Environmental Sensitivity Analysis: A Regional Examination in Alberta, Canada.

Kim Hodge and Neil Gilson

Abstract

This study examined the utility of using limited datasets to delineate environmentally sensitive areas in a rural municipality (M.D.) in Alberta, Canada.The subject M.D. spans an extremely diverse ecological community along the eastern slopes of the Canadian Rockies, is located adjacent to a major urban community and is subject to intense development pressures. Limited, existing, ecological data were overlaid to delineate environmentally sensitive "hotspots".Hotspots were compared to existing ecological, biodiversity and wildlife habitat data and to current patterns of development. Project outputs provide useful planning information appropriate for identifying areas of concern, scoping environmental issues, and guiding further analysis and study.

 
1.0 Purpose
The purpose of the project was to develop a planning tool that could be used by the M.D. of Foothills Environment Committee and Planning Departments to identify natural resources and ecosystem components of environmental, economic and social importance, that may be sensitive to the potential impacts of proposed developments.  Specifically, to develop a GIS methodology to evaluate and map the relative environmental sensitivity of lands throughout the M.D..
 
1.1 Study Area
The M.D. (Figure 1) has a wide variety of topographic features, generally increasing in elevation from east to west and, as a result, has significant climatological and biological diversity.  The area transitions from mixed grass ecoregion (Figure 2) found in the extreme southeast of the municipality, to fescue grasslands and aspen parkland, which occupy the majority of the M.D., to the mountainous regions found in the Alberta Upland on the western boundary.  The pattern of human use and development in the M.D. is a reflection of the natural diversity found across the M.D. landscape.  Agriculture still dominates land use patterns in the M.D. (Figure 3).  Cultivated croplands dominate the eastern portion of the M.D. while lands used predominantly for grazing and forage occupy the western half.  Much of the native cover of the M.D. has been converted to croplands, forage or tame pasture.  This land use pattern is rapidly changing.  The proximity to Calgary has brought increased pressures for country residential development and recreation opportunities to the northern half of the M.D..

Figure 1:  M.D. of Foothills


 
 
 
 
 

Figure 2:  Ecoregions in the MD of Foothills


Figure 3:  Landcover in the MD of Foothills

The vegetation communities within the Ecoregions include three primary types of grassland communities, ranging from the rough fescue-sedge communities of the Western Alberta Uplands to parry oatgrass-rough fescue communities of the Foothills Fescue grassland Ecoregion.  Plant species more commonly associated with the needle and thread-blue gramma grass - wheat grass communities of the Mixedgrass Prairie Ecoregion can also be found well into the central part of the M.D. on suitable sites.  Forest cover in the M.D. is also diverse with lodgepole pine-white spruce dominating undisturbed sites in the western portion of the M.D. and giving way to limited aspen-balsam poplar communities in the central and eastern portions of the M.D..  Willow and birch shrublands also make up a considerable portion of the native plant cover in the western and central portions of the M.D..

2.0 Background

There has been considerable work at the provincial scale to identify environmentally-significant areas (http://www.cd.gov.ab.ca/preserving/parks/anhic/esa.asp) in the province.  These areas are based on their representativeness, diversity, naturalness and ecological integrity.  This work has resulted in the identification of areas at a provincial, national, and international scale within the province.  Designation at this scale is of limited use for management and protection of natural resources and ecosystem processes at the scale of the M.D..  This project refines the environmentally significant areas evaluation process to identify environmentally-sensitive areas at a scale useful for planning for the M.D..

For the purposes of this study, environmentally sensitive areas (ESA's) include key physical ecosystem components and complexes that are vulnerable to the potential impacts of a broad range of land use, development and management activities, particularly, the alteration, disruption or destruction of fish and wildlife habitat, permanent or temporary soil disturbance, the removal or modification of native vegetation cover, or the release of biological or chemical contaminants.  Environmentally-sensitive areas also include ecosystem or landscape elements where the impacts of land use, development or management activities as described above may directly or indirectly affect ecosystem areas or features.

Despite a number of individual studies to identify candidate environmentally-significant areas the biophysical and climatic variation found within the M.D. remains under-represented by proposed environmentally-significant models.  Past work related to the designation of protected spaces or environmentally-significant areas in the M.D. has resulted in a series of proposed areas primarily concentrated along the western boundary of the M.D.  These areas have also been identified for portions of the Sheep, Highwood and Bow Rivers and for a portion of Pekisko Creek.  Other small areas in the central and eastern portions of the M.D. have been identified as environmentally-significant areas including Frank Lake and the Okotoks Erratic.  Generally however, the grasslands and boreal forest ecoregions, and their associated wildlife and plant populations are poorly represented in past environmentally-significant areas studies.  In addition, past studies have not considered environmentally-significant  areas in the context of a larger connected reserve network, in terms of habitat fragmentation or patch size.

3.0 Methods

This project identifies environmentally sensitive area within the M.D. of Foothills based on the evaluation of limited spatial data, such as groundwater, surface water and terrestrial ecosystem components.  Natural resource and cultural data were collected to provide the baseline information for evaluation.  Sensitive environmental features and sensitive zones surrounding those features were identified based on professional judgment and reviews of related literature and existing information.  The relative sensitivity of any given land location within the M.D. was evaluated by ranking each feature and sensitive zone using a simple numerical index (Table 1).  Sensitive features were then overlaid with each other using a GIS.  The relative sensitivity of a given area was established by simply calculating the sum of total index values of the overlapping sensitive features occupying any given area.
 

Table 1:  Environmental Sensitivity Ranking Criteria
 
Variable
Rank
Description
Aquifer Vulnerability
1
Low
2
Medium
3
High
4
Very high
BSOD
4
All Locations
Landcover
4
Trees
4
Grassland
4
Shrubs
1
Forage
1
Cropland
1
Other Lands
Roadless Lands
1
0-300m from nearest road
2
>300-700m
3
>700-1000m
4
>1000m
Parks and Protected Areas
2
500m buffer
4
Inside Administrative boundaries
Riparian Sensitive Zones
30m
100m
200m
2
2
1
Provincial Code of Practice Class D
3
2
1
Provincial Code of Practice Class C
4
3
2
Provincial Code of Practice Class B
4
4
3
Provincial Code of Practice Class A
4
Lakes-Ponds-Wetlands

Numerically higher values indicated more potential sensitivity
 
 
 

3.1 Groundwater Sensitivity Analysis

The groundwater sensitivity analysis for this project does not deal with the issues of groundwater sourcing, groundwater allocation, or aquifer depletion.  While these are important and legitimate issues with respect to development plans and approvals, for the purpose of an environmentally-sensitive lands evaluation they are excluded because this type of information does not exist for the M.D.  Identification of aquifers at risk of depletion is a time and money-intensive task requiring considerable fieldwork beyond the scope of this project.  Groundwater withdrawal is controlled and licensed by the Government of Alberta and as such, decisions with regard to allocation are beyond the direct control of the M.D.  For the purpose of identifying environmentally sensitive areas, this evaluation considers groundwater sensitivity from the perspective of potential vulnerability to contamination as a result of land development or land use activities only.

For this study, the approximate regional vulnerability to contamination (Figure 4) has been estimated using surficial geology data.  Materials of coarser texture such as river-lain sands or gravels are more permeable and allow more rapid infiltration of contaminants to shallow groundwater.  These areas have a relatively higher contamination risk.  Conversely, thick lacustrine clays are relatively impermeable and pose a very low contamination risk to shallow groundwater.  Fractured glacial tills pose a moderate to low risk.


Figure 4:  Groundwater Vulnerability

These areas were ranked into one of four risk categories (Low, Medium, High or Very High) based on the assumed vertical permeability of the geological material.  Each groundwater sensitivity category was also assigned an environmental sensitivity value ranging from 1(Low) to 4(Very High).  This value was used to contribute to the calculation of overall environmental sensitivity in combination with other factors (see Section 3.3).  Areas at Very High or High vulnerability to shallow groundwater contamination may be considered to be of considerable environmental sensitivity due to potential effects on groundwater and surface water resources.

The regional-scale vulnerability information is used most appropriately to gauge the relative vulnerability of an area.  This evaluation should not be considered a definitive or quantitative evaluation of the actual risk of groundwater contamination for any given area.  However, an area may be judged to be more sensitive to contamination than another area under the same development conditions.  Actual risk for individual projects can only be determined by a site-specific investigation under the direction of a groundwater professional.

The vulnerability evaluation identifies groundwater contamination as an issue that should be specifically addressed within development proposals through alternative site selection and /or mitigation strategies and identifies the need for additional groundwater studies. The groundwater vulnerability evaluation also contributes to an understanding of regional environmental sensitivity when evaluated in concert with other intrinsically connected factors such as surface water resources and fish and aquatic wildlife habitat.

3.2 Surface Water Sensitivity Analysis
 

3.2.1 Riparian Zones
 The riparian zone, the area where vegetation type and abundance is influenced by the elevated water table and deep soils adjacent to a water body, is often identified as an environmentally sensitive zone.  Healthy riparian zones provide a number of critical ecological services, and their importance to both aquatic and terrestrial ecosystem function is critical despite the relatively small geographic area they occupy within a watershed.
 
A variety of literature was reviewed to identify methods or procedures for mapping environmentally sensitive lands surrounding surface water features (lakes, ponds, wetlands, and streams).  The review was concentrated primarily on Provincial and Federal Government Guidelines, Codes of Practice, and Standards related to petroleum, forestry, and livestock operations as well as subdivision developments.  A limited review of related scientific literature was also conducted.  Ecological and distance criteria for the designation of riparian buffer zones were identified as the primary result of the review.
 
Recommendations for application within the M.D. of Foothills were derived from the literature, from observations made in the field, from consultation with Provincial Fish and Wildlife Biologists, and through consultation with water and land management specialists from PFRA.  Recommendations from the literature can be classified into two primary categories - those approaches that rely on a specified fixed-width setback distance, and those that rely on the evaluation of site-specific ecological criteria.  Minor watercourses (intermittent streams, wetlands) should be protected with a 30 and 100 m buffer.  Larger, permanent streams and lakes should be protected with a 30, 100 and 200 m buffer (Table 1).  Each buffer zone needs a different type and level of protection and management.
 
3.3 Terrestrial Environment Sensitivity Analysis
3.3.1 Biodiversity Species Observation Database (BSOD)
The BSOD is managed by Alberta Sustainable Resource Development and provides observation data on all sensitive wildlife species or wildlife species at risk (Figure 5).  The BSOD consists of point data with location accuracy ranging from 200m to 5000m.  The time frame of the observation data ranges from long term, multiple observations of a species occupying a site over time to single one-time observations.  Some of the data was collected some time ago and may suggest wildlife use of an area that no longer occurs.  Conversely, the lack of observation data does not suggest that a given species does not occupy a particular location.
 
Despite these limitations, the BSOD is useful in that it identifies potential wildlife issues within the accuracy limits and suggests potential wildlife use of similar sites in the general area of the observation.  Multiple observations in the same location over time are likely a reasonable indication that the area serves as important habitat for sensitive species.  Observation data was buffered using the accuracy field in the database to identify the radius within which the observation occurred.
 
3.3.2 Alberta Natural History Information Centre (ANHIC) Rare Plants Database
The ANHIC Rare Plants Database (Figure 5) is similar in nature to the BSOD in that it consists of point data with limited accuracy.  As with the BSOD, the Rare Plant Database is useful in that it identifies the general locations of rare species and highlights the potential need for site-specific vegetation studies or consultation with ANHIC or Alberta Sustainable Resource Development.
 
3.3.3 Environmentally Significant Areas
Environmentally Significant Area studies pertaining to the M.D. of Foothill have been conducted several times in the past and include studies by the Calgary Regional Planning Commission and Alberta Environment.  The Environmentally Significant Areas designated through past studies were reviewed and mapped in an independent report conducted for the Environment Committee in 1998 (Figure 5).
 
While the M.D. has found that the past studies do not suit its purposes, it is worth noting that the Environmental Reference Manual for the Review of Subdivisions in Alberta (Alberta Environment 1996) specifically refers to impacts on Environmentally Significant Areas as designated by the Province.  In particular, Chapter 4(I) states "major environmental constraints to development, as well as potential adverse impacts on Environmentally Significant Areas, may be mitigated in some cases by lot redesign and site-specific environmental evaluations".  This reference suggests that development within an Environmentally Significant Areas is intended to be quite restrictive and is intended to be an exception rather than the rule.  Provincially designated Environmentally Significant Areas should be considered in accordance with the Manual and related Acts regardless of other M.D. objectives or alternative designations of environmentally significant areas.

Figure 5:  BSOD, Rare Plants, and Environmentally Significant Areas

3.3.4 Landcover/Vegetation

Information on vegetation cover and land use in the M.D. is taken from Classified Landcover database interpreted from 1995 satellite imagery (Figure 3).  The data has a 30m resolution and separates land cover into broad categories including grassland, shrubs, trees, forage and cultivated lands.  No distinction is made between native grasslands or tame pastures or for different forest cover types.   In addition to the above limitations, land uses are constantly changing; trees are cleared for pasture or development, aspen forests encroach on grasslands over time, native grasslands are replaced with tame grasses, crop types and forages are alternated or changed.  All of these limit the accuracy of the data, particularly with regard to site-specific evaluation.
 
Generally, however, the Classified Landcover provides an accurate depiction of vegetation cover and land use patterns across the M.D..  As such, it is useful for identifying broad areas that may be suitable as wildlife habitat.  Areas of forest, shrub and grassland cover are generally considered to be less disturbed than areas of forage or cultivation and to support greater levels of native biodiversity.  These areas can be considered to be the most sensitive in terms of potential impacts to wildlife and habitat.  Native grasslands are among the most endangered ecosystems on the prairies and most wildlife species in the M.D. that are listed as "at risk" or "sensitive" by Alberta Sustainable Resource Development are strongly associated with native grasslands.  A detailed survey of native grasslands in the M.D. would be a very valuable tool for evaluating environmental sensitivity.  This is not to suggest that lands in forage or in cultivation have no values for wildlife.  Ungulates and waterfowl in particular use these areas for feeding and nesting habitat.  However areas in forage or cultivation can be seen to be relatively less sensitive than lands that remain under native cover.  Few sensitive species or species at risk rely on cultivated or forage lands as habitat.
 
3.3.5 Parks and Protected Areas
Parks and Protected Areas managed by Alberta Sustainable Resource Development, Alberta Community Development, Heritage Canada or non-government organizations were mapped as sensitive areas.  There are very few protected areas in the M.D. the largest being the 1942ha Ann and Sandy Cross Conservation Area.  These areas may serve as important core wildlife habitat or protect valued cultural or heritage features e.g., Bar U Ranch Historic Site.
Land use and land development activities immediately adjacent to protected areas may have deleterious impacts that extend well into parks and protected areas making them effectively smaller as wildlife habitat.  Impacts may include noise and visual disturbance, vandalism and accidental damage by humans e.g., fire, predation from domestic animals, colonization of invasive species, chemical contamination from herbicides or pesticides, and removal of vegetation that may reduce protective cover and increase the intensity of edge effects.  Variable width buffers utilizing zoning designations similar to those for riparian sensitive zones should be established on a case-by-case basis for all parks and protected areas in the M.D.. Parks and protected areas were buffered at a distance of 500m for the purposes of this study.
 
3.3.6 Roadless Lands
Roadless areas and other undeveloped landscapes can be expected to contain wildlife species sensitive to human activities and disturbance.  Large species such as black bear and predators such as cougars are particularly sensitive to human disturbance and require large areas to accommodate their home ranges.  Most species at risk are also sensitive to human caused disturbance or modification of natural habitats.
 
Considered in isolation, roadless or undeveloped lands do not necessarily indicate environmentally sensitive lands.  However when considered in combination with other factors such as vegetation cover and the presence of species at risk, roadless lands may indicate prime areas for the designation of protected areas or the implementation of environmental protection and conservation management measures.  For this project roadless lands were calculated and mapped based on 1:20,000 transportation data (Figure 6)

Figure 6:  Roadless Areas

3.3.7 Steep Slopes

The M.D. of Foothills specifies slope limits for the development of roads and building sites.  Roads are not to exceed a grade of greater than 7%.  Building parcels are not approved on slopes exceeding a grade of greater than 15%.  While these specifications are primarily intended for pragmatic operational, maintenance and safety purposes, steeper slopes may also be considered to have greater potential for erosion, and the transfer of sediment and contaminants downstream during runoff events is accomplished more quickly.  Disruption of vegetation on steep slopes may exacerbate these potential issues.  Steeper slopes are the least likely to have been broken for agriculture or heavily grazed and may be among the least disturbed native vegetation environments in the M.D.. Slope maps can be used to help identify areas at risk of erosion or that may affect water quality by expediting the movement of contaminants downhill or downstream.
 
Slope maps were created for the M.D. using Digital Elevation Model (DEM) data. Although maps with any slope interval can be created with the DEM, for the purposes of this project it was decided to use the specifications that the M.D. planning staff already use for evaluation of development plans; 0-7%, >7-15%, >15% (Figure 7).

Figure 7:  Slope Classification

3.4 Environmentally Sensitive Lands Analysis

The purpose of the environmentally sensitive lands analysis is to provide the Environment Committee with a way to evaluate and compare the relative environmental sensitivity of lands across the M.D..  The analysis accomplishes this task by mapping and ranking concentrations of sensitive ecological variables from the groundwater, surface water and terrestrial evaluations.

Ecological variables included the analysis are:

All map data were converted to raster format.  Each variable was assigned an environmental sensitivity value from 1 (least sensitive) to 4 (most sensitive).  Numerical scores were based on existing available rankings for aquifer vulnerability.  The remaining variables were assigned scores on the basis of professional judgments about the relative sensitivity of each feature to potential development impacts.  Environmental sensitivity values for each variable are summarized in Table 1.
 
The sensitivity values for each variable occupying any given cell were summed to yield a total score for each cell (ArcGIS 8.1 GRID).  The possible score for any given cell ranges from 0 (sites with no data) to 24 (sites where the value for every variable = 4).  The data were classified into 4 classes using the Natural Breaks default classification method in ArcView 3.2.  This method identifies breakpoints between classes using a statistical formula (Jenk's optimization).  The Natural Breaks method finds groupings and patterns inherent in the data.  The resultant map provides a graphic representation of the location, pattern and concentration of sensitive ecological variables across the M.D. (Figure 8).



Figure 8:  Environmentally Sensitive Areas Analysis

 
4.0 Conlcusion
 
This project evaluated the environmental sensitivity of lands throughout the M.D. based on analysis of groundwater, surface water and terrestrial ecological features.  The environmentally sensitive lands analysis provides the M.D.'s Environment Committee with a way to evaluate and compare the relative environmental sensitivity of lands across the M.D..  The analysis accomplishes this task by mapping and ranking concentrations of sensitive ecological variables from the groundwater, surface water and terrestrial evaluations.  Limited, existing, ecological data provided useful information to delineate environmentally sensitive areas. Project outputs provide useful planning information appropriate for identifying areas of concern, scoping environmental issues, and guiding further analysis and study.

5.0 References
 

Alberta Environment. 1996. Environmental Reference Manual for the Review of Subdivisions in Alberta. Standards and Guidelines Branch, Environmental Assessment Division, Environmental Regulatory Service. Edmonton.
 
Acknowledgements
Any opinion or conclusion expressed in this report is that of the authors of the report and should not be construed as the opinion, the conclusion or binding upon the Environment Committee, the Planning Department, the Council of the M.D. of Foothills No. 31 or the people or organizations contributing critical review.
 
This document has not been adopted by Council, the Planning Department or the Environment Committee of the M.D. of Foothills No. 31.
Author Information
Kim Hodge, Regional Land Use Analyst, Agriculture and Agri-Food Canada, Prairie Farm Rehabilitation Administration.  #600 138 4 Ave SE, Calgary, Alberta, Canada  T2G 4Z6.  ph 403.292.4562, fax 403.292.5659, email hodgek@agr.gc.ca
 
Neil Gilson, Environmental Science and Assessment Coordinator, Parks Canada Agency, Western Canada Service Centre.  550, 220 - 4th Ave S.E. Calgary, Alberta, Canada  T2G 4X3