Physical Land Classification (PLC) is a mapping system that was designed to describe
the landscape in terms of landform, soils, drainage and slope. It is a hierarchical
system that captures physiographic information at the following levels:
- Region - 1:3 000 000 or smaller
- Section - 1:1 000 000 to 1:3 000 000
- District - 1:500 000 to 1:1 000 000
- Geomorphic System - 1:100 000 (can range from 1:50 000 to 1:250 000)
- Geomorphic Unit - 1:10 000 to 1:50 000
There are some variations in this hierarchy for individual study areas.
The Land Classification Group (Resource Inventory Section), Alberta Energy and Natural
Resources, adopted the initial Physical Land Classification methodology in 1977
to meet the needs of resource planning and management agencies. Many aspects of
the methodology were developed from landform mapping schemes used by the System
of Soil Classification for Canada (1976). The PLC system is essentially a geomorphic
interpretation and classification system based on the principles of the inherent
properties of the land and its forms.
Physical Land Classification (PLC) maps have been created largely during the 1980s
and 1990s as part of a program to acquire background information for Integrated
Resource Plans along the eastern slopes and across northern Alberta. The data were
generally mapped at the geomorphic unit level using the 1:50 000 scale National
Topographic System maps as a base. The PLC hardcopy maps were scanned, georeferenced,
rectified, cleaned, vectorized, merged and attributed to form GIS polygons. The
polygons are attributed for:
- parent geologic material,
- landform / surface expression,
- modifying process,
- soil taxonomy, and
- soil drainage.
This classification system was designed to enhance and replace the Canada Land Inventory
(CLI) and Alberta Landform Inventory (ALI) Landform classification systems. There
is more attribution associated with PLC mapping than with ALI / CLI Landform mapping.
There is some overlap with the ALI / CLI Landform maps but much of the PLC mapping
was conducted in areas not covered by ALI / CLI Landform maps. PLC mapping is considered
to be more reliable than ALI / CLI Landform mapping as field checking was more extensive.
The Ram-Clearwater PLC study area (RIB# 144) covers approximately 3 500 square kilometres
in central Alberta. The study area lies within portions of the:
- Rocky Mountains,
- Rocky Mountain Foothills, and
- Western Alberta Plains Physiographic Regions.
The Rocky Mountain region is subdivided into two sub-regions:
- the Mountain Massifs, and
- the Glacially Eroded Terrain.
The Rocky Mountain Foothills is subdivided into:
- the Foothill Ridges, and
- the Mountain Outliers subregions.
The Western Alberta Plains is comprised of the:
- Burnstick Benchlands,
- the Medicine River Plain, and
- the Shunda Benchlands subregions.
The terrain is extremely variable with high relief mountains in the west, strongly
folded and faulted ridges in the foothills that lie in the central portion and rolling
to level topography in the east where the plains and benchlands are found.
The dominant material in mountainous areas is exposed bedrock. Glacial deposits
predominate in the plains and a combination of exposed rock, saprolite and glacial
materials are found in the foothills. The bedrock is largely limestone, dolomite,
shale and sandstone.
The surficial deposits include:
- glaciofluvial outwash, and
These materials are usually found in the mountain valleys and terraces as well as
within the benchlands. Ground moraine dominates and is usually associated with undulating
to strongly sloping topography.
Organic materials are found in depressions and fluvial materials are associated
with streams and rivers. Aeolian materials have developed from wind action on sand
and silt and form a very minor component of the study area. The soils are dominantly
Brunisols and Regosols in the areas of high relief. Gleysols are found in depressions
and adjacent to present day water courses. In the benchlands, the soils are dominantly
Brunisols and Luvisols with Gleysols and Organic soils in the level and depressional