Understanding the risk of unpaved roads on drinking water treatability by assessing sediment erosion across Canada

• Author / Creator

  Hall, Jennifer

• Forest harvesting, wildfire suppression, energy resource exploration, and recreation all require
  unpaved roads. As a result, many roads in drinking watersheds are potential sources of fine (<63
  µm) sediment. Erosion of fine sediment threatens drinking water treatability as can be a source
  of increased nutrients and sediment, creating issues in reservoirs and treatment infrastructure.
  However, there is a lack of research regarding sediment yields and erosion models on unpaved
  roads in Canada. The objectives of this study were 1) to understand the variability and
  predominant factors that contribute to increased road erosion risk in Canadian drinking
  watersheds, 2) evaluate the Forest and Range Evaluation Program (FREP) used to categorize
  risk, 3) evaluate erosion and runoff dynamics from representative unpaved roads and trails within
  the Ghost and Elbow River Watershed, near Calgary, Alberta, and 4) to validate the runoff and
  sediment production predictions of the Road Erosion and Delivery Index (READI) model using
  UAV data and rainfall simulations on the representative road segments.
  The first two objectives were addressed in chapter 2 with 107 site surveys and 22 small-plot
  (1.5m 2 ) rainfall simulations. Unpaved road erosion risk was influenced by road surface
  conditions, road slope, and traffic. Furthermore, traffic and poor road surface conditions
  increased fine sediment yields. Risk was found to be highest in the Montane Cordillera which
  had poor road surfacing conditions, steep slopes, and high traffic. Rainfall simulations and the
  FREP model could not be directly compared because of sediment yield units, but when plot
  sediment yields were ranked from lest to highest sediment there was a positive linear
  relationship.
  The final 2 objectives were addressed in chapter 3 with 6 site surveys, 6 large (60-150m 2 ) and
  small rainfall (1.5m 2 ) simulations, and 5 UAV flights. Site surveys gave insight to road

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  construction, road sweep samples provided details on available sediment, runoff and erosion
  rates were assessed from the rainfall simulations, and UAV flights produced digital surface
  models that gave an understanding to road roughness. Rainfall simulations showed that large and
  small plots preferentially (>70%) eroded fine particles. The rainfall simulations erosion rates
  followed three patterns: a steady-state of erosion, an increasing rate of erosion, and a decreasing
  rate of erosion. Similarly, runoff followed three patterns; a gradual increase to a steady state,
  increase with no steady state, and a steady state throughout the simulation. Runoff started at
  different time intervals based on scale; large-scale experiments started between 8-16 minutes and
  small simulations started between 2-4 minutes. Lastly, the READI model did not accurately
  predict time-to-concentrations or sediment yields compared to rainfall simulations, expect when
  site specific roughness values from digital surface models and erosivity (K) values were applied.
  The assessment of road erosion is valuable for understanding the impacts of road management
  practices on water quality. In Canada, sediment yields predominantly consists of particles ≤ 63
  µm which poses a larger threat to drinking water treatability. Results showed fine sediment
  yields are related to traffic volume and road surface conditions. The Forest and Range Evaluation
  Program (FREP) and Road Erosion and Drainage Index (READI) models are tools to understand
  road erosion risk. These models assist in assessing sediment yields, providing useful insights for
  road managers. The appropriate method depends on the objectives and the available information
  to effectively address road erosion challenges.

• Subjects / Keywords

  • Unpaved roads
  • Drinking water treatability
  • Road erosion
  • Sediment

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-56et-5q89

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.