LANDSLIDE

Landslide

Landslide

Almost every day a landslide disaster occurs somewhere in the world. Nearly any time there is heavy rainfall, an earthquake, a volcanic eruption, strong wave action on a shoreline, or some ill-considered alteration of sloping land by humans, landslides occur.

In a world of persistent and increasing construction on and occupation of hillslopes, canyons, and coastal bluffs, landslides are exacting an inexorable toll of human life and economic loss. In the 1980's, massive landslide disasters occurred throughout the world, many in regions where such disasters were historically unprecedented. or where their potential was forgotten or disregarded by present generations. In some cases, large populations had moved onto unstable lands before renewed landslide activity. For example, the San Francisco Bay region in California doubled in population between 1955 and 1982, and much of the new development occurred on hillsides and in canyons. Major rainstorms in both 1955 and 1982 produced abundant landslides throughout the region, but the landslides in 1982 proved much more devastating than those in 1955 because of the increased population density on sloping ground. Similar situations persist in many other population centers surrounded by hills and mountains, such as Rio de Janeiro, Hong Kong, and Los Angeles.

In other recent disasters, subtle influences of climatic change may be at play. The September 1987 debris-flow disaster in the European Alps resulted from widespread mobilization of high-altitude glacial debris by heavy rainfall. Historical records show that much of this debris was covered by glacial ice and not exposed to rainfall until many glaciers began to recede during the 20th century. Similar catastrophic potential may exist in Nepal, China, Canada, and other countries with steep mountains capped by receding glaciers.

Although not yet firmly documented, climatic change may also be responsible for unusually severe rainstorms, such as the one that devastated South Korea in September, 1990, or anomalous storms that generate very high waves such as those that pounded the California coast in 1983. Such storms give rise to slope instability and an increase in landslide activity.

Scientific investigations of the past 10 to 20 years reveal that much of the Earth's surface, including its seafloors, has landslide potential. These landslide hazard areas include active landslides, landslide deposits representing past activity, and other surficial deposits that can readily turn into landslides because of human activities or changing environmental conditions. Because of this and the appalling human suffering caused by landslides, it is not surprising that landslides are rapidly becoming the focus of major scientific research and changes in land-use policy throughout the world.

Although landslides are natural phenomena, their occurrence is exacerbated by human activities. Landslides can exist in many forms, as well as the spatial location on the Earth's surface. Research in such cases depends on the place, depending on factors including the level of economic development, education and understanding, as well as the public. (Zuoan, Wang, Wang, 2006) There is no doubt that the emergence of landslides such as landslides, debris flows and rotational sliding due to natural processes operating ...