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http://www.infrastructure-complexity.com/content/2/1/1

Research just published by experts in the Centre for Earth Systems Engineering Research, working with Southampton University have shown how permutable infrastructure components can reduce the risks of cascading failures.

The inter-connected and complex nature of modern infrastructure systems has created a “network of networks” that, when disrupted by deliberate action, or natural hazard event, can result in cascading failure that leads to the complete fragmentation of all connected systems from the destruction of a comparatively small number of nodes.

Existing “network of networks” approaches are still in infancy and have shown limits when trying to model the robustness of real-world systems, due to simplifying assumptions regarding network interdependencies and post-attack viability.

This work challenge such assumptions and demonstrates, through simulation, how failure to represent certain infrastructure properties can lead to inappropriate, or counterproductive, network adaptation and protection strategies in many circumstances.

1. Most assessments to date have assumed that in the event of a cascading failure only the largest single contiguous part of a network remains viable.  Whilst this measure is of some use, it fails to recognise that merely isolating infrastructure components does not necessarily mean they fail.  For example, dry roads within a town that has been cut off by floodwater, will still function even if the roads into the town do not.
2. It is possible to influence the nature of the failure propagation between coupled networks by allowing nodes in a given network to have multiple supporting nodes in another network.  For example, providing a back up power supply.
3. Previous studies have shown that removing interdependent links reduces the chance of cascading failure.  However, we find that this is counterproductive when you consider the nature of infrastructure systems and that one infrastructure network often requires a certain degree of interdependence with another in order to be viable..  For example, flooding of a road network may impact our ability to access railway stations, having a knock-on impact upon train use.  Obviously, removing all road-rail connections will ensure the rail network does not receive a minimum amount of passengers, goods, and personnel in order to operate.

Finally, we propose the use of permutable or adaptable systems as efficient and effective mechanisms to give network of network systems rewiring capabilities.  These permutable nodes and links appear to protect coupled networks from the destructive consequences of isolation and cascading failure and at the same time preserve network resources by limiting the amount of redundancy needed to absorb a disturbance.  These permutable systems are different from multi-service conduits.  For example, an electric line that carries phone communications at the same time would propagate failure through both phone and electricity networks in case of malfunction while, on the other hand, components that can provide alternated states of coupling to different networks limit the topological propagation of cascading failure while providing an alternate configuration to the system because of their rewiring capabilities.  Examples include roads convertible to landing strips, tunnels that can alternate between traffic and storm water management (e.g. the Stormwater Management and Road Tunnel (SMART) in Kuala Lumpur), energy storage devices on board electric vehicles that can be plugged to the power grid when not in use so as to store and produce energy whenever needed.

Read the full article for free:
Khoury M, Bullock S, Fu G, and Dawson RJ (2015) Improving measures of topological robustness in networks of networks and suggestion of a novel way to counter both failure propagation and isolation, J. Infrastructure Complexity, 2(1):1-20.

Experts from Newcastle University’s Centre for Earth Systems Enginering Resarch fear for water supplies and wildlife. Mountains may be hotting up faster than previously thought with potentially dramatic consequences, fear North scientists. An international team of experts, including researchers from Newcastle University, is now calling for urgent and rigorous monitoring of temperature patterns in mountain regions. This could lead to threats ranging from water shortages and the possible extinction of some alpine plants and animal life. Co-authors of the research, Prof Hayley Fowler and Dr Nathan Forsythe, from Newcastle University’s School of Civil Engineering and Geosciences, have been working on climate change in the Himalayas for over a decade. Prof Fowler said: “Changes to climate, glaciers and snow cover in the high mountains of Asia are of vital importance for water supplies to a fifth of the world’s population, so understanding past changes are key to understanding what might happen in the future.” Lead author, Dr Nick Pepin of the University of Portsmouth, said: “Most current predictions are based on incomplete and imperfect data, but if we are right and mountains are warming more rapidly than other environments, the social and economic consequences could be serious, and we could see much more dramatic changes much sooner than previously thought.” The most striking evidence that mountain regions are warming more rapidly than surrounding regions comes from the Tibetan plateau. Here temperatures have risen steadily over the past 50 years and the rate of change is speeding up. But masked by this general climate warming are pronounced differences at different elevations. For example, over the past 20 years temperatures above 4,000 metres have warmed nearly 75% faster than temperatures in areas below 2,000 metres. The team of scientists came together as part of the Mountain Research Initiative, a mountain global change research effort funded by the Swiss National Foundation. Between them, they have studied data on mountain temperatures worldwide collected over the past 60-70 years. Dr Pepin said: “There is growing evidence that high mountain regions are warming faster than lower elevations and such warming can accelerate many other environmental changes such as glacial melt and vegetation change, but scientists urgently need more and better data to confirm this.” Among the reasons the researchers examined for faster rates of temperature increase in mountain regions are: •Loss of snow and ice, leading to more exposed land surface at high elevation warming up faster in the sun; •Increasing release of heat in the high atmosphere. A warmer atmosphere holds more moisture, which, when condensing as clouds at high elevation, releases more heat to the mountain environment; •Aerosol pollutants at low elevations, including haze, dust and smoke, reduces warming at those elevations, thus increasing the difference in rates of warming between low and high elevations; •Dust and soot deposited on the surface at high elevations causes more incoming sunlight to be converted to heat. •The world’s highest mountain, Mt Everest, stands at 8,848 m. More than 250 other mountains, including Mt Elbrus in Russia, Mt Denali in Alaska, Mt Aconcagua in Argentina and Mt Kilimanjaro in Africa, also all top the 5,000m mark. Ben Nevis, in Scotland, is the UK’s highest mountain, standing at 1,344 m.

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Full paper: Pepin, N., Bradley, N.S., Diaz, H.F., Baraer, M., Caceres, E.B., Forsythe, N., Fowler, H.J., Greenwood, G., Hashmi, M.Z., Liu, X.D., Miller, J., Ning, L., Ohmura, A., Palazzi, E., Rangwala, I., Schoener, W., Severskiy, I., Shahgedanova, M., Wang, M.B., Williamson S.N., and Yang, D.Q. 2015. Elevation-Dependent Warming in Mountain Regions of the World. Nature Climate Change 5, 424–430 doi:10.1038/nclimate2563