SHRP-H-381 Design Guidelines for the Control of Blowing and Drifting Snow Ronald D. Tabler Tabler& Associates 7505 Estate Circle Longmont, CO 80503 Strategic Highway Research Program National Research Council Washington, DC 1994 SHRP-H-381 Contract H-206 ISBN: 0-309-05758-2 Product No.: 3025 Program Manager: Don M. Harriott Project Manager: L. David Minsk Program Area Secretary: Carina S. Hreib Copyeditor: Katharyn L. Bine Production Editor: Michael Jahr February 1994 key words: blowing snow drifting snow highway maintenance road design snowdrifts snow fences snow control wind Strategic Highway Research Program National Research Council 2101 Constitution Avenue N.W. Washington, DC 20418 (202) 334-3774 The National Academy of Sciences, the American Association of State Highway and Transportation Officials, its member states, and the United States Government have an irrevocable, royalty-free, non-exclusive license throughout the world to reproduce, disseminate, publish, sell, prepare derivative works or otherwise utilize, including the right to authorize others to do so, all portions of this work first produced in conjunction with the Strategic Highway Research Program. The research, which is the subject of this publication, was funded in part by the Strategic Highway Research Program, National Research Council. The publication of this report does not necessarily indicate approval or endorsement of the findings, opinions, conclusions, or recommendations either inferred or specifically expressed herein by the National Academy of Sciences, the United States Government, or the American Association of State Highway and Transportation Officials or its member states. © 1994 Ronald D. Tabler. All rights reserved. (303) 652-3921 I.SM/NAP/294 Acknowledgments The research described herein was supported by the Strategic Highway Research Program (SHRP). SHRP is a unit of the National Research Council that was authorized by section 128 of the Surface Transportation and Uniform Relocation Assistance Act of 1987. This book was prepared in association with the University of Wyoming as prime contractor for the Strategic Highway Research Program (SHRP) contract H-206. Research leading to the new guidelines presented here was also supported by the Tensar Corporation, and by the Rocky Mountain Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture, where the author was employed for 27 years. In addition to financially supporting much of the research on drift control over the last 23 years, the Wyoming Department of Transportation has played a key role by testing most of the guidelines presented here. The author is indebted to Robert L. "Snowman" Jairell for 30 years of superlative technical support; to Dr. R. A. Schmidt for his invaluable scientific contributions, ideas, and encouragement; and to Dr. Masao Takeuchi and the Civil Engineering Research Institute, Hokkaido Development Bureau, for the opportunity to learn about snow control technology in Japan. Thanks are due Dr. Kynric Pell, Head of the Department of Mechanical Engineering, University of Wyoming, for asking the author to participate in the SHRP research project. Robert H. Hamre provided many helpful suggestions that greatly improved organization of this material, and Katharyn Bine contributed outstanding editorial assistance. Reviewers contributing helpful comments and suggestions included Donald A. Carlson, Kenneth H. Fink, John O. Hibbs, Howard A. Jongedyk, Charles Lee, John J. Pettit, Keith Rounds, Robert Samuelson, Harry Siedentopf, and Lawrence A. Staron. For further information on the U-clips (page 85) and on general snow control, contact: Ronald D. Tabler, principal, Tabler & Associates, 7505 Estate Circle, Longmont, CO 80503. The Snow Fence Guide (SHRP-H- 320) and a 21-minute video, "Effective Snow Fences" (Tape 2), are available from the Transportation Research Board, Box 289, Washington, D.C. 20055; telephone (202) 334-3214; fax (202) 334-2519. in Contents Acknowledgements ........................................... iii 1. Executive Summary ......................................... 1 1.1 Who Should Read This Book? ................................ 1 1.2 Content and Organization ................................... 2 1.3 References ............................................ 3 2. Effectiveness of Measures to Control Blowing Snow ...................... 5 2.1 Highlights ............................................ 5 2.2 The Importance of Drift Control ............................... 6 2.3 Why Drift Control Has Been Overlooked ......................... 6 2.3.1 Historical Use of Snow Fences ............................ 6 2.3.2 Why the Use of Drift Control Measures Declined ................. 9 2.4 A Case Study in Wyoming .................................. 9 2.5 Other Examples ........................................ 19 2.6 Benefits from Snow Fences ................................. 22 2.7 Benefits from Road Design ................................. 24 2.8 Conclusion ........................................... 24 2.9 References ........................................... 24 3. How Snow Moves and Forms Drifts .............................. 27 3.1 Scope .............................................. 27 3.2 Highlights ........................................... 27 3.3 Snow Particle Characteristics ................................ 29 3.4 Snow Transport ........................................ 30 3.4.1 Definition ........................................ 30 3.4.2 Modes of Snow Transport .............................. 30 3.4.3 Wind Profile .......................................... 36 3.4.4 Snow Transport Rate and Vertical Distribution .................. 37 3.4.5 Visibility in Blowing Snow .............................. 40 3.4.6 Evaporation of Blowing Snow ............................ 43 3.4.7 Snow Transport Versus Fetch and Relocated Snow ............... 49 3.4.8 Snow Surface Features ................................ 52 3.5 Snow Erosion and Deposition Processes ......................... 55 3.5.1 Erosion .......................................... 55 3.5.2 Depostion ........................................ 55 3.5.3 Inter-Particle Bonding ................................. 56 3.5.4 Snow Densification .................................. 57 3.6 Snow Deposition and Retention Due to Vegetation ................... 58 3.7 Deposition in Topographic Depressions and Road Cuts ................ 60 3.7.1 How Drifts Grow ................................... 60 3.7.2 Equilibrium Slope ................................... 62 3.7.3 Trapping Efficiency .................................. 62 3.8 Deposition at Snow Fences ................................. 64 3.8.1 Fence Height, Porosity, and Bottom Gap Defined ................ 64 3.8.2 Effect of Porous Fences on Wind and Blowing Snow Particles ........ 64 3.8.3 Stages of Drift Growth at Porous Fences ..................... 67 3.8.4 Drift Growth at Solid Fences ............................ 75 3.8.5 Equilibrium Drifts ................................... 77 3.8.5.1 Importance .................................... 77 3.8.5.2 Factors that Affect the Shape of Equilibrium Drifts ........... 77 3.8.5.2.1 Fence Height ............................... 79 3.8.5.2.2 Fence Length and End Effect ..................... 83 3.8.5.2.3 Bottom Gap ................................ 89 3.8.5.2.4 Fence Porosity .............................. 91 3.8.5.2.5 Inclination Angle ............................. 96 3.8.5.2.6 Wind Direction .............................. 96 3.8.5.2.7 Wind Speed ................................ 98 3.8.5.2.8 Effect of Topography .......................... 98 3.8.5.3 Equilibrium Drifts Formed by Various Fence Types .......... 102 3.8.6 Trapping Efficiency of Porous Fences ...................... 107 3.8.6.1 Definitions ................................... 107 3.8.6.2 Trapping Efficiency in Relation to Fence Height and Wind Speed.. 107 3.8.6.3 Other Factors that Affect Trapping Efficiency .............. 110 3.8.6.4 How Trapping Efficiency Changes with Time .............. 112 3.9 References .......................................... 116 4. Quantifying the Blowing Snow Problem ........................... 121 4.1 Scope ............................................. 121 4.2 Highlights .......................................... 121 4.3 Identifying the Problem .................................. 122 4.4 Analyzing the Problem ................................... 122 4.4.1 Problem Components ................................ 122 4.4.2 Specifying the Problem and Effects ........................ 123 4.4.3 Source of Blowing Snow .............................. 123 4.4.4 Problem Causes ................................... 124 4.5 Identifying Possible Solutions ............................... 126 4.6 Assembling Data and Information ............................ 126 4.6.1 Winter Field Measurements and Observations ................. 126 4.6.1.1 Determining Exact Location ......................... 126 4.6.1.2 Quantifying and Documenting the Drift Problem ............ 127 4.6.1.3 Measuring Prevailing Transport Direction ................ 127 4.6.1.3.1 Field Wind Measurements ...................... 127 4.6.1.3.2 Field Snowdrift Measurements .................... 128 vi 4.6.1.3.3 Other Indicators of Snow Transport Direction .......... 129 4.6.1.4 Measuring Snow Depth over the Fetch .................. 130 4.6.2 Obtaining Aerial Photographs ........................... 130 4.6.3 Assembling Climatological Data .......................... 132 4.6.3.1 Sources of Climatological