tributaries Wilket Creek, Taylor Massey Creek and Burke Brook have sustained the longest and most dramatic hydrological change due to urbanization in all of Southern Ontario.
Wilket Creek historic aerial shot, 1954. (Source: TRCA, 1954)
CREEKS UNDER STRESS
Rural watersheds have permeable ground and natural cover which facilitates a slow response to rain events. This is because most of the water is absorbed by soils, intercepted by plants and runoff is collected and stored in low lying areas until it evaporates or percolates into the ground. On the contrary, because of the impervious nature of development, urban watersheds experience sheet flow directly into storm drains. The smooth surface of storm pipes increases the flow velocity before it outlets into an open channel, catchment pond or the lake.
Wilket Creek has no major tributaries, it receives water from local drainage, storm sewers and some ground water. The buried catchment area north of York Mills Road to Steeles is older and densely urbanized with few to no stormwater management controls. As such, flows in the creek rise and fall rapidly following precipitation. This "flashy" nature of the watercourse results in a destabilized system with rapid and/or precarious adjustments in size and shape in order to accomodate for the increased flows.
Destabilizing adjustments result in:
- Increased cross sectional area of the channel
- Downcutting into the channel bed
- Increased sediment loads due to the erosion
- Changes to typical channel characteristics such as meandering patterns
- Decreased quality and quantity of habitat
- Degraded water quality
- Loss of riparian vegetation
Unfortunately, Wilket Creek has experienced all of the above types of watercourse degradation.
EROSION IN WILKET CREEK
Because of its rapid degradation a number of erosion control measures have been implemented in Wilket Creek over the years. Primarily, the use of old fashioned, conventional engineering controls like hardened (concrete) beds and banks, rip rap, gabion baskets and armour stone have been used. These structures have often resulted in complete failure or promoted increased erosion adjacent to or near the structure. Additionally, the ecologic integrity of the system has suffered, almost eliminating aquatic and riparian habitat in eroded areas.
In the late 1950's the North York sanitary trunk sewer system was built within the Wilket Creek valley bottom, crossing under the watercourse in several locations along its length. Where the watercourse and sanitary lines intersect, the pipe was encased in concrete. Currently there are multiple sites where the encasement is exposed, one site where the concrete has been eroded down exposing the pipe, and a few locations where the pipe is exposed due to migration of the watercourse. Many of these sites have since been repaired and protected.
Exposed pipe and concrete encasement in wilket creek. (Source: TRCA, 2012)
Other erosion hazards exist including degraded public walking paths, under-sized and degraded pedestrian bridges, outflanked manhole chimneys and increased riparian-tree hazards. Mitigating these hazards and preventing future hazards and further ecological degradation are the primary reasons for the ongoing work within the Park.
Ministry of Environment, Ontario (MOE). 2003.Ontario Ministry of Environment Stormwater Management Planning and Design Manual.
THE PROJECT BACKGROUND
The Wilket Creek tributary of the West Don River was one of the watercourses that suffered a significant amount of damage as a result of the August 19, 2005 severe weather event as seen in the photo below. The City of Toronto subsequently retained TRCA in 2007 to manage, design and implement large-scale restoration works within Edwards Gardens and 10 repair projects focused on infrastructure protection and public safety in order to return the Wilket Creek Park system to a state of good repair.
Shortly following completion of the aforementioned restoration work, another severe storm event hit the Toronto area on June 23, 2008, damaging three of the sites recently repaired by TRCA. It was evident by this point that a comprehensive study and rehabilitation plan was required to provide long-term protection for municipal infrastructure and public safety within Wilket Creek Park.
Post 2005 storm damage. (Source: TRCA, 2005)
In 2009, Toronto Parks, Forestry & Recreation (PF&R) and Toronto Water identified multi-year funding commencing in 2010 for the "Wilket Creek Channel within Wilket Creek Park Rehabilitation Study and Geomorphic Systems and Habitat Study" requesting TRCA's assistance to manage the Project on their behalf, including the implementation of any works recommended. The study was completed as a Master Plan under the Municipal Class Environmental Assessment process. See the Geomorphic Master Plan link to download a copy or view a summary of the report.
Following an initial assessment by Parish Geomorphic, the consulting firm retained by TRCA to assist with the study and design components of the project, three areas within Wilket Creek Park were identified as requiring immediate attention due to the risk to municipal infrastructure and/or public safety. These sites are referred to as Site 3, Site 6 and Site 7 by TRCA and the City of Toronto. See the map below which illustrates the reaches and project sites along Wilket Creek.
Given the anticipated length of time required to complete the study phase, the repair of Sites 3, 6 and 7 were recommended to be expedited for repair as emergency works, with the understanding that the designs for these sites will be in alignment with the overall strategy for Wilket Creek within Wilket Creek Park Rehabilitation Master Plan. Because of the scale of the proposed work, the emergency works were broken up into a number of steps to be undertaken within a short term, 5 year plan. The phases of emergency works are outlined as follows:
Click on each phase below to view more information and project updates.
Phase I Emergency works:
Protection of exposed sanitary trunk sewer crossings and bank stabilization at sites 6 & 7 (completed May 2011) No web page at this time.
Phase II Emergency works:
Site 6 & 7 trail and channel reconfiguration included a new 30 m bridge and concrete board walk, habitat enhancement and watercourse restoration. (Completed May 2012) No web page at this time.
Phase I & II before & after representative photos. (Source:TRCA, 2008 & 2012)
Site 3 Phase 1 (North) channel re-alignment to bring the watercourse away from valley wall contact, installation of new 30 m pedestrian bridge and restoration work. (Completed May 2013)
Phase III before & after representative photos. (Source: TRCA, 2008 & 2013)
Site 3 Phase 2 (south) & Site 2 channel re-alignment to bring the watercourse away from sanitary infrastructure and protection of the sewers by concrete encasements and armourstone retaining walls, channel widening, habitat enhancement, trail re-alignment and bank protection works. (in progress, to be completed fall of 2015)
Phase IV before, representative photo. (Source: TRCA, 2014)