The Importance of Severe Weather Monitoring

In recent years, extreme weather events have been major contributing factors to several pipeline failures. The Pipeline and Hazardous Materials Safety Administration (PHMSA) defines extreme, or severe, weather as any event that has the likelihood of damaging pipeline facilities (49 CFR § 192.613 and §195.414). Severe weather events include tropical cyclones, such as typhoons, tropical storms, or hurricanes. Along coastlines, storm surges are considered one of the deadliest and most destructive hazards associated with tropical cyclones. A storm surge is an abnormal rise of water generated by intense storms, over and above normal sea level (i.e., predicted astronomical tide); they commonly result in extreme coastal and inland flooding.

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Storm surges are complex events which are influenced by a variety of storm factors: wind intensity, pressure levels, size, speed, angle of approach to the coast, and the shape of the coastline. These factors all interplay to generate surges of differing magnitudes. The most influential factors in storm surge generation and coastal impact are wind intensity (speed) and pressure levels. In general, low storm pressure and high wind speeds create greater storm surge potential.

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Land surface elevation and local topographic features directly influence storm surge behavior and the risk of flooding. Coastal areas where the land surface lies less than ~ 10 feet above sea level are at particular risk for flooding. For example, storm surge traveled upwards of 30 miles inland in southeastern Texas and southwestern Louisiana during Hurricane Ike in 2008. In comparison, historic storm surge events on the west coast of Oregon only travel 1 to 2 miles inland due to the high land surface elevation and complex topography. Local topographic features (e.g., buildings, levees, sand dunes, mountainous terrain) generally reduce storm surge forces and flooding.

Model results for 1 m, 3 m, and 9 m storm surge events along coastal Texas (left) and Oregon (right). Variations in topography directly affect the extent of coastal and inland flooding.

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Heavy rainfall, dangerous wind speeds, and storm surge can severely impact the land surface and shallow subsurface (less than 10 feet) during an extreme weather event. The rise in water and increased wind speeds can create turbulent flows which cause scour and erosion, or the movement of surface material (e.g., soil and sediment). Turbulent flows often collect and deposit sediment and large debris as they move, which increases the risk of flood damage. Flooding due to storm surge can also generate other geohazards, such as landslides and stream channel erosion, migration, and/or washouts. This process is called cascading hazards, where a primary event (i.e., flooding) triggers a chain of subsequent hazards.

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Turbulent flows and cascading hazards have the potential to negatively impact pipeline integrity, causing operational disruptions, exposure, damage and/or failure. PHMSA amended 49 CFR § 192.613 (Continuing Surveillance) and §195.414 (Inspection of Pipelines in Areas Affected by Extreme Weather and Natural Disasters) which now require operators to inspect potentially damaged infrastructure within 72 hours of a severe weather occurrence. Upon detection of pipeline damage or failure, an operator must take prompt remedial action to ensure the safe operation of the pipeline and prevent environmental damage. The 72-hour window starts when the operator reasonably determines that the affected area can be safely accessed by personnel and equipment.

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REA recommends that operators incorporate severe weather inspection planning and management into their current geohazards and maintenance programs by:

 

• Identifying all high-risk sites prior to severe weather occurring,

• Allocating resources to inspect areas of highest concern promptly, and

• Having an in-place plan to inspect all potentially damaged infrastructure within 72 hours of the event using the right resources at the right time.

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A comprehensive severe weather program reduces threats to the environment and improves public safety and awareness for communities located near pipeline infrastructure.

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3D visualization of a storm surge event:

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