An Investigation into the 2003 Van Trump Creek Debris Flow, Mt Rainier, Washington, United States of America. Katherine Helen Mary Donovan BSc Geological Hazards School of Earth and Environmental Sciences 2005 Abstract. Debris flows are the primary geological hazard from Mt Rainier. Debris flows are mixtures of rock, mud and water that have a high sediment content and move down slope under gravity. These torrents of mud, rock and water pose a considerable risk to the Mount Rainier National Park visitors, employees, and infrastructure. The following study primarily investigates the October 20th -21st 2003 Van Trump Creek debris flow. The 2003 Van Trump Creek debris flow is an archetypal low magnitude, high frequency debris flow. An understanding of this hazard leads to the development of an effective remedial scheme, thereby reducing the risk posed to the local vulnerabilities. A combination of fieldwork recordings, observations and remote sensing techniques has been used to produce hazard and risk maps for the study area. The 2003 Van Trump Creek debris flow was triggered by a small rock fall at approximately 3218m, 200m below Camp Hazard. A debris flow only requires a water content of 30 % to flow down hill, and so coupled with an above average precipitation at that time, the rock fall material quickly transformed in to a debris flow. The mass of rock, mud and water increased in volume due to a bulking process (an increase in volume by incorporating sediment from channel banks). Although the 2003 Van Trump Creek debris flow did not travel outside the National Park boundaries, previous large magnitude flow events have reached as far as the Puget Sound, approximately 70 km north west of Mt Rainier. Avoidance strategies, warning systems, and engineering methods are necessary mitigation schemes that are emplaced at Mt Rainier to reduce the risk posed by low frequency large magnitude flows The 2003 Van Trump Creek debris flow is not unique to this region and due to the frequency of these low magnitude events, this report recommends the further introduction of some simple educational mitigation schemes, such as instructual warning signs at Van Trump Creek trailhead and at Christine Falls. This report illustrates the importance of educating the local population and tourists about the dangers, the warning signals and what to do in the event of low magnitude debris flows. 2 Contents: Page: Title page. 1 Abstract. 2 Contents. 3 Acknowledgements. 7 Methodology and Objectives. 8 Logistics. 8 1: Introduction. 9 1.1: Location. 9 1.2: Geological and Tectonic setting. 10 1.3: Eruptive history. 11 2: Debris flows. 12 3: Other Geological hazards. 14 3.1: Lahar. 14 3.2: Debris Avalanches. 15 3.3: Volcanic Gases. 17 3.4: Tephra. 18 3.5: Ballistic Projectiles. 19 3.6: Pyroclastic Flows. 19 3.7: Lava Flows. 20 4: Case Study: The 2003 Van Trump Creek Debris Flow. 21 4.1: Location. 21 4.2: Previous Debris Flows at Van Trump Creek. 21 4.3: Initiation. 22 4.4: Velocity. 24 4.5: Cross sections and Discharges. 25 4.6: Volume. 25 4.7: Behaviour. 28 4.8: Characteristics Features. 30 4.81: Boulder Front. 30 4.82: Lateral Levee. 30 4.83: Ballistic Clast Projection. 31 4.84: Buoyed Boulders. 31 3 4.9: The Effect of the Debris Flow. 32 5: Hazard Assessment. 37 6: Risk Analysis. 43 6.1: Semi Quantitative Risk Analysis. 43 6.2: Risk Map. 46 7: Monitoring Debris Flow Events at Mt Rainier. 47 8: Mitigation. 49 8.1: Education for Mitigation. 49 8.2: Recommendations for further Mitigation following the 2003 Van Trump Creek Debris Flow. 51 8.3: Mitigation for high magnitude flow events at Mt Rainier. 52 8.31: Land use planning. 52 8.32: Lahar Warning system. 53 8.33: Engineering Structures. 53 9: Discussion. 54 10: Conclusion. 55 References. 56 Appendices: (All appendices are at the back of the report) 1 Geological Map of Washington State. 2 Map of Study Area. 3 Aerial Photographs of Van Trump Creek, 1996 and 2002. 4 Cross Sections of the 2003 Van Trump Creek Debris Flow. 5 Geomorphological and Geomorphographic Maps of the 2003 Van Trump Creek Deposition Fan. 6 Walman Pebble Count Technique Data Collection. 7 Van Trump Creek Hazard and Risk Maps. 8 Questionnaire Results. 4 Figures: 1a Location of Mt Rainier, U.S.A. 9 1b Map of Mt Rainier National Park. 9 2 The Tectonic Setting of Mt Rainier. 10 3 Extent of the Osceola and Electron Mudflow, and the locations of present day settlements. 15 4 Little Tahoma Peak. 17 5 Hummock produced from the Little Tahoma Peak rock avalanche. 18 6 A pyroclastic flow travelling from the crater of Mt St Helens. 19 7 A) The unnamed waterfalls and flow path; B) The “fire hosed” scar; C) Flow route over Van Trump Park. 22 8 Precipitation data for October 2003. 23 9 Precipitation data for Longmire from 1931-1978. 23 10 Velocity of the 2003 Van Trump Creek debris flow. 25 11 View from Ricksecker Point over looking the debris fan. 26 12 The main bulking and conveyance zones of the 2003 Van Trump Creek debris flow. 26 13 Walman Pebble Count technique data for the 2003 Van Trump Creek debris flow. 28 14 Lateral Levee on the 2003 Van Trump Creek debris flow deposition fan. 30 15 Gorge switch backs down stream from Christine Falls. 31 16 An example of a buoyed boulder on the 2003 Van Trump Creek debris flow deposition fan. 31 17 Christine Falls trail bridge in 2001. 32 18 A, B) Views of the steel trail bridge in early 2003 at Van Trump Creek Falls; C, D) Views of the same location in 2004. 33 19 Granite boulder deposited at the beginning of the 2003 Van Trump Creek debris flow deposition fan. 34 20 Tree trunk cut by 2003 Van Trump Creek debris flow. 35 21 Electromagnetic Resistivity data image of Mt Rainier. 38 22 Digitalised contours for the Van Trump Creek region. 40 23 Contour map after contour interpolation. 40 5 24 A) DEM of Van Trump Creek with contour overlay; B) DEM of the Van Trump Creek. 41 25 DEM with aerial photograph overlay. 42 26 Spectrogram for the 2001 Van Trump Creek debris flow. 48 27 Total recreational visitors to Mt Rainier NP from 1904-2000. 50 28 Monthly visitors to Mt Rainier NP in 2001. 50 29 Warning sign presently at Cougar Rock Campground. 51 30 Recommended sign to be placed at the trail heads of Van Trump Creek and at Christine Falls. 51 Tables: 1 Eruptive History of Mt Rainier. 11 2 Classification of flows by water content (%). 13 3 Lahar events from Mt Rainier. 16 4 Hazard score system. 43 5 Value score system. 44 6 Vulnerability score system. 45 7 Christine Falls semi-quantitative risk analysis scores. 46 Equations: 1 Velocity of a debris flow. 24 2 Risk. 43 6 Acknowledgements. This investigation was only possible with the support and guidance offered by many people. Firstly I must thank Christopher Crowley for his support on site at Mt Rainier. Secondly to Dr Kevin Scott (Hydrologist, USGS) who supervised my work in America, and who provided opportunities that otherwise would not have been available. I would like to thank Carolyn Driedger (Outreach Coordinator, USGS) and Anne Doherty (Education Program Manager, NPS) who kindly invited me to take part in the “Living with a volcano in your backyard” teacher training course, which greatly improved my knowledge of educational mitigation. I must also thank Jim Vallance (Hydrologist, USGS) for inviting me on one of his informative field trips. I would also like to express my thanks to all the National Park Service (NPS) staff for their enthusiastic support, in particular Barbara Samora (Mt Rainier National Park Resources Manager, NPS) and Paul Kennard (Mt Rainier National Park Regional Geomorphologist, NPS). Thank you to Paul for guiding me to the Van Trump Glaciers in order to locate the debris flow initiation point. Finally I would like to thank the staff of the Earth and Environmental Science department at the University of Portsmouth, especially Dr Carmen Solana and Malcolm Whitworth. 7 Methodology and Objectives. The objective of this report is to investigate a debris flow that occurred at Mt Rainier on October 20th 2003, which flowed down the Van Trump Creek, located on the south side of the volcano. The report aims to examine the consequences of the debris flow, and evaluate the related hazards, risks and the mitigation strategies emplaced at Mt Rainier. In addition, a hazard remediation scheme is recommended for the Van Trump Creek region. The fieldwork for this investigation consisted of mapping the route of the debris flow; collecting an array of data on the debris flow using an assortment methods, including the Walman Pebble Count Technique; height and width measurements of the debris fan; cross sections of the flow route; the discharge; the velocities of the debris flow; the behaviour and overall volume of material; analysis of aerial photography and recording observations over the entire study area. Logistics. Prior to undertaking this investigation many months of research was carried out in preparation for choosing a suitable study area. During this process I contacted Dr Kevin Scott who assisted me in identifying a suitable study area. The Kautz Creek was originally identified as a potential study area, yet due to the dense forest, large area and lack of trails this proposal was discarded. The 2003 Van Trump Creek debris flow had not been investigated by either USGS or NPS personnel therefore presenting an ideal study opportunity. A Scientific Research Permit was required and this was acquired prior to the fieldwork.