Main – Guelph 1
Total Page：16
File Type：pdf, Size：1020Kb
MAIN – GUELPH 1 Region of Halton NAI Area # 7339 Credit Valley Conservation Authority Town of Halton Hills Size: 6 hectares Watershed: Credit River Con 9, Lot 18 Ownership: 98% Subwatershed: Silver private, 2% public Creek (Credit Valley Conservation) General Summary This is a small, urban natural area within the community of Georgetown. It is a naturally-vegetated remnant of deciduous forest cover along Silver Creek, as the creek flows through the town. Although small and impacted by several urban-related disturbances, this area still supports a provincially rare community, high fish biodiversity, herpetofauna and bats. This area plays a key role in maintaining vegetated cover and connectivity for wildlife movement along the Silver Creek valley corridor. It also plays a species-source role in a more diffuse connection, via urban forest cover, with other isolated natural patches nearby, separated by residential neighbourhood. NAI ELC surveyors inventoried vegetation communities and made incidental observations of flora and fauna, covering 100% of the natural area (Table 1). With respect to the NAI core inventories (vegetation communities, plants, breeding birds), this area is not considered data-complete. Full botanical inventory and breeding bird inventories remain as data gaps. Fish species were inventoried from both within the natural area and from upstream and downstream sampling stations. As there are no barriers between the upstream station and the natural area, and between the downstream station and the natural area, the data from these stations was extrapolated to the natural area and combined with on-site data. Table 1: NAI Field Visits Visit Date Inventory Type 19 June 1991 Fish 11 June 2006 Fish 10 Aug. 1994 Fish 27 July 2007 Fish 01 Sept. 1999 Fish 23 July 2008 ELC 30 Sept. 2003 Fish 24 July 2008 ELC 04 May 2004 Fish 22 July 2009 Fish Physical Features This natural area is in the Niagara Escarpment physiographic region: characterized by an escarpment that forms a significant break in the bedrock of the region. The escarpment has formed from the differing erosion rates of the bedrock layers, the softer lower shale layers eroding out from under the hard dolostone cap rock until portions of the cap rock collapse to form a cliff face and talus slope. In this general area, the escarpment cliff feature is buried by glacial deposits, producing a sudden rise in the land rather than a cliff face. The surrounding urban development of Georgetown has further obscured what was the natural topography around this site. As this natural area lies below the escarpment, the surrounding topography is relatively flat with only a gentle southward slope. Silver Creek passes through this natural area and is the main feature of the site. The creek has carved a ravine along its course and the presence of this ravine has likely contributed to preserving the natural vegetation of this site from development. Date of this Site Summary: October 2011 MAIN – GUELPH 2 Human History Georgetown was settled by George Kennedy circa 1819, who along with four of his brothers claimed land in the Georgetown area around the time it was surveyed. Early settlers opened mills along Silver Creek and the Credit River including a sawmill, grist mill, woollen mill and a paper mill. These mills supported the surrounding agricultural community. From this we can infer that logging, grain-growing and livestock-rearing occurred throughout much of the general area. Three railroad lines passed through Georgetown (Grand Trunk Railway, Hamilton and Northwestern Railway and Toronto Suburban Railway) and helped the community become a railway hub (Enright, Undated; Groundspeak Inc., 2010; Lewis, Undated). Historically, a large pond existed along Silver Creek within this natural area called Wilber (Wilbur) Lake. It provided water power to the Barber Brothers woollen mill as early as 1837. Construction of a wooden trestle for the Toronto Suburban Railway in 1915 resulted in filling or draining of a nearby connecting spring-fed pond and Wilber Lake dried up (McIlveen, 2006). The size of this natural area has been reduced by past land clearing for urban buildings on the valley slopes. Surrounding land uses are single residential, multi-unit residential, institutional (schools, youth centre, child care centre and church) and a small amount of commercial. Guelph St. (Highway 7), a major road, passes over Silver Creek and borders this natural area to the north. The south end of this area is bordered by Maple Ave. and Main St. At three points along these streets, narrow arms of the natural area extend directly to the roads, but generally, this neighbourhood and its landscaping is mature, effectively creating a broader area of connectivity with other urban tree cover across the streets and along the downstream naturally vegetated course of Silver Creek. Vegetation Communities The general community type present is deciduous forest (100%). A total of two vegetation communities of two different types were mapped over this natural area (Table 2). The Fresh-Moist Black Walnut Lowland Deciduous Forest community (FOD7-4) is provincially rare. Table 2: ELC Vegetation Communities Map Vegetation type Size in % of natural reference * hectares area Fresh-Moist Sugar Maple - Hardwood Deciduous FOD6-5 Forest 1.44 23.88 Fresh-Moist Black Walnut Lowland Deciduous Forest FOD7-4 PROVINCIALLY RARE S-RANK S2S3 4.60 76.12 TOTAL AREA INVENTORIED 6.04 * Note: The map reference code refers to the vegetation type shown on mapping for this area and also to the Appendix list of species typically encountered in this vegetation type. Species Presence Vascular Plants A total of 55 vascular plant species are recorded for this area as incidental observations, of which 38 (69%) are native. No species were At Risk, or provincially or regionally rare. These species were observed by the NAI ELC crew during their work, and it is believed that a full botanical survey of this area would reveal additional species. Date of this Site Summary: October 2011 MAIN – GUELPH 3 Fish A total of 18 species of fish were recorded, of which 15 (83%) are native. Brassy Minnow (Hybognathus hankinsoni) occurs at this site, one of only a few locations where this species has been detected in the Credit River watershed. This natural area supports mixed cool/cold water fish communities. Herpetofauna Herpetofauna were not inventoried, however, a landowner reported the presences of frogs and a turtle. Mammals Four native, common mammal species are known from incidental observations at this site, including a landowner report of bats. Site Condition and Disturbances This small natural area is comprised of mid-aged forest along the Silver Creek valley within an urbanized area of Georgetown. It experiences substantial urban impacts from surrounding land uses. Some of the surrounding buildings that back onto the ravine have large parking lots from which run- off drains directly into the creek. In some places, run-off channels have eroded deeply into the slopes and deposited large amounts of sediment along the floodplain. In addition to sediment, the run-off carries pollution from vehicles, road salt and other activities directly into the creek without chance for amelioration or absorption. Run-off is both regular and high-volume episodic and has altered the tree composition on the slopes by increasing the number of hydrophilic tree species. Non-native species are widespread and abundant. Notable problematic invasive species abundant here are Garlic Mustard (Alliaria petiolata), Common Buckthorn (Rhamnus cathartica), Manitoba Maple (Acer negundo), Norway Maple (Acer platanoides) and Periwinkle (Vinca minor). There is moderate widespread garbage and moderate widespread noise. Faint widespread trails sustain moderate recreational use. Ecological Features and Functions With forest communities greater than 2 ha, this natural area has the potential to support and sustain biodiversity, healthy ecosystem functions and to provide long-term resilience for the natural system. The riparian area provides a transitional zone between terrestrial and aquatic habitats, helping to maintain the water quality of the creek and providing a movement corridor for plants and wildlife. This natural area contains a provincially rare vegetation community and thus has the potential to support additional biodiversity above and beyond that found in common community types. The preservation of natural vegetation along this part of the Silver Creek valley serves the important function of maintaining a natural wildlife movement corridor through the urban setting of Georgetown. The vegetated valley corridor continues upstream to the north across Guelph St. In the downstream direction, to the southeast, linkage is more tenuous. Linkage corridors are narrow and across the busy roads, the Silver Creek corridor has been extensively developed for recreation, by manicuring and landscaping. There is more diffuse, but extensive connectivity with the urban forest cover in the mature neighbourhood to the southwest, which serves to connect other isolated natural areas with the Silver Creek corridor. The relatively close proximity of other areas of natural habitat creates above- average potential for wildlife movement between natural areas, species dispersal and recovery from disturbance, creating additional resilience for the ecosystem. Date of this Site Summary: October 2011 MAIN – GUELPH 4 Silver Creek, a major tributary of the Credit River, runs through this area and thus supports the connectivity function of the Credit River and its tributaries by providing a natural habitat corridor that facilitates the cross-regional movement of wildlife along this corridor between major provincial corridors. This natural area contains a provincially rare vegetation community. Based on the above feature, this area should be evaluated to determine if significant wildlife habitat is present in accordance with the Provincial Policy Statement. As an urban natural area, this site has aesthetic value to residents Opportunities An opportunity exists to improve the quality of this natural area by reducing the impact of run-off from surrounding parking lots and other pavement.