State of Oregon Oregon Department of Geology and Mineral Industries Brad Avy, State Geologist INTERPRETIVE MAP 60 LANDSLIDE HAZARD AND RISK STUDY OF EUGENE-SPRINGFIELD AND LANE COUNTY, OREGON by Nancy C. Calhoun1, William J. Burns1, Jon J. Franczyk1, and Gustavo Monteverde2 2018 1Oregon Department of Geology and Mineral Industries, 800 NE Oregon Street, Suite 965, Portland, OR 97232 2Formerly with Oregon Department of Geology and Mineral Industries, 800 NE Oregon Street, Suite 965, Portland, OR 97232 Landslide Hazard and Risk Study of Eugene-Springfield and Lane County, Oregon DISCLAIMER This product is for informational purposes and may not have been prepared for or be suitable for legal, engineering, or surveying purposes. Users of this information should review or consult the primary data and information sources to ascertain the usability of the information. This publication cannot substitute for site-specific investigations by qualified practitioners. Site-specific data may give results that differ from the results shown in the publication. Cover image: Landslide inventory map of the Eugene-Springfield study area. Inset shows closeup of mapped landslides near Spencer Butte. See Plate 1 of this publication for more information. Oregon Department of Geology and Mineral Industries Interpretive Map 60 Published in conformance with ORS 516.030 For additional information: Administrative Offices 800 NE Oregon Street, Suite 965 Portland, OR 97232 Telephone 971-673-1555 https://www.oregongeology.org/ https://www.oregon.gov/DOGAMI/ Oregon Department of Geology and Mineral Industries Interpretive Map 60 ii Landslide Hazard and Risk Study of Eugene-Springfield and Lane County, Oregon CONTENTS 1.0 REPORT SUMMARY ............................................................................................................................ 1 2.0 INTRODUCTION .................................................................................................................................. 2 2.1 The Study Area ................................................................................................................................... 2 2.2 Purpose .............................................................................................................................................. 4 2.3 Adjacent Past Geologic or Related Studies ........................................................................................ 4 2.4 Engineering Geology .......................................................................................................................... 5 2.5 Landslides ......................................................................................................................................... 10 3.0 METHODS ......................................................................................................................................... 11 3.1 Landslide Hazard Evaluation Methods ............................................................................................. 13 3.1.1 Landslide inventories ............................................................................................................. 13 3.1.2 Shallow landslide susceptibility .............................................................................................. 13 3.1.3 Deep landslide susceptibility .................................................................................................. 15 3.2 Asset Data Compilation and Creation Methods ............................................................................... 18 3.2.1 Permanent population distribution dataset .......................................................................... 18 3.2.2 Buildings and land .................................................................................................................. 19 3.2.3 Critical facilities ...................................................................................................................... 20 3.2.4 Roads ...................................................................................................................................... 20 3.3 Risk Analysis Methods ...................................................................................................................... 20 3.3.1 Exposure analysis ................................................................................................................... 21 3.3.2 Hazus-MH analysis ................................................................................................................. 22 3.3.3 Annualized loss....................................................................................................................... 25 4.0 RESULTS ........................................................................................................................................... 26 4.1 Landslide Inventory Findings ............................................................................................................ 26 4.2 Shallow Landslide Susceptibility Findings ........................................................................................ 27 4.3 Deep Landslide Susceptibility Findings ............................................................................................. 29 4.4 Risk Analysis and Loss Estimation Results ........................................................................................ 29 4.4.1 Exposure analysis results ....................................................................................................... 29 4.4.2 Hazus analysis results ............................................................................................................. 31 4.5 Annualized Loss Results ................................................................................................................... 32 5.0 CONCLUSIONS, DISCUSSION, AND RECOMMENDATIONS ................................................................. 33 5.1 Awareness ........................................................................................................................................ 35 5.2 Warnings .......................................................................................................................................... 36 5.3 Development and Infrastructure Planning ....................................................................................... 36 5.4 Regulation ........................................................................................................................................ 37 5.5 Large Deep Landslide Risk Reduction ............................................................................................... 37 5.6 Emergency Response ....................................................................................................................... 38 6.0 ACKNOWLEDGMENTS ...................................................................................................................... 38 7.0 REFERENCES ..................................................................................................................................... 38 8.0 APPENDICES ..................................................................................................................................... 42 Oregon Department of Geology and Mineral Industries Interpretive Map 60 iii Landslide Hazard and Risk Study of Eugene-Springfield and Lane County, Oregon LIST OF FIGURES Figure 2-1. Map of the study area .............................................................................................................................. 2 Figure 2-2. Map of risk reporting areas/communities in the study area ................................................................... 3 Figure 2-3. Southern Willamette Valley geologic map coverage ............................................................................... 5 Figure 2-4. Map of generalized bedrock engineering geology in the study area ....................................................... 7 Figure 2-5. Map of generalized surficial engineering geology in the study area ....................................................... 9 Figure 3-1. Input datasets and results ...................................................................................................................... 12 Figure 3-2. Method for determining mean runout along the southern wall of the McKenzie River valley ............. 17 Figure 3-3. Dasymetric population distribution map input data and result examples from within the City of Eugene ............................................................................................................................................... 19 Figure 3-4. Exposure examples from the study area ................................................................................................ 22 Figure 3-5. Map of the 65 census tracts used in Hazus analysis .............................................................................. 24 Figure 4-1. Map of channelized debris flow fans in the study area ......................................................................... 28 Figure 5-1. Landslide risk management diagram ..................................................................................................... 35 LIST OF TABLES Table 3-1. Summary of geotechnical material properties for primary surficial geologic engineering units ........... 14 Table 3-2. Communities for exposure reporting ....................................................................................................