Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Spatio-temporal analysis of large magnitude avalanches using dendrochronology(Montana State University - Bozeman, College of Letters & Science, 2020) Peitzsch, Erich Hans; Chairperson, Graduate Committee: Jordy Hendrikx; Jordy Hendrikx, Daniel K. Stahle, Gregory T. Pederson, Karl W. Birkeland and Daniel B. Fagre were co-authors of the article, 'A regional spatio-temporal analysis of large magnitude snow avalanches using tree rings' submitted to the journal 'Natural hazards and Earth systems sciences' which is contained within this dissertation.; Gregory T. Pederson, Jordy Hendrikx, Karl W. Birkeland and Daniel B. Fagre were co-authors of the article, 'Trends in regional large magnitude snow avalanche occurrence and associated climate patterns in the U.S. northern Rocky Mountains' submitted to the journal 'Journal of climate' which is contained within this dissertation.; Chelsea Martin-Mikle, Jordy Hendrikx, Gregory T. Pederson, Karl W. Birkeland and Daniel B. Fagre were co-authors of the article, 'Vegetation characterization in avalanche paths using LIDAR and satellite imagery' submitted to the journal 'Arctic, antarctic, and alpine research' which is contained within this dissertation.Snow avalanches are a natural hazard to humans and infrastructure as well as an important landscape disturbance affecting mountain ecosystems. In many mountainous regions, records of avalanche frequency and magnitude are sparse or non-existent. Inferring historic avalanche patterns to improve forecasting and understanding requires the use of dendrochronological methods. In this dissertation, we examine a regional tree-ring derived large magnitude avalanche dataset from northwest Montana in the northern Rocky Mountains, USA, to produce avalanche chronologies at three distinct scales (path, sub-region, and region), assess seasonal climate drivers of years with large magnitude avalanche occurrence on a regional scale, and characterize vegetation in select avalanche paths. By implementing a strategic spatial sampling design and collecting a large dataset of tree-ring samples, we: (1) assessed scaling in the context of a regional avalanche chronology, reconstructed avalanche chronologies for 12 avalanche paths in four subregions, and examined the effects of two methods of sampling indexing on the resultant avalanche chronology; (2) identified specific climate drivers of large magnitude avalanche years across a region and identified trends in avalanche year probability through time; and (3) tested the feasibility of using remote sensing products to quantify vegetation types in avalanche paths and characterized the vegetation composition based on return periods within specific avalanche paths. This dissertation is organized into 3 key chapters/manuscripts (Chapters 2, 3, and 4) and two supporting chapters (Chapters 1 and 5) that address the problem of assessing large magnitude avalanche frequency at various spatio-temporal scales using a tree-ring dataset. The results contribute toward a better understanding of reconstructing regional avalanche chronologies, a more accurate assessment of avalanche-climate relationships, and improved methods to characterize vegetation characteristics within avalanche path return periods. This work has applications for regions with sparse avalanche records.Item Water movement in a stratified and inclined snowpack : implications for wet slab avalanches(Montana State University - Bozeman, College of Letters & Science, 2009) Peitzsch, Erich Hans; Chairperson, Graduate Committee: Katherine J. Hansen; Karl Birkeland (co-chair)Wet snow avalanches are dangerous and can be particularly difficult to predict. The rate of change from safe snow conditions to dangerous snow conditions occurs rapidly in a wet snowpack, often in response to water production and movement. This research focused on the relationship between snow stratigraphy and water movement in an inclined snowpack. Concentrating on transitions that impede water and flow finger formation within the snowpack, dye tracer was mixed with water and applied to a stratified snowpack to observe and measure the movement of water in various snow grain types, sizes, densities, and temperatures. There were two types of layer transitions that impeded water. Water was impeded at capillary boundaries caused by fine grains over coarse grains. It was also impeded at hydraulic conductivity boundaries, such as ice layers. In layer transitions that impeded water, the grain size of the layer above was significantly smaller than the layer below. The layer above a transition that impeded water was also significantly less dense than the layer below the transition. A qualitative analysis of grain type showed that there was no relationship between grain types in the layer above or below a transition and whether they will or will not impede water. A SnowMicroPen (SMP) was used to measure changes in structural element length to identify capillary boundaries. Results from SMP measurements indicate that microstructural analysis of the snowpack aids in characterizing capillary boundaries that impede water flow. The step change, rate of change, and percent increase were significantly larger in capillary boundaries than transitions that did not impede water for the entire dataset from all 8 sessions. When all transitions were ranked according to absolute change for each profile, capillary boundaries consistently ranked in the top two of all transitions evident within each SMP profile. The amount of water needed to produce flow fingers was highly variable. There was no significant relationship between the amount of water necessary to form flow fingers and snow density, snow grain size, snow temperature, or grain type. Layer transitions that impeded vertical water movement and flow finger formation may both play a large role in wet slab avalanche formation.