Summary Report and Implementation Plan - Partners in Project Green

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entire Etobicoke Creek watershed. This indicates the GTAA study area contributes immensely to the overall health of the natural system within the watershed. • The state of the terrestrial system within the GTAA study area was evaluated as “poor” to “very poor” during the landscape analysis. This is not surprising given the matrix influence of airport operations and major transportation corridors. • Surrounding any habitat patch is a matrix of land-use types, ranging from agricultural to urban uses, which influence the ecological function of the system. Adjoining natural cover is beneficial, while urban uses often exert a strong negative influence, such as hydrological change, introduction of invasive species, and trampling and collection by local citizens. • The majority of habitat patches in the study area receive a “poor” to “fair” score for both patch size and shape. The GTAA study area does provide for a lot of natural cover; however, little forest interior (100 metres from forest edge) exists. • Distribution of habitat and natural cover is weighted to the north, with serious deficiencies in the south. The south cannot support appropriate species of concern in its urban matrix, thus any change in higher quality portions in the north should be considered to what has already been lost. • Only one patch features forest interior in the GTAA study area. Located south of Highway 401, it supports the highest diversity of flora and fauna species of conservation concern, and is the least disturbed within the study area. The existence of this patch demonstrates large habitat patches with good shape can continue to support sensitive species in an urbanized environment. • Aside from riparian linkages, connectivity between other natural patches in the GTAA study area are insufficient for the maintenance of terrestrial species and ecological services. • Priority Candidate Restoration Sites identified and ranked from high to low, based on ecological gains to the terrestrial system and immediacy for action. These Candidate Restoration Sites are included in Appendix 1 and are spatially related on Map 3. Stormwater Management One of the biggest issues facing the Etobicoke Creek is stormwater management (SWM). Significant portions of the watershed were developed prior to SWM practices and in some places uncontrolled discharges go directly into the creek, leading to degraded water quality and increased erosion. Restoring native vegetation communities is a key component of rebuilding a sustainable natural heritage system that has begun to fail after suffering decades of cumulative losses, and the impacts of human use and development.
GTAA Living City Project Integration Etobicoke Creek and Implementation Watershed Discussions with GTAA staff have revealed that there are very limited stormwater retrofit opportunities on GTAA lands. Approximately $150 million has been invested over the last several years on numerous water quality enhancement projects, including state-of-the-art underground treatment tanks, a two-celled treatment wetland and many other associated structures. There are few, if any, remaining feasible retrofit opportunities for effective stormwater management. As a result, the study of on-site retrofit projects was not advanced. A number of studies contribute to this report and were conducted from a variety of spatial scales, from site-specific to catchment to reach and watershed, and are spatially interpreted on Map 4. These studies and their key findings include: • Toronto and Region Conservation Hydrology Update – an update of the Etobicoke Creek hydrology model to a continuous model that identifies existing flow rates, volumes of runoff, future condition rates and volumes based on projected development scenarios. new wet pond location has been identified for construction through the Catchment 219 Study within the City of Mississauga and three ponds were identified for retrofit within the City of Brampton. In addition, 15 outfalls have been identified for retrofit within the City of Brampton and five in the City of Mississauga. • Spills Mapping Study – most oil and chemical spills occurred in industrial areas of Brampton and Mississauga, with spill hot-spots being the areas upstream of GTAA lands bounded in the west by Highway 401, Highway 410 and Derry Road, and to the north by Dixie Road and Highway 407. Due to presence of sand-clay and clay-loam soil in the watershed, groundwater pollution associated with the soil-impact spills may not be very significant. Human error and equipment failure were the primary reasons for the spills. • Fluvial Geomorphology Study and Erosion Assessment – data from 18 detailed study sites found that in the upper part of the watershed, the critical discharge values represented flow conditions well above bankfull conditions, while the lower reaches of the watershed experience erosive flow conditions much more frequently. These results will be used for a number of different purposes including siting of valleyland restoration projects, assessing erosion-prone areas for remediation works and, in the short term, this information can be used to prioritize stormwater management retrofit opportunities to maximize erosion control benefits. • Stormwater Management in the Watershed – the cities of Brampton and Mississauga have both undertaken retrofit studies that identify existing stormwater management ponds and uncontrolled storm sewer outfalls where it is feasible to implement works to enhance quality and quantity. Upstream of the GTAA lands, a Porous pavement. 10
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