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Terain stability assessment using logistic regression analysis for the Jamieson-Orchid-Elbow Creeks subdrainage, Seymour River Basin, British Columbia

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Title: Terain stability assessment using logistic regression analysis for the Jamieson-Orchid-Elbow Creeks subdrainage, Seymour River Basin, British Columbia
Author: Gulyás, Gyula
Degree: Master of Science - MSc
Program: Forestry
Copyright Date: 1995
Issue Date: 2009-01-20
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]
Abstract: The purpose of this research project was to develop a procedure for terrain stability assessment by applying case-control sampling and multiple logistic regression analysis, widely used statistical techniques in biomedical research and in epidemiology. The idea of applying statistical methods used in epidemiology to terrain stability assessment was based on the observation that landslides, like some diseases, are rare phenomena. The implementation of a terrain stability assessment based on these statistical techniques was expected to help understand the causeeffect relationships between landsliding and various terrain attributes. In contrast to the currently used approaches, the study procedure provided a quantitative tool to assess the risk of landsliding and to define the most important terrain attributes that contribute to soil mass movements. A case-control study of 20x20 m grid cells with average slope greater than 10 degrees was conducted on the Jamieson-Orchid-Elbow Creeks subdrainage of the Seymour River Basin, British Columbia. All of the 101 landslide cases were compared with 264 control grid cells. Multi-way cross classification tables were constructed to study the relationship between landsliding and several terrain attributes. A possible interaction between slope angle and the drainage condition of the soil was detected. A logistic regression analysis was then performed within a Geographic Information System (GIS) environment to develop a landslide risk model for the Jamieson-Orchid-Elbow Creeks study area. A landslide risk matrix was then constructed based on the landslide risk model. It was found that sites located in the transient snow zone, with slope angle greater than 55 degrees, on bedrock outcrop surficial material type and on shallow soil have the greatest risk of experiencing rapid, shallow soil mass movements. It was also found that holding all the other variables constant, slope angle had the greatest effect on the magnitude of landslide risk. Based on the data, sites with very steep slopes (over 55 degrees) have, on the average, five times the chance of experiencing a landslide event relative to sites with gentle slopes (10-25 degrees). The landslide risk matrix was used to create landslide risk categories. The spatial distribution of landslide risk, categorized as very low, low, moderate, high and very high, is portrayed within 20-m square grid cells on the landslide risk map. The major advantage of using the landslide risk assessment of this study is that it provides the terrain mapper with quantitative information about the relative risk of landsliding. This information can be used as a tool in planning watershed management activities and in an overall risk assessment for a given geographic area.
Affiliation: Forestry, Faculty of
URI: http://hdl.handle.net/2429/3807
Scholarly Level: Graduate

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