CGRG Bibliography of Canadian Geomorphology
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Author : Frizzell, R.; Usher, S.J.; and Palmer, R.S.
Date : 2005.
Title : Small sand lenses, large impacts – the effects of glacial geology on sensitive ecological features.
Publication : Joint Meeting of the Geological Association of Canada, the Mineralogical Association of Canada, the Canadian Society of Petroleum Geologists and the Canadian Society of Soil Sciences. May 15-18, 2005. Studley Campus of Dalhousie University, Halifax, Nova Scotia.
Issue :
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Abstract
Rapid development in sub-urban and rural areas of southern Ontario has placed significant pressures on the provinces dwindling natural areas. For example, the impact of construction dewatering and longer-term development has led to a variety of impacts to shallow aquifers, wetlands and surface water features such as headwater streams. The key to preventing and mitigating impacts to the natural environment is to develop a strong geological framework that can be used to predict groundwater and surface water interactions. This requires an understanding of glacial depositional systems and the variability that can exist within these sediments. Determining the natural function of glacial deposits requires a combination of geology, hydrogeology, fisheries biology and terrestrial ecology. Discrete or small-scale permeable quaternary sediments are important sources of groundwater baseflow to streams and wetland habitat. Protection of significant ecological features is required under the Ontario Provincial Policy Statement and potentially under the proposed Drinking Water Source Protection Act, which is primarily designed to protect groundwater resources. The health of sensitive natural areas and quality of the groundwater, however, are directly related. In many cases the surficial till and fine lacustrine sediments covering much of southern Ontario inhibit rapid groundwater movement. Only where permeable surficial and/or shallow buried sand to sand and gravel deposits are present within the till cover is there localized lateral groundwater flow to creeks and wetlands. Subtle variability in Quaternary stratigraphy, however, makes it difficult to accurately predict the geology between adjacent geotechnical and exploration boreholes. Discrete sand lenses on the scale of 100 m by 200 m is size for example, are often missed by boreholes and almost certainly not predicted by large-scale groundwater models. Yet, these small deposits have been shown to support important or threatened aquatic and terrestrial habitat. In addition to geological investigations, detailed field studies of the local aquatic environment and terrestrial plant species provide important clues as to the presence of discrete, permeable geological features. Using these combined studies it is possible to predict and map the distribution of these glacial deposits. By examining several high profile construction projects as case studies, we can demonstrate how impacts to the natural environment can be predicted and avoided using a multidisciplinary field investigation.
Bibliography of Canadian Geomorphology