Restored Crossings: When and Where to Apply Stream Restoration Techniques to Protect Exposed Pipelines

Abstract

Maintenance of existing rights-of-way often involve dealing with exposed pipelines near stream crossings. Streams often shift over time. This adjustment can lead to erosion of the streambed and streambanks, exposing pipelines or other infrastructure to threats such as hydraulic pressure, buoyancy, debris collisions, or pipe vibration and fatigue. Under these conditions, managers can be faced with relocating the pipe, performing localized streambank stabilization, or employing stream restoration techniques to provide long-term protection. When localized stabilization is the preferred approach, selection of techniques is often determined by what will protect the pipeline without consideration of the stream context surrounding it. However, due to site conditions, manager preferences, and regulatory considerations, techniques from the disciplines of stream restoration and habitat enhancement can provide cost-effective alternatives to traditional hard-armoring by concrete or stone depending on the site context. Using past experience and a series of decision analysis tools, it was determined that geomorphic context should be factored as a foremost consideration when evaluating the most stable and cost effective approach to correcting exposed pipelines. One of the most critical factors in assessing the feasibility of stabilization options is the height and orientation of exposed pipes relative to the stream’s bankfull elevation.