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FEATURE ARTICLE

Gifts and Perils of Landslides

Catastrophic rockslides and related landscape developments are an integral part of human settlement along upper Indus streams

Kenneth Hewitt

Life in a Catastrophic Landscape

If the larger landslides are indeed triggered by megaearthquakes, it means that rare, seismo-tectonic events punctuate, reset and, ultimately, control the landscape agenda. The landslide-related features along the Indus streams support such a view. They comprise indirect and drawn-out, post-landslide responses, or “relaxation” phases, following landslide shocks. They develop on millennial time scales and, coincidentally, create conditions favorable to generations of human habitation.

2010-09HewittSidebar.jpgClick to Enlarge ImageMore sobering, however, are the rare but cataclysmic hazards implied: events that combine great earthquakes with multiple large landslides, river valleys inundated above, and starved of sediment and water below, for centuries at least. And no capacity presently exists to predict, let alone prevent, events on such scales. Certainly, more could and should be done to adopt and enforce higher levels of structural safety for buildings, which could at least save lives away from megaearthquake epicenters and landslide run-out zones. Regional preparedness, if more effective than in recent earthquake disasters, could improve survival and recovery possibilities. For the moment, however, expanding towns and cities, along with large-scale infrastructure, notably big dams and highways, are increasing the concentrations of people and structures at risk.

Through most of history land use in the Himalaya was organized around widely scattered villages and smallish centers. Today, such an approach is commonly treated as outmoded—a less efficient form of existence—and in many cases traditional risk-averting arrangements and environmental knowledge are being undermined or lost. On the other hand, the inhabitants may carry a deep structure of historical understanding about collective security for living with a catastrophically generated land base. Their landslide stories may be more realistic than fatalistic in coming to terms with such an environment.

Finally, although the Karakoram has exceptional numbers, landslides and landslide-related developments clearly exist in other mountains. Examples are known, and the list grows rapidly, throughout High Asia, in the western cordilleras of the Americas, the European and New Zealand Alps, and the Caucasus. In some of these, too, indications of rare megaearthquakes are being investigated. The situation supports calls for a revised concept of the drivers of landform development in high mountains, and a rethinking of responses to the geohazards involved.

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