Ministry of Environment Terrain

Terrain Information

The geological materials that underlie the surface of the land are one of our most important resources. Surficial materials (unconsolidated deposits such as sand, gravel and glacial till: the engineer's "soil") that range in thickness from a few centimetres to several hundreds of metres overlie solid rock (bedrock) in most places. They form the parent material of the soil (in an agricultural sense) from which we harvest crops and timber. They provide the natural footing upon which bridges, highways, pipelines and transmission lines are constructed, as well as foundations for our own dwellings and most urban structures. Groundwater may be stored within certain types of surficial materials.

Characteristics of surficial materials and landforms vary greatly from place to place. Land that is susceptible to subsidence or landslides may be adjacent to stable terrain that provides good sites for construction. Steep slopes underlain by a particular type of surficial material may be prone to surface erosion should deforestation occur, but similarly steep slopes elsewhere, underlain by different material, may be much more resistant to erosion. Some areas are affected by hazardous geomorphological processes (natural hazards), such as avalanches, mudflows, and floods, that may threaten property, structures, communication lines and even human safety.

Terrain maps provide information about the distribution and characteristics of surficial materials, landforms, and geomorphological processes. The physical properties and conditions of the land surface can be assessed from these data. All of British Columbia except the highest mountain peaks was covered by glaciers several times during the past two or three million years. Most surficial materials were deposited either during the most recent glaciation which lasted from about 29000 to 10000 years ago, or since then during postglacial time. Within the four billion years of earth history, these materials are very young indeed.

An examination of the characteristics and properties of terrain is an essential step in any planning process. Appropriate use, in a physical sense, can then be made of land surface materials and optimal land management practices can be determined; natural hazards can be avoided.

This booklet has been written in order to enable land managers, planners, foresters, biologists, engineers and other non-geologists to make use of terrain map information. Its use is particularly recommended with terrain maps that are not accompanied by a regional terrain or soils report and is intended to supplement, rather than duplicate, information provided in terrain map legends. Persons reading it should keep a terrain map and legend handy for reference purposes.

Information about bedrock geology is available from the Geological Survey of Canada, 100 West Pender Street, Vancouver, British Columbia, V6B 1R8 and the Ministry of Energy, Mines and Petroleum Resources, Victoria, British Columbia, V8V 1X4.