Ministry of Environment


4.4 Soil And Terrain Surveys From 1975

T.M. Lord

The preceding sections introduce the reader to the beginnings of soil surveys in the province and carry him through the development and use of soil and terrain surveys as a base for the Canada Land Inventory (CLI) mapping program, which ended officially in British Columbia in the spring of 1975. Apart from completing the publication of land capability maps and the funding of special projects, the resource analysis was completed of a vast area comprising some 96 million ha. Coincidental with the progress of the land inventory program was an increased expertise in the mapping of soil and terrain units, refinements in technology, and a sharp rise in the volume of requests by land managers for basic resource information. These "spinoffs" from the CLI program have important ramifications for the present and future direction of soil and landform surveys in British Columbia.

Although the soil surveyor has traditionally made use of other natural sciences, he was sometimes forced, in remote, unclassified areas, to rely entirely on his own judgment in describing terrain units, plant communities and geological structures. Today he is part of a resource team that comprises specialists in hard rock geology, terrain analysis, vegetation, climate, hydrology, etc.

Upon completion of the CLI field program in 1975, a large amount of survey information was available. This included new knowledge of the soils and landforms of the province, particularly in the northern half and within the mountain ranges. Already the application of this fresh information has altered the soils picture of British Columbia as depicted on the recently published soil map. For example we now recognize a more extensive distribution of Humo-Ferric Podzols within the interior plateau, and have mapped Ferro-Humic Podzols and Folisols within the mild rainforest belt of the outer coast. Recent surveys in the mountains and through the northern plateaus have enabled us to map more accurately areas formerly labeled as "dominantly rockland".

This new information on our soils is closely related to the development of more refined systems for classifying and mapping terrain and vegetation. Although practically all resource mapping under the CLI program was done at a scale of 1:50,000, the principles involved apply equally to any scale of mapping. That is, the terrain or landform units are first identified by stereoscopic photo interpretation and then delineated on airphotos. The soils and vegetation are next described within this established framework. Reconnaissance soil surveys, covering a range of scale from about 1:30,000 to 1:125,000, differ from detailed surveys (<1:30,000) mainly in degree of intensity. That is, although each map delineation must be identified, the range of soils within a map unit will be wider and more complexes may occur under a reconnaissance survey. The value and practical use of any soil-terrain survey, at any level of intensity, depends on the composition of its mapping units and their relationship to the soil map legend. Soil mapping units must not only accommodate the natural landscape pattern of soils, they must be mappable, and they must meet the objectives of the particular survey. Although mapping units may be described at the level of soil series, complexes or associations they are defined by taxonomic classes.

Only recently have soil surveyors been forced to take a critical look at how they map soils and why they show soils on maps in certain ways. This assessment has resulted largely from a rapidly growing awareness and critical evaluation of soil information by concerned users. In British Columbia, resource managers require a wide range of basic soil and related landscape data. This information includes soil descriptions, soil classification, soil moisture regime, landform types, texture and depth of materials, and vegetation associations. Although most of these data have been included in the traditional soils report and soil map and legend, the mode of presentation has often left something to be desired.

Even though "soil is soil" whether under a wheatfield or supporting a stand of Douglas-fir trees, a mapping system used for agricultural needs would not necessarily be the same as one designed for forestry purposes. Soil surveys of rugged forested terrain, carried out primarily to provide a range of soil interpretations for forestry and engineering, are of recent origin in British Columbia. They grew out of the need for soil and landform information to provide a sound base for making land capability ratings under the CLI program. Even while the soil maps were in the early stages of drafting, land managers, particularly those in private and government sectors of forest management, requested the use of this provisional soils information. It is now our task in this post-CLI period to explore some of the ways in which present and future surveys may best meet these needs.

Even while there were strong pressures from some resource managers for the basic soil and landform information in CLI maps, there was a growing awareness that these broadly-based maps did not always meet the needs of the user. With the rapid opening up of new areas to the traveling public, the importance of good resource management has become obvious. The effects of poor soil management practices that result in the scarring of a mountain side, the fouling of a stream, the loss of a new generation of trees, or the bulldozing of a grassland range are not readily hidden from view. The managers of our resources are actively trying to prevent such losses in productivity and to avoid confrontation with public pressure groups. Public and private agencies engaged in soil and terrain mapping must provide not only the basic map information but must show how to interpret clearly the survey data for any resource use.

Before getting into the uncertain area of prophecy a brief review of the present relationship of soil and terrain surveys to the natural resources of the province is in order. Soil and terrain mapping is now being done not only by federal and provincial agencies but also, and to an increasing extent, by surveyors in some of the larger forest companies. The current trend in surveys of forest land is to map at a number of levels within the detailed intensity range i.e. at scales of 1:30,000 or larger. But even if a mature forest stand growing on a steep mountain slope were mapped at the same intensity of survey as a cleared tract of level alluvial bottomland, say 1:15,000, the resulting soil and terrain information would be markedly different. Accurate photo interpretation of terrain and surficial materials, viewed through a dense tree cover, is extremely difficult even at high levels of intensity. The validity of many map unit boundaries and the components of each mapping unit must be closely field checked if dependable soil maps are to result. Soil maps produced at reconnaissance scales of 1:30,000, or smaller have limited use for forest land managers at an operational scale. Mapping units must be defined at a more detailed level for interpretive use by foresters and engineers.

The current review of present and projected developments in resource surveys is timely for a number of reasons. An important aspect of the CLI program was the introduction of new or revised classification systems for three of the basic resources - soils, landforms, and vegetation. The year 1976 saw a major revision in the Canadian System of Soil Classification (to be published 1978) under the Canada Soil Survey Committee aided by pedologists from across Canada. Some of the more important changes were: the addition of a new category - Cryosolic Order, the revision of definitions in the Brunisolic and Podzolic orders, a reduction in the number of subgroups, and the use of a more readable style and format. Included in the revised publication is a chapter on landform classification. This system is closely related to the provincial scheme of terrain classification and was developed jointly by pedologists and surficial geologists. A great deal of progress has been made by plant ecologists and botanists in devising compatible means of mapping plant communities and associations.

There have been advances in the use of Landsat remote sensing imagery and the development of the orthophoto. These and other mapping aids, including the helicopter, are helping to speed up field mapping. Computer technology in the form of data banks for the storage, analysis and display of soils information will permit more uniform classification and correlation of soil units within and between surveys.

Permanent retention and ease of recovering field data for new interpretations will enable response to questions unanswerable at present. Further, the ability to correlate statistically data for soils, terrain, climate, vegetation and water, should enhance and support land management and planning decisions.

The development of autocartography should speed up the production of flexible soil interpretation maps tailored to the specific needs of users.

By 1976 it was clear that the traditional reconnaissance soil survey had evolved into, and become part of a broad land resource program. Such programs are drawn up to meet specific objectives within a rigid time frame. The soil surveyor and terrain specialist provide field data at whatever levels of intensity are required to meet the needs of the study.

Detailed mapping of soils and landforms may be required to locate townsites and communication routes through corridors while less intensive surveys may meet the needs in the plateau and mountain sections. The pedologists and surficial geologists will be responsible for interpreting the basic resource data such as airphotos, geological and old soil reports and land surveys. Preliminary field legends will be drawn up. The format of the mapping units will be established prior to field survey. During the preliminary stages and throughout the field program, the supervisory soil and landform specialists work closely with representatives of other sectors, such as vegetation, climate, wildlife and recreation. The duties of the soil and landform specialists involve correlation of the soil and terrain mapping program, classification and sampling of soil units, and revisions in the map legend to deal with new information.

Interpretations of soil mapping units for selected uses are an integral and important part of any modern soil survey report. A rating system is generally used expressing relative degrees of risk or limitations for potential uses. A knowledge of soil behavior based on field observations and generally a limited amount of analytical data, form the basis for most suitability ratings. Although interpretations cover a wide range of uses such as recreational parks, or assessment for septic tank fields, interpretations for forestry are of major importance in British Columbia. Foresters in particular are concerned with the stability of forestry roads and how they relate to soil characteristics, bedrock geology, soil water, and forest productivity.

We can expect the new technology that is rapidly developing for computer-assisted resource planning to have far reaching effects on forest management (for example in the folio system of the British Columbia Forest Service and in similar programs in other agencies). With the development and use of federal (CanSIS) and provincial data banks there will be greater opportunities for exchanging soil information and maintaining standards for surveys by private companies and public agencies. Programs that deal with materials for highways cut and fill and topsoil criteria, could be adapted for mine reclamation. Much more than in the past, survey data must be linked to fertility and productivity analysis for agriculture and for other resources.