An analysis of tsunami impacts to lifelines

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Horspool, N.A.; Fraser, S.A. 2016 An analysis of tsunami impacts to lifelines. Lower Hutt, N.Z.: GNS Science. GNS Science report 2016/22 vi, 87 p.

Abstract: The findings of this review highlight that all lifelines can be impacted to some level by tsunami. Furthermore, the interdependency between lifelines can compound the disruption of services. For example, power outages impact wastewater operations, telecommunications and some transportation services such as airports and trains. Having operational transportation and telecommunications networks are also critical in being able to respond and recover from tsunami impacts. Transportation networks, such as roads, bridges, and rail will likely be damaged disrupted by even small tsunami (tsunami depths ~ 1m) due to scouring and deposition of debris. Airports that are in tsunami inundation zones will be inundated, however services can be restored quickly once debris from the runway has been cleared. Wastewater and potable water networks are particularly vulnerable to tsunami at their facility buildings and pipe intake and outflow sites. Damage to building structures or electrical equipment can cause significant service disruptions, while repairs are undertaken. Furthermore, contamination of drinking water supplies or sewerage containment ponds can occur with even small amounts of intrusion of seawater from a tsunami. Less data is available regarding the susceptibility of buried pipelines to tsunami, however it appears that such infrastructure is less vulnerable to tsunami than the above facilities. Telecommunications networks will most likely be disrupted locally due to damage to buildings and electrical equipment at exchanges. Failure of cellular sites can occur at stand alone towers that are toppled by debris strikes or scouring, as well as those located on buildings that are damaged. Again, little information is available regarding the performance of buried cables in tsunami, however it appears that buried cables are less susceptible from tsunami than overhead lines. Energy networks, particularly electricity, will be impacted due to shorting of buried cables if they become exposed to the water and have pre-existing casing damage. Also, overhead lines are susceptible to failure by toppling of poles, which can be damaged by debris strikes. Petroleum and gas terminals, often located in coastal areas may suffer damage to their pipe networks and tank farms in tsunami depths of 2m or greater. A salient observation across all lifeline sectors was that often back-up services, such as generators, were often located on the ground outside of buildings, on ground floors or in basements. Such locations put this critical equipment in the direct path of even small tsunami. It is recommended that back-up generators be raised above ground level or located on at least the second floor of buildings. Furthermore, tsunami damage ‘hot spots’ were identified where multiple lifeline damage and failure can occur. Bridges are a lifeline component that are vulnerable to tsunami and often have co-location of other lifeline services, which if damaged can cause failure of these other lifeline services. Hotspots also occurred on coastal roads, where culverts or wastewater outflows run beneath roads and through sea walls. These water channels are a site of high scour, which often results in scouring of the seawall, roadway and any underground or overhead services. Identifying and increasing the resilience of these tsunami ‘hot spots’ should be a priority for lifeline operators. Information is given in the report sections on how recovery of lifelines from tsunami was carried out from other events. Further, information is given on potential mitigation actions that can be taken by lifeline organisations to lessen the likelihood of damage and service disruption from tsunami. (auth)