In British Columbia, the first geological descriptions of surficial materials were made in the late nineteenth and early twentieth centuries by geologists such as G. M. Dawson and R. Daly. These early explorers, who also made considerable contributions to our knowledge of natural history and anthropology, produced the first bedrock maps of British Columbia. They did no systematic mapping of surficial materials, although some of their bedrock maps show striations and other glacial features (Jackson and Clague, 1991). The Geological Survey of Canada initiated surficial geology mapping in British Columbia in about 1915, with mapping of the Victoria, Duncan and Saanich areas by C. Clapp. Systematic mapping of surficial materials did not begin until the late 1940s, however, when Quaternary geologists such as J. Fyles, J. E Armstrong, S. Leaming, H. Nasmith and E. Halstead began to work in southwestern B.C.
Federal soil surveys began before regular surficial geology work was established, with early maps and reports appearing in the 1920s and 1930s. At first, pedological mapping was not strongly oriented toward surficial materials, but by the 1960s, pedologists with the British Columbia Department of Agriculture (later Ministry of Environment) and Environment Canada were producing "soils and landforms" maps, on which surficial materials were specifically described.
The system of surficial geology mapping from which the present terrain mapping scheme evolved was introduced to British Columbia by R. J. Fulton of the Geological Survey of Canada in the early 1970s (Boydell, 1992). Mappers trained by Fulton were hired by the Resource Analysis Branch of the B.C. Ministry of Environment. In 1975 the mapping scheme was formalized by publication of the first terrain classification manual (E.L.U.C. Secretariat, 1975).
The 1970s and early 1980s were the heyday of terrain inventory mapping. Large areas of the province were mapped at scales ranging from 1:50,000 to 1:250,000. Work by the Geological Survey of Canada continued, but most mapping was done by Quaternary geologists and pedologists of the B.C. Ministry of Environment. Many projects were undertaken at the request of other provincial Ministries and the usefulness of terrain maps for various purposes was realized. Derivative maps (e.g., for "urban suitability", "suitability for forest roads") became routine products for some types of projects, and workshops about terrain map applications were conducted by Resource Analysis Branch geologists for other government staff.
Since the early 1980s, terrain maps have been used increasingly as the basis for many kinds of land use planning, although government-funded inventory mapping has gradually declined. Terrain maps are now used extensively by the forest industry both for general planning and as the basis for the slope stability mapping that is required before logging commences. Biophysical habitat mapping, which is used for park delimitation and planning purposes by the provincial parks department, is also based on terrain mapping. Environmental impact assessment, planning for new highways and other linear developments, regional planning, assessment of geological hazards, and fish-forestry interaction programs, all depend upon terrain maps. Terrain maps are also used as a tool for mineral exploration (e.g. Meldrum and Bobrowsky, 1994).
A terrain map (Fig. 1) is a particular type of surficial (or Quaternary) map. It shows the distribution of surficial (Quaternary) deposits and related landforms on the earth's surface. However, it also provides information about present day geomorphological processes, and in this respect it differs from surficial geology maps. For example, areas affected by processes such as debris slides, shifting river channels, and wind erosion, are indicated in the terrain symbol (commonly, these processes are referred to as "geological" or "terrain" processes). in coast, surficial geology maps provide "chronostratigraphic" information, data which does not appear on terrain maps. With the exception of the legend and unit labels, all other aspects of the guideline apply equally to surficial geology mapping and maps.
Another characteristic that distinguishes terrain maps from other surficial geology maps is that a terrain map has a flexible or "open" legend. In other words, the legend does not specify the exact form of every symbol (a group of letters) that is used on the map. Instead, the letters that together comprise the symbol for a terrain polygon are selected by the mapper to denote the particular set of conditions in that polygon (Fig. 2). Specific letters are used to describe material type, texture, landform (surface expression) and processes, and a complex of two or three different kinds of materials and processes can be indicated (see Howes and Kenk, 1988). Thus, on any given map, many polygons have unique labels. By comparison, on a map with a "closed" legend, each polygon must be assigned to a predetermined category that is listed in the legend. The preference for terrain maps versus surficial geology maps has more to do with project needs and objectives than anything else.
The standard method of terrain mapping can be adapted readily for a variety of purposes. For example, "bioterrain mapping" is being used by the Wildlife Habitat Branch of the British Columbia Ministry of Environment, Lands and Parks to provide a basis for long term planning (Appendix F). This type of mapping takes into account characteristics of the landscape that are particularly important from the point of view of wildlife habitat, but not normally used as direct criteria for the delimitation of terrain polygons, such as aspect (proxy for temperature and humidity), soil drainage, and vegetation types. As a second example, terrain maps used as a basis for slope stability assessments by the British Columbia Ministry of Forests include symbols that represent soil drainage and slope gradients (see Section 10.2).
The methodology for terrain mapping is similar to that of other kinds of surficial geology mapping. Mapping is based on air photo interpretation, which in most cases is followed by ground checking.