Grindstone Creek Escarpment Valley

General Summary

This study area encompasses the steep-sided valley of Grindstone Creek as it descends the Niagara Escarpment and crosses the south slopes. The valley extends for approximately 4 km, dropping from 235 m elevation along the brow of the Niagara Escarpment in Waterdown, to 100 m at the Highway 403 crossing, but only the upper portion is within the City of Hamilton. The sheltered, southerly exposure of this site results in a relatively warm, dry microclimate that supports many Carolinian and southern plants, including rare and uncommon species.

Significance

Ontario Ministry of Natural Resources Designation:
• Provincial Life Science ANSI (Area of Natural and Scientific Interest)
• Provincial Earth Science ANSI (Area of Natural and Scientific Interest)

City of Hamilton Environmentally Significant Area (ESA) Criteria:
• Significant Earth Science Feature

• Significant Ecological Function

• Significant Hydrological Function

Physical Description

The upper portion of the Grindstone Creek Escarpment Valley encompasses a pre-glacial notch cut into the southwest-northeast trending Niagara Escarpment. Provincially significant bedrock exposures within the deeply dissected escarpment valley include Queenston, Whirlpool and Manitoulin Formations at the Grindstone Cascade, as well as Manitoulin, Cabot Head, and Lockport Formations exposed in the creek bed.

Groundwater movement in the vicinity is generally southerly into Hamilton Harbour. Bedrock aquifer discharges along the escarpment face appear to contribute significantly to the baseflow of Grindstone Creek, which changes from a warmwater to a coldwater stream as it descends the escarpment. Below the escarpment, it forms a fast, actively-eroding stream in a V-Shaped valley. The natural vegetation on the ravine slopes moderates the rate of erosion, while the vegetation on the valley bottom slows and filters surface runoff.

Ecological Land Classification

This natural area consists of a core strip of wooded floodplain bordered by wooded ravines. Except for two small open marshy areas, the floodplain generally consists of mesic to wet-mesic broadleaf woods. The ravine slopes are characterized by very steep slopes with a mesic to dry-mesic moisture regime with broadleaf and mixed woods. Successional and maintained communities are locally present within the valley system.

Flora and Fauna Summary

Vascular Plants

Because this area includes southern exposures and relatively warm, dry climates, many Carolinian, prairie/savannah, and southern species can be found at this site. Field inventories from 1977 to 1999 documented 47 significant species, including two COSEWIC listed species, American Columbo (Frasera caroliniensis) and Red Mulberry (Morus rubra).

Butterflies

In 1990 and 1991, twelve species were documented including two locally uncommon species and one locally rare species, Northern Cloudy-Wing (Thorybes pylades).

Fish

Twenty-one species in total have been documented here since the 1970s, with thirteen species recorded since 1990. Rainbow Darter (Etheostoma caeruleum), Stonecat (Noturus flavus) and Finescale Dace (Phoxinus neogaeus) are significant species that have been sampled since 1990 within these reaches of Grindstone Creek. The escarpment waterfall at Smokey Hollow is a barrier to upstream fish movement which only Rainbow Trout (Oncorhynchus mykiss) have been able to ascend to form a self-sustaining population.

Herpetofauna

Due to inadequate survey work, only one common species was recorded in 2002.

Breeding Birds

Nature Counts surveyors recorded 42 species in 2002 including 11 locally uncommon species and three interior forest species.

Mammals

The Nature Counts project conducted small mammal trapping in August of 2002. Nine common species were recorded all of which are new records for the area.

Waterfalls

 

• Great Falls
• Grindstone Cascade
• Snake Falls
• Hidden Grindstone Falls