What is a watershed?

What is watershed planning?

  • Watershed planning provides a framework for establishing goals, objectives, and direction for the protection of water resources, the management of human activities, land, water, aquatic life, and resources within a watershed.
  • Watershed planning is required by Provincial Plans, including the Provincial Policy Statement, the Greenbelt Plan and the Growth Plan, to identify and protect natural resources and areas, and to help inform future land use planning decisions.
  • The Regional Official Plan (ROP) also recognizes the preparation and implementation of Watershed Plans as an effective planning tool in the protection of natural heritage resources.

Where is the Carruthers Creek watershed located?

  • The Carruthers Creek watershed is located within the City of Pickering and Town of Ajax and is on the eastern edge of the Toronto and Region Conservation Authority (TRCA) jurisdiction. The watershed is approximately 38 square kilometres (km) in size, ranging from 2 to 3 km in width, with a total length of 18km.
  • The headwaters form to the south of the Oak Ridges Moraine, in the City of Pickering, and the creek enters Lake Ontario in the Town of Ajax at Carruthers Marsh.

Is this the first watershed plan for Carruthers Creek?

  • No, a watershed plan for Carruthers Creek was completed in 2003, at the same time as Duffins Creek. The 2003 Duffins and Carruthers Creek Watershed Plan evaluated existing watershed conditions and identified recommendations to protect, restore, and enhance the natural systems and water quality of both watersheds. The issues identified in the 2003 plan are still prevalent in the watershed.

Why was an updated watershed plan for Carruthers Creek necessary?

  • Periodic reviews of watershed plans are an integral component of the watershed planning process and allow for adaptive management to incorporate new scientific approaches and to address emerging initiatives.
  • Since 2003, the Carruthers Creek watershed has experienced significant changes associated with urbanization and the impacts of climate change. Since many of the issues identified in the previous watershed plan are still occurring, an updated watershed plan using the latest advancements in watershed science, monitoring programs, and computer modelling was necessary.
  • Additionally, Policy 7.3.11 p) of Durham’s Regional Official Plan (ROP) states that the completion of a watershed plan update for Carruthers Creek watershed is a precondition to the consideration of future development in northeast Pickering (determined through the Municipal Comprehensive Review (MCR)).

How was the Carruthers Creek Watershed Plan developed?

  • In 2015, the Region of Durham engaged TRCA to develop a watershed plan for Carruthers Creek. The development of the plan was a multi-year process that included:
    • Field work to identify existing watershed conditions that culminated in eight, peer-reviewed watershed characterization technical reports
    • Potential future scenarios modelling and analysis that culminated in eight, peer-reviewed scenario analysis technical reports
    • Identification and mapping of the Water Resource and Natural Heritage Systems
    • Development of a management framework for the protection, enhancement and restoration of watershed health. The framework consisted of goals, objectives, indicators and management recommendations
  • See subsection 1.2 in the draft Carruthers Creek Watershed Plan for more information.

Was there public consultation throughout the watershed planning process?

  • Since project initiation, the CCWP has been a highly consultative and collaborative process that followed the CCWP Communications and Consultation Strategy. The goal of consultation was to raise awareness of the watershed planning process in addition to seeking input and feedback.
  • Consultation activities included a project website, dedicated project e-mail address, online surveys/comment forms, pop-up displays at community events, stakeholder workshops, presentations to municipal Committees, Councils, and advisory committees, and Public Information Centres.
  • Information on consultation activities is available on the Reports and Resources tab of the project webpage.

What is the timeline of this Watershed Plan?

  • This plan is intended to be in effect for ten years from when it is finalized and approved.
  • Through regular reporting and adaptive management, the plan may be modified to address changing circumstances.

Who is responsible for the development of the Carruthers Creek Watershed Plan?

  • As outlined in the Growth Plan, upper and single-tier municipalities (in partnership with lower-tier municipalities and Conservation Authorities) are responsible for watershed planning. The Region of Durham commissioned the study to satisfy Growth Plan requirements and Regional Official Plan policy.
  • TRCA is undertaking the completion of the watershed plan in collaboration with Durham Region because of its technical expertise and knowledge of the watershed, and experience in watershed planning.
  • The Carruthers Creek Watershed Plan is viewed as a collaboration between the Region of Durham and TRCA, with participation from Town of Ajax and City of Pickering staff.

Who is responsible for the implementation of the Carruthers Creek Watershed Plan?

  • TRCA, the Region of Durham, and area municipalities all play a role in the implementation of the Carruthers Creek Watershed Plan. Some of the Plan’s management recommendations identify specific stakeholders that will need to implement the recommended action(s).

Does the Carruthers Creek Watershed Plan decide on future land use?

  • Watershed plans are not land use plans, nor do they constitute a land use planning decision. The data, scientific analysis, modelling, scenario evaluation and management recommendations generated through a watershed planning process is used by municipalities to inform land use and infrastructure planning decisions.

What is the rationale for the proposed enhanced Natural Heritage System (NHS) in the Carruthers Creek Watershed Plan? Why is it so big? Is it realistic?

  • The size of the proposed enhanced NHS is more consistent with federal guidance on how much habitat is necessary to maintain ecological functions and biodiversity. The proposed enhanced NHS being recommended achieves 36% natural cover in the Carruthers Creek watershed, consisting of 16% forest, 7% wetland, 3% meadow and 9% successional (young forest). Federal guidance recommends at least 30% forest cover at the watershed-scale. Achieving this federal target is challenging in an urbanized watershed. However, the proposed enhanced NHS represents a realistic and attainable system for the Carruthers Creek watershed.
  • The proposed enhanced NHS is consistent with the Provincial Policy Statement (PPS), which encourages the maintenance, restoration and improvement of the diversity and connectivity of natural features to protect long-term ecological function and biodiversity (PPS, 2014, policy 2.1.2). The Growth Plan provides the flexibility for upper-tier and single-tier municipalities to refine provincial mapping of the Natural Heritage System for the Growth Plan, and includes policy provisions to continue natural heritage system planning that is consistent with the PPS (Growth Plan, 2019, policies and
  • The proposed enhanced NHS uses the latest updated science and practices in natural systems planning. TRCA’s Terrestrial Natural Heritage System Strategy (TNHSS, 2007) recommends that at least 30% natural cover be achieved across TRCA’s jurisdiction in order to maintain regional biodiversity in the long-term. The proposed enhanced NHS builds off the 2007 TNHSS and uses the latest data, science, and modelling approaches to include consideration of:
    • Priorities for local and regional connectivity (e.g. wildlife movement)
    • Priorities for climate change adaptation in highly vulnerable areas (protecting the highly vulnerable areas) to build a resilient system in the long-term
    • Priorities for enhancing habitat size and configuration for maintaining habitat quality and biodiversity (habitat patch size and configuration are vital to good quality habitat)
  • See section 2 and goal 3 (subsection 5.3) in the draft Carruthers Creek Watershed Plan for more information.

What happens if a development option includes a smaller/different enhanced Natural Heritage System?

  • The proponent would be required to demonstrate how any proposed alternative would maintain the intent of the Carruthers Creek Watershed Plan, including the goals related to the long-term health and sustainability of the watershed.
  • The scenario analysis conducted for the Carruthers Creek Watershed Plan shows potential negative impacts on the proposed enhanced NHS even at its size and configuration. For example, under the full Whitebelt build-out scenario (Scenario #3), the matrix influence (influence of surrounding land uses) demonstrates declining habitat quality trends. Significant modifications to the size and configuration of the NHS could exacerbate these impacts and lead to further degradation of remaining natural systems.

What is the Water Resource System and why is it important?

  • The Water Resource System is all the groundwater and surface water features, areas and functions within the watershed that provide the water resources necessary to sustain healthy aquatic and terrestrial ecosystems and human water consumption.

What are the significant issues in the watershed?

  • Based on the technical assessments completed by TRCA as part of watershed characterization (i.e. existing conditions), there are four key issues in Carruthers Creek:
    1. The aquatic ecosystem is sensitive and near the level of land use development it can sustain long-term (without additional and improved mitigation). This is due primarily to high levels of impervious cover due to urbanization and instream barriers to fish movement.
    2. There is not enough natural cover, or good quality habitat, needed to maintain ecosystem resilience (i.e. capacity to respond to change). Approximately 25% of the watershed is natural cover and overall habitat conditions are poor.
    3. Water quality is impaired within the watershed requiring improvements to stormwater management. Elevated concentrations of phosphorus, total suspended solids, chlorides and E. coli are particularly problematic.
    4. The flow of water through the watershed is out of balance and there are flooding and erosion issues. There is currently a flood vulnerable cluster in the lower part of Carruthers Creek within the Town of Ajax.
  • See subsection 3.3 in the draft Carruthers Creek Watershed Plan for more information.

What is scenario analysis and why is it valuable?

  • Scenario analysis is a technical exercise typically undertaken when developing watershed plans to ensure management recommendations are based on the best available science.
  • By comparing different possible land use configurations, assessment of how the watershed will respond can be undertaken.
  • For this Watershed Plan, three potential future land use scenarios were assessed:
    • Scenario 1 (Official Plan), which assumed all lands south of the Greenbelt are developed up to 2031 based on approved Official Plans.
    • Scenario 2 (+NHS), which assumed the same development as scenario 1, but includes the proposed enhanced Natural Heritage System.
    • Scenario 3 (+Potential Urban), which assumes development in the headwaters of Carruthers Creek (north of the Greenbelt), outside of the enhanced Natural Heritage System.
  • See subsection 4.2 in the draft Carruthers Creek Watershed Plan for more information.

What conclusions can be drawn from the scenario analyses?

  • Protecting, enhancing, and restoring natural areas throughout the watershed provides benefits as illustrated by Scenario 2.
  • Limiting impervious cover in any potential future development, provides benefits to aquatic ecosystems.
  • The management framework developed as part of this watershed plan contains recommendations to improve watershed conditions regardless of potential future land use decisions.

Looking at the hydrology scenario analysi, and the associated increase in peak flows under Scenario #3, doesn’t it conclude that any development of the headwaters would be detrimental to the watershed?

  • The hydrology model results show that development in the northeast Pickering headwaters area (Scenario #3) will result in a significant increase in peak flows throughout the watershed. This modelling does not factor in potential mitigation measures (e.g. stormwater management and distributed low impact develop measures). However, this finding does not preclude the possibility of development in northeast Pickering.
  • Should the lands in northeast Pickering come into the Urban Area boundary, TRCA staff believe an engineering solution may be feasible, subject to developing a satisfactory engineering solution through further study at the appropriate stage of the planning process (i.e. a secondary plan).

How would development proceed in the headwaters of Carruthers Creek should it be allowed by the Region of Durham?

  • The lands within the headwaters of Carruthers Creek are not designated as part of the settlement area of the City of Pickering or the Region of Durham’s urban area boundary. For development to proceed, a Settlement Area Boundary Expansion (SABE), in accordance with the applicable policies of the Growth Plan, would need to occur.
  • If the Region of Durham determines that a SABE is necessary in the headwaters of Carruthers Creek specifically, subwatershed planning (or equivalent) would need to demonstrate that the key hydrologic features will be protected, appropriate mitigation measures are in place to maintain hydrologic function for key hydrologic areas, and that there will be no negative or adverse downstream effects.

Can TRCA recommend that the headwaters of Carruthers Creek be added to the Greenbelt?

  • The role of TRCA is to provide scientific information and analysis to guide the development of management recommendations, which help inform future municipal land use decisions. Municipal governments decide where and how development occurs. Currently the provincial government is not considering an expansion of the Greenbelt.
  • TRCA supports the protection and expansion of natural areas for the long-term health and resiliency of the watershed. The Greenbelt is one part of Ontario’s land use planning framework. The recommended enhanced NHS in the Carruthers Creek Watershed Plan is another planning tool that allows municipalities to decide, at the local level, the extent and distribution of natural areas.

How will progress on plan implementation and watershed conditions be monitored or tracked?

  • There are a series of monitoring stations distributed throughout the watershed to monitor aquatic and terrestrial species, water quality, groundwater, and water quantity (i.e. the flow of water). These stations will allow TRCA to track watershed conditions over time for the duration of the plan to determine trends. See section 6 in the draft Carruthers Creek Watershed Plan for more information.