*Pipeline watercourse crossing assessments require river surveys, field investigations, and detailed scour analyses to accurately determine whether a pipeline may be subject to scour deeper than their depth of cover (DOC). Typical flood scour algorithms rely on discharge, median grain size, and some measure of channel cross-sectional area to determine the tractive force of water on the stream bed (note: these algorithms are only applied to non-cohesive sediments typical of fluvial systems). To better define pipeline threats at a screening level, reducing unnecessary field and analytical expenses, and focus effort on credible hazards, we developed a flood scour screening tool that uses return period discharge (Q) as the only input requirement. In order to develop the tool, we plotted the results of over 1,200 detailed scour assessments for several grain sizes (6,000 data points) completed in Ontario, Saskatchewan, Alberta, and British Columbia, in 2018 and 2019. The results clearly show the importance of channel variability and grain size, but also showed definable discharge related trends. We compared the results of the National Engineering Handbook (NEH) and the United States Bureau of Reclamation (USBR) methods (both methods use the same algorithms), developed, and provide herein, relationships that can be used to screen out scour assessments at watercourse crossings where DOC is already known, or to support and expedite field programs where DOC is being obtained. If only Q is known, then a single graph, or single equation is used for a given region. This provides the most conservative result. If both Q and median grain size are known, then the user can determine a slightly less conservative result from a series of complimentary equations. In all cases, the result uses the more conservative USBR method, originally intended for design, to fully capture the potential variability in the calculated NEH flood scour. While conservative, the tool is easy to use, and we expect it will substantially reduce the assessment effort on smaller, or less erosive streams.*


Using Results of Western Canadian Flood Scour Assessments to Provide a Simple Screening Tool for Pipeline Watercourse Crossings

Division / Sponsors: 
Pipeline Systems Division

Paper Proceedings: https://asmedigitalcollection.asme.org/IPC/IPC2020/volume/84447

IPC2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.