Landslide erosion has an established history in New Zealand. Some broad estimates of economic costs for short-term event
damage, long-term landslide damage, and proactive measures are provided and compared on a national and international level.
Frequency and magnitude analysis based on historical records of landslide-triggering rainstorms demonstrates that 1) landslides
are a nationwide problem, 2) recognition and recording of these events is dependent on public awareness and therefore related
to population distribution and extent of urbanized areas, and 3) deforestation increases the frequency of landslide events,
but not necessarily the total magnitude of their impact. However, some regions such as Northland and Wellington in the North
Island and Greymouth and North Otago in the South Island are more frequently and more strongly affected than others. Landslide
occurrence in time and space, within representative study areas in Hawke's Bay, Wairarapa, and Wellington, is correlated with
the climatic variable daily precipitation. Different regional hydrological thresholds for landslide triggering are established.
Received: 15 Ocotober 1997 · Accepted: 25 June 1997 相似文献
Landslide susceptibility and hazard zoning can notably improve land-use planning, and thus can be considered an efficient way to reduce future damage and loss of lives caused by landslides. However, the lack of standard procedures restricts the use of susceptibility and hazard-zoning maps, notwithstanding their extensive development over the last decades.JTC-1, the Joint Technical Committee on Landslides and Engineered Slopes, fills this void by proposing International Guidelines for Landslide Susceptibility, Hazard and Risk Zoning for land-use planning, which provide definitions, terminology and international standards for methods, levels, scales and types of zoning. The Guidelines also promote the use of quantitative risk-management principles, essential to compare risk from landslides with risks related to other hazards and with loss of life tolerance criteria.This paper focuses on the applicability of landslide susceptibility and hazard zoning at different scales. Several zoning examples, referring to active, dormant and occasionally reactivated slides, provide insights into and highlight the relationships among different methods, levels and types of zoning. The examples also stress the importance of a correct characterization of the processes leading to landsliding to produce reliable susceptibility and hazard-zoning maps. 相似文献
In this paper a tool for semi-quantitative susceptibility assessment at a regional scale is presented which is applicable
at areas with complex geological setting. At a study area within the Northern Calcareous Alps geotechnical mappings were implemented
into a Geographical Information System and analysed as grid data with a cell size of 25 m. The susceptibility to sliding and
falling processes was considered according to five classes (very low, low, medium, high, very high). Susceptibility to sliding
was analysed using an index method. The layers of lithology, bedding conditions, tectonic faults, slope angle, slope aspect,
vegetation and erosion were combined iteratively. Dropout zones of rockfall material were determined with help of a Digital
Elevation Model. The movement of rolling rock samples was modelled by a cost analysis of all potential rockfall trajectories.
These trajectories were also divided into five susceptibility classes. The susceptibility maps are presented in a general
way to be used by communities and spatial planners. Conflict areas of susceptibility and landuse were located and can be presented
destinctively. 相似文献
The identification of extremely high indoor radon concentrations in the village Umhausen (Tyrol, Austria) initiated a scientific program to get information about the source and distribution of this noble gas. The high concentrations can not be related to U anomalies or large-scale fault zones. The nearby giant landslide of Koefels, with its highly fractured and crushed orthogneisses, are the only possible source of radon, despite the fact that the U and Ra content of the rocks is by no means exceptional. The reasons for the high emanation rates from the landslide are discussed and compared to results gained from a similar examination of the giant landslide of Langtang Himal (Nepal). The exceptional geologic situation in both cases, as well as the spatial distribution of different concentration levels, indicate that both landslides must be considered as the production sites of radon. Independent of the U and Ra contents of the rocks, the most important factors producing high emanation rates are the production of a high active surface area and circulation pathways for Rn-enriched soil air by brittle deformation due to the impact of the landslidemass. 相似文献
Two landsliding episodes between late 1973 and early 1975 delivered about 60000 m3 of sediment to six small deeply incised streams draining a 2·7 km2 area. About 4700 m3 of logs in the landslide debris formed major log jams in five streams, which impounded large volumes of landslide-derived sediment. Five years after the landsliding, 42 per cent (25000 m3) of sediment was still in storage behind 35 log jams ranging from 1·4–8·2 m high. The landsliding episodes have produced multi-stepped stream profiles, aggradation of channel reaches up to 150 m long to mean depths between 1·2 and 4·1 m, reductions in gradient, fining of bed material size, and related changes in bedforms and channel width:depth ratios that seem likely to persist for at least several decades. Sediment presently stored behind log jams is equivalent to between 50 and 220 years normal supply of sediment from hillslopes to stream channels. Long-delayed, large magnitude impacts on higher-order channels may occur if sudden failure of log jams is induced by a large storm at some future date. 相似文献
Damaging landslides in the Appalachian Plateau and scattered regions within the Midcontinent of North America highlight the need for landslide-hazard mapping and a better understanding of the geomorphic development of landslide terrains. The Plateau and Midcontinent have the necessary ingredients for landslides including sufficient relief, steep slope gradients, Pennsylvanian and Permian cyclothems that weather into fine-grained soils containing considerable clay, and adequate precipitation. One commonly used parameter in landslide-hazard analysis that is in need of further investigation is plan curvature. Plan curvature is the curvature of the hillside in a horizontal plane or the curvature of the contours on a topographic map. Hillsides can be subdivided into regions of concave outward plan curvature called hollows, convex outward plan curvature called noses, and straight contours called planar regions. Statistical analysis of plan-curvature and landslide datasets indicate that hillsides with planar plan curvature have the highest probability for landslides in regions dominated by earth flows and earth slides in clayey soils (CH and CL). The probability of landslides decreases as the hillsides become more concave or convex. Hollows have a slightly higher probability for landslides than noses. In hollows landslide material converges into the narrow region at the base of the slope. The convergence combined with the cohesive nature of fine-grained soils creates a buttressing effect that slows soil movement and increases the stability of the hillside within the hollow. Statistical approaches that attempt to determine landslide hazard need to account for the complex relationship between plan curvature, type of landslide, and landslide susceptibility. 相似文献
Active fault zones of Armenia, SE Turkey and NW Iran present a diverse set of interrelated natural hazards. Three regional case studies in this cross-border zone are examined to show how earthquakes interact with other hazards to increase the risk of natural disaster. In northern Armenia, a combination of several natural and man-made phenomena (earthquakes, landslides and unstable dams with toxic wastes) along the Pambak-Sevan-Sunik fault (PSSF) zone lowers from 0.4 to 0.2–0.3g the maximum permissible level (MPL) of seismic hazard that may induce disastrous destruction and loss of life in the adjacent Vanadzor depression.
In the Ararat depression, a large active fault-bounded pull-apart basin at the junction of borders of Armenia, Turkey, Iran and Azerbaijan, an earthquake in 1840 was accompanied by an eruption of Ararat Volcano, lahars, landslides, floods, soil subsidence and liquefaction. The case study demonstrates that natural hazards that are secondary with respect to earthquakes may considerably increase the damage and the casualties and increase the risk associated with the seismic impact.
The North Tabriz–Gailatu fault system poses a high seismic hazard to the border areas of NW Iran, eastern Turkey, Nakhichevan (Azerbaijan) and southern Armenia. Right-lateral strike–slip motions along the North Tabriz fault have given rise to strong earthquakes, which threaten the city of Tabriz with its population of 1.2 million.
The examples illustrate how the concentration of natural hazards in active fault zones increases the risk associated with strong earthquakes in Armenia, eastern Turkey and NW Iran. This generally occurs across the junctions of international borders. Hence, the transboundary character of active faults requires transboundary cooperation in the study and mitigation of the natural risk. 相似文献