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Classification and detailed mapping of soil and terrain features in two mountainous watersheds of southeastern British Columbia

University of British Columbia

This study was undertaken to investigate detailed land classification in forested mountainous terrain. Two small watersheds in south-eastern British Columbia, each of approximately 3500 ha in area, were selected for classification and mapping of terrain and soil features (a simultaneous study completed vegetation classification and mapping). The results of the study include maps of terrain and soil features presented on photo-maps at scales of approximately 1:8,000 and planimetric maps at scales of 1:15,840; written descriptions of the terrain and soil features; cross-sectional diagrams depicting the relationships between various landscape features; and soil interpretations for erosion and forest capability. The terrain features are classified primarily on the basis of genesis and secondary characteristics of surface expression, texture, slope, and modifying processes. The soils were classified as phases of soil families according to the Canadian System of Soil Classification. The Templeton River study area, located in the Purcell Mountains and the adjacent Rocky Mountain Trench, has a complex array of terrain features derived from sedimentary rocks. These include a variety of morainal materials ranging from rubbly materials associated with presently active ice to compact fine textured non-calcareous and moderately textured calcareous materials. Steep slopes have created abundant colluvial features including aprons and fans which grade to shallow colluvial veneers over bedrock or morainal materials. The valley mouth has abundant glaciofluvial and glaciolacustrine features, with minor areas of fluvial materials adjacent to Templeton River. The soils of the area are highly variable, reflecting complex variation in parent materials, climate, and vegetation. At the lower elevations the soils are dominantly Luvisols, which grade to Brunisols and Podzols in the cooler and moister environments. The Grassy Creek study area, located in the Selkirk Mountains, is dominated by morainal materials of relatively uniform composition. These materials are moderately coarse textured and derived from granitic bedrock. There are fluvial and glaciofluvial materials in the valley bottom and limited colluvial materials at the upper elevations, primarily on southern aspects. The soils are acidic Podzols, with Ferro-Humic Podzols in the poorly drained areas, Humo-Ferric Podzols in better drained areas, and some Brunisols on rapidly drained sites. A systematic sampling study in the Templeton River study area demonstrated that mapping reliability for the terrain units was about 80%, and for the soil units about 65%. Morainal mapping units were more homogeneous and had higher mapping reliability than glaciofluvial mapping units. A comparison between the more detailed mapping completed in this study and reconnaissance terrain and soil mapping completed previously in the study areas identified a number of problems inherent in inventories which rely on interpretation of aerial photographs with limited ground checking. The complex interactions between terrain types, relief, and vegetation patterns of Templeton River limited the utility of reconnaissance aerial photographic interpretation. In contrast, Grassy Creek, with subdued and more uniform terrain features showed good agreement between detailed and reconnaissance mapping.

Text

2010-03-02

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http://hdl.handle.net/2429/21297

Soil Science

University of British Columbia

Graduate