Chapter 5 GROUND MOVEMENT HAZARDS (LANDSLIDES, SUBSIDENCE) AND PIPELINES: AN OVERVIEW

Because of the linear and often long nature of pipeline systems, they cross varied terrain and geologic conditions susceptible to ground movement hazards, such as landslides and subsidence. Landslide and subsidence hazards can pose significant risks to pipelines, to public health and safety, and to the environment. Over time, a large number of releases/ruptures, or pipe damage can result from the effects of landslide or subsidence movement, if the effects are left unaddressed. The timely and systematic identification, mapping, characterization and threat classification of potential ground movement hazards are important and allow pipeline owners/operators to understand the nature, spatial distribution, magnitude, extent and level of activity of the hazards, as well as their potential impacts or risks to the pipeline systems. With this information, informed hazard mitigation and informed risk management and operational decisions can be implemented.

Ground movement hazards that could affect a pipeline system are the result of naturally-occurring, active geologic processes. The geologic processes occur in the absence of a pipeline system, and only become potential hazards if they affect, or potentially affect the integrity of an existing pipeline, or the routing, design and construction of a proposed pipeline. Although landslide and subsidence processes (i.e., hazards) are naturally-occurring; they can also be triggered or exacerbated by human activity or intervention.

Whether a particular pipeline is vulnerable (at risk) or is exposed to the effects of ground movement hazards depends on several factors, including:

• The location, type, nature, age, activity, rate and extent of the hazard relative to the pipeline and its orientation.

• The pipeline’s exposure to the hazard, and the likelihood of the consequences of pipeline damage or rupture if the hazard is active.

• The type, age, material, design parameters, and construction methods and practices of the pipeline, and the operational and maintenance environment, processes and procedures of the pipeline.

Development of a basic knowledge and understanding of the types, natures, and behaviors of ground movement hazards that may impact pipeline systems, in particular landslides and subsidence, is essential for pipeline owners, operators and pipeline engineers. This paper seeks to provide that basic understanding.