Smithville Master Community Plan
Subwatershed Study
A Subwatershed Study investigates natural features, natural hazards, and movement of water within and surrounding the existing and future development areas. It analyzes the impacts of urban development to the area’s wildlife, vegetation communities, groundwater, flood risk, and watercourses. These findings are the basis for developing a plan to mitigate these impacts, preserve the natural environment and protect existing development.
The Subwatershed Study team has reviewed all available background information and completed field investigations to develop a detailed understanding of the natural features and systems and their interdependencies. The field investigations were completed over the course of 2020 to assess the natural environment during various seasons, and included detailed investigations of the area’s:
- Groundwater
- Karst
- Surface Water
- Stream Morphology (Watercourses)
- Aquatic Ecology (Fisheries)
- Terrestrial Ecology (Vegetation and Wildlife)
- Climate Change
In 2021, the Subwatershed Study Team completed the first stage of the impact assessment to determine the effects of urbanization on the area’s natural and water resource systems, and on area karst features. In 2022, the Subwatershed Study Team completed the second stage of the impact assessment to evaluate alternative strategies and approaches to mitigate the impacts, and provide a recommended environmental and stormwater management plan. These assessments and recommendations have also incorporated measures to mitigate and manage the impacts of climate change.
Click on the links above or scroll down to learn about the details of the findings from these investigations.
.
Groundwater
It is important to understand the interrelationship between hydrogeologic conditions, ecosystem and use of groundwater for human needs, in order to assess and manage potential impacts from future land use changes on the groundwater flow system. In particular, it is important to identify and evaluate the functional relationship and interactions groundwater may have with existing surface watercourses and terrestrial resources.
- A significant amount of background information about the hydrogeologic conditions within the study area exists and has been reviewed. This review forms the basis for understanding groundwater setting and groundwater linkages.
- A groundwater field program, including groundwater level measurements and stream flow measurements, has provided additional information on groundwater flow trends and possible groundwater connections with stream reaches.
- Field observations and assessments from the other disciplines have been reviewed for indications of groundwater connections.
- Impacts of proposed development to groundwater recharge and baseflow have been assessed, and recommendations provided for mitigating these impacts.
- The study area is covered with a varying thickness of a clay overlying bedrock. The clay reduces the amount of water that can move downwards to the bedrock except where open fractures, rooting channels and animal burrows allow for greater movement of water. These pathways are more prevalent where the clay is less than six metres thick, which allows for more ‘recharge’ to bedrock.
- The underlying bedrock consists of a network of vertical and horizontal fractures and solution channels. The solution channels form when water moving through the fractures dissolves the rock. Water that moves through the clay enters into the bedrock flow system through these fractures and solution channels, generally moving horizontally from north to south in the shallow bedrock with a limited amount of groundwater discharging to Twenty Mile Creek. Groundwater also moves vertically to the deeper bedrock and follows similar fractures and solution channels. The fractures and solution channels that are more common in the upper 15 metres provide the water for most household wells outside the existing urban area.
- Stream reaches and wetlands that sit on top of the clay receive very limited amounts of groundwater compared to overland flow and direct precipitation.
- Areas where the clay is thin, six metres or less, allow for a greater potential for waterborne contaminants from ground surface to enter the bedrock groundwater system.
- Impacts from the proposed development can be mitigated by implementing Low Impact Development infiltration techniques, and redirection of groundwater flow along utility trenches may be mitigated by implementing anti-seepage collars or clay plugs.
- Dewatering activities must follow the guidelines provided by the MECP to address potential impacts related to the reduction in groundwater levels as well as water quantity and quality impacts related to dewatering discharge.
.
Karst
Karst is a geoscience that deals with the development of surface and subsurface landforms resulting from complex physical and chemical processes. Karst occurs only in certain types of rocks including limestone and dolostone (‘carbonates’), gypsum, and halite (rock salt). The carbonates are chemically dissolved by weak acids contained in rainwater, snowmelt, and soil seepage, forming sinkholes and pathways to move the water underground. This influences the water supply to natural features and systems. The information collected informs a hazard and constraint assessment, related to the geotechnical stability of the karst feature and bedrock.
- Several studies and historic air photos have been reviewed to identify potential locations.
- Field reconnaissance has been completed to confirm locations of karst features within and surrounding the study area.
- Impacts of proposed development to high constraint karst features have been assessed, and recommendations provided for mitigating these impacts.
- Ten karst features have been observed in the study area.
- Preliminary constraints to development from karst occur within three areas:
› Four features are considered low constraints, would not present a constraint to development.
› Two are considered moderate constraint and require further investigation to determine their contributions to the system and associated hazard.
› Two more are considered high constraint and are to be protected in-situ and buffered.
- Two additional features are located within the Twenty Mile Creek valley and are protected by virtue of their location.
- In all cases, additional runoff should not be directed toward sinkholes post-development; this can be achieved by implementing Low Impact Development practices to manage water budget to high constraint karst features, and diverting surplus runoff around/away from the feature.
.
Surface Water
The surface water assessment characterizes and evaluates the movement of surface runoff to natural wetlands, woodlands, watercourses, and karst features. This information is used to determine the change in the rate and volume of runoff following development, the associated impacts to flood and erosion hazard, and provides direct input to developing management strategies to mitigate these impacts from future development.
- Several reports and maps have been reviewed to understand the land use, soils, and storm infrastructure within and surrounding the study area.
- A monitoring program has been completed to collect local stream flow and rainfall data to better understand the runoff potential during storm events.
- Numerical computer models have been developed to represent the existing conditions in the area. These computer models have been used to test the impacts from future development, and the effectiveness of management strategies to mitigate these impacts.
- Floodline mapping developed by the NPCA established the flood hazard for regulated watercourses surrounding the study area. These are primarily located along the Twenty Mile Creek and North Creek, as well as a tributary of the Spring Creek located toward the east limit of the study area.
- Certain karst features within the area intercept surface runoff and convey it underground. Certain terrestrial features rely on the supply of water to sustain the ecology and habitat within the feature. The future development will need to manage the supply of water to these features.
- The area watercourses exhibit a moderate erosion sensitivity. The change in erosion sensitivity following development are being assessed as part of the impact assessment, and a strategy to mitigate these impacts will be developed accordingly.
- Impacts to erosion and surface water quality can be mitigated by implementing stormwater management practices for all future development in accordance with current Provincial and Municipal standards.
- Flood impacts can be mitigated by implementing stormwater management quantity controls throughout the development within the Spring Creek Subwatershed, and at strategic locations within the areas draining toward the Twenty Mile Creek and North Creek, as well as implementing Low Impact Development Best Management Practices to maintain existing groundwater recharge.
- Impacts to water budget can be mitigated by implementing Low Impact Development Best Management Practices throughout the future development.
- Conceptual stormwater management facility locations have been identified within the future land use plan, which are to be further refined as part of the next phase of the Subwatershed Study and subsequent stages of planning and design for the future development areas.
Figure 1: This equipment was installed to collect stream flow data for the study area. The data collected has been used to determine the runoff potential from storm events. This information has provided a basis for determining how runoff potential would change as a result of development and the stormwater management plan to mitigate these impacts.
Figure 2: Stormwater management facilities are currently provided within the existing development areas of Smithville. These facilities are intended to provide stormwater quality control to remove pollutants from storm runoff, and some others are also designed to provide quantity control for flood protection and erosion control for receiving watercourses. This information provides insight regarding the current practices within Smithville, and the requirements and opportunities for stormwater management within the future development.
Figure 3: The Niagara Peninsula Conservation Authority (NPCA) has developed flood hazard mapping for regulated watercourses within its jurisdiction. The flood hazard mapping determines the flood risk to properties, and informs determining the limit of future development. The analyses completed for the Subwatershed Study has built upon this information from the NPCA and has been used to determine the change in flood potential following development, as well as the effectiveness of the stormwater management plan in mitigating these impacts.
.
Stream Morphology (Watercourses)
The purpose of the stream morphology study is to identify and characterize surface water features within and downstream of the study area to evaluate sensitivity to development, and to limit risk to settlement areas from watercourse erosion hazards. The results of the study are used to provide guidance to proposed land use changes to ensure that existing channel dynamics continue unimpeded by development, and to ensure that any potential impact to downstream channels is minimized.
The study has included:
- A background review of previous studies, guidance documents and mapping. This included a review of historic photographs dating back to 1934. Using available mapping, features were delineated into reaches, which are lengths of channel that exhibit similar characteristics.
- The meander belt width, which is the area that a watercourse currently occupies or can be expected to occupy in the future, was mapped for each watercourse reach. Erosion hazard limits were also mapped for Twenty Mile Creek which flows through a defined valley.
- A field assessment of watercourse reaches within and downstream of the study area. Channel health and function, size, bank and bed materials were assessed. As well, watercourse stability was assessed based on evidence of channel widening, downcutting (degradation), sediment build-up (aggradation) and meandering.
- Three sites that were identified as sensitive to erosion were studied in greater detail to determine the flow characteristics that could trigger erosion. These flow characteristics differed between each site because of differences in watercourse size and shape, bed and bank material, slope and vegetation. The three sites were distributed across the three subwatersheds within the study area.
- Headwater drainage features (HDF) – non-permanently flowing drainage features that may not have defined beds or banks, such as swales (shallow, vegetated channels) - were assessed following established guidelines. The assessment involves three site visits in the spring and late summer to determine the role of each feature in terms of hydrology, riparian vegetation (vegetation along river networks) and fish habitat.
- Impacts from the proposed development have been assessed, and recommendations to mitigate these impacts to the area streams and watercourses have been provided.
- The study area intersects the North Creek, Spring Creek and Twenty Mile Creek watercourse corridors. The study area also contains several watercourse tributaries to Twenty Mile Creek and North Creek, and over 180 headwater drainage features.
- The historical assessment indicated that watercourse meandering has been fairly limited since 1934 inside the study area. As well, some reaches within and downstream of the study area have been historically altered.
- Most watercourse reaches were found to be in a moderate or poor state of overall health and function. Sediment accumulation (aggradation) and channel widening were some of the more common types of channel adjustments within the study area.
- Twenty Mile Creek is the most significant watercourse and valley system within Smithville. North Creek is the second most significant watercourse in the vicinity of Smithville. It is generally unconfined within the study area and has a well-defined floodplain. Spring Creek near the study area generally does not have a well-defined channel and is located in a wide floodplain.
- Surface water features are influenced by karst. One tributary and two headwater draining features (HDFs) were observed to enter sinkholes.
- Many HDFs have been impacted by agriculture. They supply fine sediment to the downstream drainage network.
- Several HDF features are found within or provide linkages to wetlands.
- Using information from the larger interdisciplinary study team along with the results of the stream morphology study, preliminary constraint rankings were given to each HDF and watercourse feature in the study area. These rankings are being confirmed, and management implications associated with the constraint rankings will be outlined as part of the impact assessment.
- Watercourses within the study area do not always flow year-round. This allows vegetation to establish inside some channels.
- Impacts of the proposed development to watercourse erosion can be mitigated by incorporating erosion controls within the stormwater management facilities.
- Regulated watercourses can be managed by appropriately sizing watercourse corridors for natural channel meander and flood conveyance, properly sizing watercourse crossings (bridges and culverts) to maintain channel form and function, maintaining natural cover along watercourses, and rehabilitating degraded watercourses.
.
Aquatic Ecology (Fisheries)
It is important to identify and characterize the aquatic features and fish community within the study area, such as permanent and intermittent features and fish habitat suitability to properly assess their significance, individually and as a part of the overall landscape, in order to protect their form and function. Fish habitat is protected.
Field surveys conducted throughout 2020 include:
- Aquatic habitat characterization;
- Fish community surveys;
- Thermal regime analysis; and,
- Fish Habitat Type classification.
- Twenty Mile Creek and North Creek provide year-round fish habitat within the study area, which supports a diverse fish community comprised of warm and coolwater fish species, including recreationally valuable top-predator species such as Northern Pike, Largemouth Bass, and White Crappie. Intermittent watercourses and HDF are also present.
- Twenty Mile Creek and the intermittent watercourses are classified as cool-warmwater features and North Creek is classified as a coolwater feature based on summer water temperature measurements and the temperature preferences of the fish species that were captured within them.
- Twenty Mile Creek and North Creek both provide critical fish habitat year-round, though sections of the creeks do become dry in the summer. Intermittent features and HDF that were noted to contain fish in the spring provide important seasonal habitat for the local fish community and also provide indirect benefits to the larger creeks. The remaining features across the study area provide habitat to a limited number of species but do provide some indirect benefits to the larger creeks as well. Intermittent watercourses and HDF become dry in the summer and do not provide fish habitat during that time.
.
Terrestrial Ecology (Vegetation and Wildlife)
It is important to identify the terrestrial features and wildlife within the study area, such as woodlands, wetlands, plants, and animals to properly assess their significance, individually and as a part of the overall landscape, in order to protect their form and function. Significant natural heritage features and Species at Risk are protected in Ontario.
- Field surveys conducted throughout 2020 include:
› Plant surveys and vegetation community identification;
› Breeding bird surveys;
› Anuran (frog and toad) surveys;
› Snake cover board surveys;
› Wildlife surveys; and,
› Wildland Fire Hazard Screening.
- Integrated Natural Heritage System developed to protect, enhance, and restore the natural environment.
The study area includes many significant wetlands, significant woodlands, significant wildlife habitat, and Species at Risk. Significant wetlands within the study area make up part of the much larger Lower Twenty Mile Creek Wetland Complex, which extends across the study area and includes areas along Twenty Mile Creek and North Creek.
Significant wildlife habitat includes:
- Deer wintering habitat;
- Wetland amphibian breeding habitat;
- Terrestrial crayfish habitat;
- Reptile hibernacula;
- Turtle wintering and Snapping Turtle habitat; and,
- Habitat for Species of Conservation Concern, such as:
› Eastern Wood-Pewee;
› Lizard’s Tail;
› Black Gum; and,
› Hirsute Sedge.
Significant species found include:
- Barn Swallow;
- Bobolink;
- Eastern Meadowlark;
- Eastern Wood-Pewee;
- Monarch;
- Snapping Turtle;
- Lizard’s Tail;
- Black Gum; and,
- Hirsute Sedge.
The lands have been classified as low to moderate risk for wildfire based on low proportions of coniferous trees within woodlots and across the study area.
A Natural Heritage System has been identified within the study area based on existing policy, a background review, and field surveys.
Other opportunities to mitigate impacts from future development include:
- Implementation of a robust Natural Heritage System;
- Developing tree protection plans to minimize tree removal and harm;
- Timing vegetation removal avoiding the active season of wildlife (esp. bats, migratory birds);
- Conducting appropriate surveys as necessary if vegetation removal is to occur during the wildlife active seasons (e.g. bat acoustic surveys, bird nest searches in simple habitats);
- Complying with Endangered Species Act requirements and permitting where necessary;
- Implementing compensation for wildlife habitats directly removed;
- Implementing Low Impact Development Best Management Practices into stormwater management plans;
- Sizing road crossings to accommodate wildlife passage; and,
- Public education.
.
Climate Change
- All levels of government recognize climate change as having the potential to affect almost every aspect of our lives, including human health and well-being and environmental impacts.
- Climate change is recognized to be a result of greenhouse gas emissions (CO2, CH4, N2O, water vapour).
- The projected changes in climate are recognized to increase risk for Canada’s ageing infrastructure, causing structural damage, compromising system reliability and threatening health and safety.
- Provincial and Regional policies require municipalities to consider the potential impacts of climate change as part of natural environment planning in order to better protect the natural environment system and reduce economic costs.
Anticipated impacts of climate change within Niagara Region:
- Increase in annual average temperature
- Trend towards more days with temperatures over 30°C and more heat waves of 3 or more consecutive hot days
- Longer growing season, with May and September significantly warmer
- Increase in average number of frost-free days
- Increased numbers of freeze-thaw cycles
- Small increase in annual precipitation, with most of the increase coming in winter
- More rain and less snow in winter
- More summer droughts and dry spells
- Increase in heavy rain events
The specific magnitude of impact/ change is still uncertain, however the anticipated impacts are supported by observations and analysis and result in significant economic and health impacts.
- There is a correlation between actions that reduce greenhouse gas (GHG) emissions (climate change mitigation) and actions that build resilience to deal with climate change impacts (adaptation).
- Nature-based solutions and mitigation measures – such as forests and wetlands, working landscapes, and other open spaces that conserve or enhance ecosystem values and functions – also mitigate water-related impacts of climate change.
- Green infrastructure and nature-based adaptation methods such as green roofs, bioswales, bioretention ponds, rain gardens, and vegetative swales are recognized to reduce the risks from stormwater runoff.
- Green spaces and infrastructure, such as parks, wetlands and green roofs increase the quality of life for residents and improve climate resilience.
- These methods, combined with more traditional stormwater management measures – such as wet ponds for flood control and incorporating natural channel design into watercourse corridor designs – would reduce the risks from riverine flooding and enhance resilience of infrastructure to impacts from climate change.
- Mitigation measures proposed for Smithville include the following which would contribute toward mitigating and managing the impacts of climate change:
› Incorporating Green Infrastructure and Low Impact Development Best Management Practices into the stormwater management plan promotes resiliency and enhances stormwater quality, erosion, and quantity control.
› Providing green spaces – such as parks and wetlands – reduces heat effects and provides additional opportunities for incorporating Green Infrastructure into development.
› Planning for a robust Natural Heritage System, including linkages and enhancement areas, actively reduces harmful greenhouse gas emissions, mitigates heat effects from urban development, and maintains water budget.
Provide Feedback
We want to know what you think about the Smithville Master Community Plan!
To provide feedback on the MCP, including the draft Preferred Concept Plan, key policy directions and draft Official Plan Amendment No. 62 and 63, please click the link below.
Next Steps
The MCP Project has recently completed Phase 3 of its timeline, following the completion of the Preferred Concept Plan and the Monitoring, Management and Implementation Recommendations in consultation with review agencies, stakeholders and the public.
To learn more about what’s coming up for the Project and how you can be a part of the ongoing consultation, please click the link below.