Document type: DU ETD
Collection: Geology Theses  
Title Mass Movements Resulting From Intense Rainfall, Douglas County, Colorado: A Morphometric Analysis
Author(s) Kuhaida Jr., Andrew Jerome
School/Department Department of Geography
Institution University of Denver
Degree Type Doctoral
Degree Name Ph.D.
Type of Resource text
Degree Date 1980 May
Digital Origin reformatted digital
Rights Statement All Rights Reserved
Reason for Restrictions No restrictions
Type of Restriction No restrictions
Keyword(s) Geography
Abstract On June 16, 1965, intense rainfall triggered numerous mass movements in Douglas County, Colorado.The purpose of this study was to examine these mass movements and determine the:(1) spatial distribution, (2) specific form and type, (3) contributing environmental factors, and (4) potential hazardous areas.Geometric and environmental field measurements were made on 45 scars.Geometric form measurements were used as the basis for the development of morphometric indices. The indices used were:depth (head)/length, depth (head)/width (source area), width (source area)/ length (source area), depth (head)/depth (side), depth (head)/total length of scar, length (source area)/total length of scar, width of transport zone/width (source area), shape, and volume.Correlation analysis was used to identify relations among the morphometric indices. Cluster analysis was used to identify groups of scars with similar morphometric characteristics. Each group of scars was then examined to identify environmental factors and hazard potential.Results of correlation analysis indicated two statistically significant relationships. Negative correlations exist between: (1) L/Lt and wc/W, and (2) D/Lt and wc/W. Both of these relationships suggest an association between the morphometry of the scars and the flow characteristics of the moving mass. In effect, channelization is related to both the displacement and volume of material from the source area. A long, narrow scar is produced by a moving viscous mass following existing drainageways downslope. With cluster analysis, four groups of scars were obtained that share similar morphometric characteristics. Group 1 was characterized by high L/Lt index values which suggested that sliding was the initial type of movement from the source area.Group 2 contained only one scar and was subsequently excluded from further analysis. Group 3 included scars with low values for the D/Lt index, suggesting that flowage was the operating process as material moved from the source area. Group 4 was comprised of scars exhibiting high values for the D/Ds index.This suggests rotational movement (slumping) of material within the source area. With each group, the material was apparently transformed into a flow as it moved through the transport zone. Environmental factors examined included topography, surface materials, and vegetation. A majority of the 45 scars were located on slopes with a northwest to northeast orientation. The only two associations observed between surface materials and types of movement occurred with groups 1 and 4. The scars in group 1 (slides) had a shear surface of gravelly-sand underlain by a distinct clay layer. Sixty percent of the scars in group 4 (slumps) occurred in surficial material thicker than five feet. No association between vegetation type or ground cover was observed.A hierarchy of hazardous areas for this type of mass movements was recognized.All areas beneath mesas and buttes possess some hazard, including the gently inclined areas at the base of the slopes. The next most hazardous locations include areas adjacent to drainage-ways at the base of slopes.At such locations, the greater the relief between the slope base and upland surfaces, the more extensive is the potentially affected area.The most hazardous situation occurs in those areas near the base of a north-facing slope and adjacent to drainageways.From this study, it can be concluded that a morphometric examination of mass movements has significant potential as a method of analyses for mass movements. Types of movement, factors contributing to movement and potentially affected areas can be suggested. However, more work is needed with various types of movements and in other locations before the full potential can be established.
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Created: Mon, 25 Oct 2010, 10:35:54 UTC by John Adams . Detailed History