The MRG sent a letter to the City of Toronto on April 3, 2025, to provide comments on the Yellow Creek Geomorphic Systems Master Plan.
The Midtown Ravines Group appreciates the opportunity to comment on the Yellow Creek Geomorphic Systems Master Plan (GSMP), issued on 5 March 2025.
The Midtown Ravines Group (MRG) is a consortium of ten residents’ associations in midtown Toronto that is advocating for a comprehensive plan to restore the Vale of Avoca (Yellow Creek) ravine. The MRG is currently engaged with members of City Council and staff from various divisions on specific proposals for the comprehensive restoration of the Vale of Avoca, including erosion remediation, renewal of municipal infrastructure (such as storm sewer outflows), rebuilding the ravine trail system, and restoration of ravine ecology (including the control of invasive plant species).
The MRG believes that the release of the 2025 Yellow Creek GSMP represents an important element of progress towards the restoration of the Vale of Avoca. This particularly relates to the provision of a wealth of information and analysis on the factors that have contributed to the degradation of the stream channel over recent decades, and consequently to the ongoing deterioration of ravine slopes and of the park trail and access infrastructure. We expect this information will enable detailed design work that will lead to permanent solutions to the problems underlying the ravine’s degraded condition.
We also believe that the report provides important context for evaluating approaches to ravine remediation. This particularly relates to the characteristics of the watershed and of the ravine itself, and to expectations for continuing intensification of extreme weather events that are a primary source of stress on the Yellow Creek geomorphology.
We would like to highlight the limitations of the GSMP report itself as a road-map for the work needed to bring about the remediation of the Vale of Avoca. The GSMP is explicitly labeled as a “Master Plan,” but we believe it is important to recognize that it takes an extremely narrow view of the problems that it addresses. For a more complete listing of the issues in the ravine, see the attached ‘Community Vision’ plan for the Vale of Avoca, also circulated to our councillors and to City staff.
According to the GSMP itself, the “Master Plan outlines an integrated plan guiding subsequent infrastructure projects or municipal works based on a holistic view of the area,” (page iv). However, in our view, the content of this study falls well short of what a master plan for the ravine should encompass, since the study restricts its primary focus to the evolving condition of the ten locations for Toronto Water infrastructure that are at- risk due to degradation of the Yellow Creek watercourse and its banks. This focus determines the scope of remediation considered, the prioritization, and the recommended sequencing. As a result, within the next 10 years, the recommendation would only address a total of 85m of the Yellow Creek stream course, in proximity to one sewer outlet judged to be most at-risk, relative to the 1.3km total length of aboveground creek bed. This is anything but the holistic approach to ravine restoration that is required to reflect the community interests in the ravine.
The prioritization fails to consider the degraded condition of the ravine trails and access points, and the dynamic nature of erosion occurring at many points along the ravine, as well as on the ravine slope itself. Furthermore, the proposed sequencing of the four defined project components fails to consider the destructive impact of construction staging and access to adjacent sections of the ravine.
The study suggests that the staging of construction work will use the Avoca Ave access for project components #1 and #3, but will use the Mt Pleasant Rd access for components #2 and #4. Despite this, the recommended sequencing of the projects (#1 through #4 in serial order) implies that construction staging and access will alternate at each new stage between the Avoca and the Mt Pleasant access areas. This suggests that habitats and park amenities may well be subject to continuous disruption over a 20-year period. Furthermore, it seems to imply that, for a given project location and access route, a successive period of active disruption will reoccur perhaps five-years later, imposing further destruction on any regeneration that had occurred in the meantime. This is not only wasteful but designed to maximize disruption for the many users of the ravine.
In addition, the fact that the plan 2025/26 remediation project below Heath Crescent will likely use access via Avoca Ave, is not taken into consideration as a reason to address project #3 in conjunction with the Heath Cresent project. Again, wasteful and disruptive.
Given the relatively low priority assigned to all but one of the sewer outfalls, the GSMP raises the strong likelihood that the three most troubling areas of erosion may only be addressed late in the 20-year outlook period (indeed, if at all). These three areas of erosion include (1) the western ravine bank near the closed St Clair bridge access route;
(2) the continuing streambank collapse at the sawmill site below Inglewood; and (3) the growing sinkholes beside the remaining pedestrian bridge across Yellow Creek. Failure to address these priority issues is dangerous as well as myopic.
In light of the foregoing, we strongly encourage close collaboration of the relevant City divisions to work with Council members and community stakeholders to develop a more holistic plan for the Vale of Avoca that takes advantage of the thorough research and analytics compiled as part of the work on the Yellow Creek GSMP.
Attached to the letter were detailed comments.
MRG detailed comments on Geomorphic study MRG Community Vision for Vale of Avoca ravine
While the report’s recommendations focus on priorities concerning Toronto Water infrastructure, its data collection and analysis make it an invaluable resource for the development of a Master Plan that implements the vision set out in the Midtown Ravine Group’s Community Vision for the Vale of Avoca.
1. Relevance to overall Vision Plan
The key components of the MRG Community Vision are:
- A reconfigured and refurbished trail network that provides well-designed access points, loop trails, and through routes connecting with other elements of Toronto’s ravine network.
- Remediation and repair of the Yellow Creek stream channel and adjacent slopes, providing erosion control that can deal with the impact of anticipated climate change.
- Removal and improved control of invasive species in the ravine habitat.
The recommendations of the Geomorphic Study report focus on actions required to protect Toronto Water infrastructure in the ravine, and as such are largely limited to only one element of the second component listed above. The Master Plan required to implement the MRG Community Vision requires a more holistic approach that deals with the entire ravine, not just storm sewer outfalls, and integrates planning for erosion control with the other components of the Community Vision.
2. Major findings of the geomorphic study
The Geomorphic EA report’s most important contributions are its documentation of the ravine hydrology and specification of design standards for future erosion control projects.
Yellow Creek has to be viewed in two different potential states: Under normal conditions, it is a bucolic stream providing a significant element of the ravine experience for users of adjacent trails. During major storms, it is a raging open storm sewer with a dramatically increased flow.
As the report notes, the hydrology of the creek is markedly different from what it was when channelized with quarried rock walls back in the 1890s and early 1900s, both because of the increased frequency and severity of extreme weather events (climate change) and the paving- over of the watershed, which was still farmland a century ago (urbanization). The result of this altered hydrology is that the existing hardened Yellow Creek channel from the 1890s is inadequate to handle the extreme weather events of the 2020s. Indeed, the narrow and hardened channel configuration may in several sections (for example, at the pedestrian bridge)
have exacerbated some of the more pronounced areas of erosion. An updated design standard for potential channel remediation projects is required; the geomorphic study makes this clear.
The critical analysis is set out in sections 6.1 and 6.2 (pages 50-69) of the report, beginning with Tables 13 (Yellow Creek Design flows) and 15 (Critical Shear Stress).
Here, it is useful to compare the assumed flow rates specified in Table 13 with numbers for a recent storm event on 16 July 2024, in which a 100 mm rainfall was recorded for Toronto over a 3-hour duration (with a corresponding local measurement of 97 mm over the same duration).
Over the 10.25 km^2 of the Yellow Creek watershed, this amounts to a total volume of approximately 994,000 m^3 of water to be drained, roughly 6.3 times the assumed flow rate for a 100-year storm. In the past twenty years, Toronto has seen at least four storm events (August 2005, July 2013, August 2018, and July 2024) that have exceeded the assumed 100-year storm. While we do not wish to belabour the point, we question whether the assumed flow rates for storm events adequately incorporate the effects of accelerating climate change.
The report’s conclusions for future stream remediation projects reflect this uncertainty by recommending (Appendix K9 and elsewhere) a combination of large-boulder-slopes and armourstone walls, along with potential widening of the streambed. Implementation of the Community Vision proposals should reflect the Study’s conclusion, erring on the side of planning for substantial storm flows.
As the report emphasizes (pp. 50-69), lack of upstream surface permeability resulting from urbanization causes stormwater flows in the ravine to be characterized by a rapid response to rainfall, which together with the streambed slope results in high stream power. Apart from hardening of channel walls, the primary tool for reducing stream power and so lengthening the life of erosion control investments is to increase the width of the streambed. We assume this as a design goal in implementing the Study report’s recommendations.
3. Consistency of channel remediation proposals with proposed path network
We discuss proposals by Reach #, with reference to the large-scale maps of existing conditions (see Figures 4-7 appended to the Geomorphic Study report and Appendix K). Of prime concern is that path repairs and construction be integrated with remediation and repair of failed stream walls in order to minimize disruption resulting from construction.
Reach 1 (Report Figure 4, Appendix K-1) Cemetery to St. Clair Avenue road bridge
The proposed main north-south trail would proceed on the existing west-side gravel path from the cemetery entrance to the location of the failing Gabion north of Site 2, linking to rebuilt steps to the NW corner of the St. Clair bridge and to the existing stairs and path under the bridge up to the existing service road down from Avoca. A bridge across the stream from this location would take the proposed main trail to the east side, from which it would proceed along the route of the existing east-side path to a newly built path under the St. Clair bridge. The bridge and path construction should be integrated with the necessary streambed remediation to avoid unnecessary disruption of use by citizens.
Reach 2 (Report Figure 5, Appendix K-2) St. Clair Avenue road bridge to existing footbridge below Rosehill reservoir
North half: The proposed main north-south trail would continue south along the east bank of the creek, likely remaining at a relatively high level to avoid the wet area resulting from the reconstruction of Site 3. Two alternatives should be evaluated to implement the new trail taking into account property boundaries and the Report’s proposals for Site 4: (1) to rebuild the existing informal east-side trail between the stream and the very close property boundaries, (2) to take advantage of the west-side land created by the proposed relocation of the stream at Site 4 by routing the new trail across a bridge to the newly-created west side land. How this is resolved will depend on property boundary issues.
There may be an opportunity to widen the stream over part of this subreach sufficiently to create a pond that is both a visual enhancement and a provider of potential bird nesting areas, integrating a wetland habitat with the stream bank remediation.
Middle portion: The main issue here is the design of the stream remediation required to deal with the erosion resulting from the failed dam and stream walls at the location of the historic sawmill and spillway. The Geomorphic Study does not set out detailed proposals for how to do this. We see this as a potential viewpoint of interest in the ravine, with a bridge from the west side adjacent to the historic sawmill spillway across a potential pond to connect to the east- side trail down to the bridge below the reservoir. Where the main trail crosses back to the east side will depend on the choice set out above for the north half of Reach 2.
We should note that we see remediation of this area as a key priority, both because of the rapid undercutting of the ravine slope below the houses on Inglewood and because of the threat that the existing narrow trail above the undercut slope may make the existing informal trail unusable.
South portion: From the remains of the sawmill spillway down to the existing pedestrian bridge, the service road down from Avoca is being undercut by progressive streambed erosion. Remedial work — armourstone walls — will be required to protect the service road from slope collapse, but this work can be implemented without significantly impacting adjacent trails. The proposed main north-south trail meets the existing gravel trail to Mt Pleasant/Roxborough here.
Reach 3 (Report Figure 6) Bridge below reservoir to CP railway bridge
The major issue here is how to eliminate the erosion causing sink holes on either side of the existing pedestrian bridge. The existing east-side and west-side creekside trails both need to be preserved and improved.
Reach 4 (Report Figure 7) CP railway bridge to inlet to buried creek
Replacement of failed quarried block walls is required both for stream control and for preservation of existing west-side paths. Stream remediation should have no effect on the location of existing paths.
Adjacent access paths north of St. Clair
The currently closed steps down from the NW corner of the St. Clair bridge are an important potential access point from the Yonge/St. Clair neighbourhood and subway node. They need to be rebuilt, and this should be a priority. There is a severe slope collapse in the immediate neighbourhood of the junction of this access path with the proposed main north-south trail, where there is a major bank failure that may rapidly expand. This site should be identified as a priority for remediation, with reconstruction of the access path integrated with remediation of that part of the channel along with the report’s recommendations for dealing with Site 2.
Adjacent access paths in reaches 3 and 4, south of the footbridge
The Community Vision proposes an upgrading of existing access paths that access creek-side trails from the existing metal stairs down from Shaftesbury and Mathersfield, which currently end midway down the slopes — both to create safe all-weather access routes and to discourage off-trail usage. These proposals need to be integrated into an implementation plan for channel wall repair that minimizes disruptions due to construction.
4. Implementation priorities
The implementation recommendations were focused by the terms of reference on Toronto Water infrastructure and consequently do not deal with the necessity of dealing with other erosion issues in the ravine. Within the next ten years, the only erosion control recommended for implementation is that proposed for Site 4, including approximately 85 m of Gabion replacement between Site 4 and the St. Clair bridge. This is anything but a holistic view of the requirements in the ravine.
As the Geomorphic Study report makes clear (pp. 45-49), all four reaches of the open Yellow Creek stream are characterized by substantial slope undercutting and varying states of channel wall failure. While such failures do not threaten Toronto Water infrastructure, they do threaten both neighbouring properties and elements of the trail network, issues that are of importance to residents of the City if not to Toronto Water. And as such are erosion control issues that need to be remediated prior to or in conjunction with major investments in the trail network. It is clearly unacceptable, as the Study report implicitly proposes, to postpone all erosion control investments other than at Site 4 to sometime in the late 2030s or 2040s.
5. Conclusion
The Geomorphic Study report provides an invaluable compendium of data and analysis. As such, it provides the necessary technical underpinning for a Master Plan for the Vale of Avoca ravine. The challenge for the City and for neighboring stakeholders is to develop a holistic implementation plan that will speedily deal with all of the erosion issues identified by Geomorphic Study report as well as the related issues other than erosion control raised by the MRG Community Vision document.