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1.
Chien-Yuan Chen 《Landslides》2016,13(1):153-164
Typhoon Morakot brought extreme rainfall and initiated numerous landslides and debris flows in southern Taiwan in August of 2009. The purpose of this study is to identify the extreme rainfall-induced landslide frequency-area distribution in the Laonong River Basin in southern Taiwan and debris flow-initiated conditions under rainfall. Results of the analysis show that debris flows were initiated under high cumulative rainfall and long rainfall duration or high rainfall intensity. The relationship of mean rainfall intensity and duration threshold could reflect debris flow initiation characteristics under high rainfall intensity in short rainfall duration conditions. The relationship of cumulative rainfall and duration threshold could reflect debris flow initiation characteristics under high cumulative rainfall in long rainfall duration. Defining rainfall events by estimating rainfall parameters with different methodologies could reveal variations among intermittent rainfall events for the benefit of issuing debris flow warnings. The exponent of landslide frequency-area distribution induced by Typhoon Morakot is lower than that induced by the Chi-Chi earthquake. The lower exponent of landslide frequency-area distribution can be attributed to the transportation and deposition areas of debris flow that are included in the landslide area. Climate change induced high rainfall intensity and long duration of precipitation, for example, Typhoon Morakot brought increased frequency of debris flow and created difficulty in issuing warnings from rainfall monitoring. 相似文献
2.
Chien-Yuan CHEN 《山地科学学报》2012,9(4):463-471
Defining a basin under a critical state(or a self-organized criticality) that has the potential to initiate landslides,debris flows,and subsequent sediment disasters,is a key issue for disaster prevention.The Lushan Hot Spring area in Nantou County,Taiwan,suffered serious sediment disasters after typhoons Sinlaku and Jangmi in 2008,and following Typhoon Morakot in 2009.The basin’s internal slope instability after the typhoons brought rain was examined using the landslide frequency-area distribution.The critical state indices attributed to landslide frequency-area distribution are discussed and the marginally unstable characteristics of the study area indicated.The landslides were interpreted from Spot 5 images before and after disastrous events.The results of the analysis show that the power-law landslide frequency-area curves in the basin for different rainfall-induced events tend to coincide with a single line.The temporal trend of the rainfallinduced landslide frequency-area distribution shows 1/f noise and scale invariance.A trend exists for landslide frequency-area distribution in log-log space for larger landslides controlled by the historical maximum accumulated rainfall brought by typhoons.The unstable state of the basin,including landslides,breached dams,and debris flows,are parts of the basin’s self-organizing processes.The critical state of landslide frequency-area distribution could be estimated by a critical exponent of 1.0.The distribution could be used for future estimation of the potential landslide magnitude for disaster mitigation and to identify the current state of a basin for management. 相似文献
3.
A case study of coseismic landslides and post-seismic sedimentary impacts of landslides due to rainfall events was conducted in the Tachia River basin, Taichung County, central Taiwan. About 3000 coseismic landslides occurred in the basin during the ML 7.3 Chi-Chi earthquake in 1999. The deposits from these landslides provided material for numerous debris flows induced by subsequent rainfall events. The estimated 4.1 × 107 m3 of landslide debris produced in the upland area caused sediment deposition in riverbeds, and flash floods inundated downstream areas with sediment during torrential rains. The landslide frequency-size distributions for the coseismic landslides and the subsequent rainfall-induced landslides were analyzed to determine the sediment budgets of the post-seismic geomorphic response in the landslide-dominated basin. Both the coseismic and the rainfall-induced landslides show a power–law frequency-size distribution with a rollover. It was found that the rainfall-induced landslide magnitude was smaller than the coseismic one, and that both have comparable negative scaling exponents in cumulative form, of about − 2.0 for larger landslides (> 10− 2 km2). This may be attributed to ongoing movement or reactivation of old landslides, and a natural stabilisation of small landslides between 10− 4 and 10− 2 km2. It is proposed that the characteristics of geological formations and rainfall as well as changes in landslide area are reflected in the power–law distribution. 相似文献
4.
Chen Chien-Yuan Chen Lien-Kuang Yu Fan-Chieh Lin Sheng-Chi Lin Yu-Ching Lee Chou-Lung Wang Yu-Ting Cheung Kei-Wai 《Natural Hazards》2008,47(2):245-261
Typhoon Haitang caused landfall on Taiwan during 15–21 July, 2005 and brought 2,279 mm of maximum cumulative rain with a maximum
intensity of 176 mm/h. The torrential rain was mainly distributed from the central mountain range to southern Taiwan and triggered
222 slopeland-related hazards. Among the hazard events, there were 17 debris flows, 157 cases of traffic cut-off, three large-magnitude
deep-seated landslides, and 10 villages isolated in the off-track mountainous areas. The debris flows initiated in southern
Taiwan were associated with torrential rain, short channel length (<2 km), and small basin area (<3 km2), and were speculated to be induced by flash flood. These flash flood-induced debris flows have a higher rainfall intensity-duration
threshold for initiation than in other areas. The deep-seated landslides, isolated villages due to traffic cut-off in off-track
mountain areas, and recurrent hazards in areas affected by the ML 7.6 Chi-Chi earthquake in 1999 are characteristics of slopeland hazards in Taiwan in recent years. One of the most urgently
needed mitigation strategies in response to slopeland hazards is the plan for enhancing self-rescue disaster resistance in
off-track mountainous villages in Taiwan. 相似文献
5.
Fan-Chieh Yu Tien-Chien Chen Meei-Ling Lin Chien-Yuan Chen Wen-Hai Yu 《Natural Hazards》2006,37(1-2):153-167
The severe Typhoon Nari ended on September 15, 2001 with a high-intensity and high-accumulation storm that dumped up to 1249 mm
of rain in Taipei City, Taiwan. The high-intensity and high-accumulation event caused flooding and triggered more than 400
soils slips and debris flows and large, complex landslides. Detailed information on 63 events, including rainfall, initiation
time, and magnitude of landslides were documented and analyzed to identify the landslides and rainfall characteristic in Taipei
City during Typhoon Nari. The result reveals that slump, slide, and debris flow events are associated with the situation of
high-intensity or high-accumulation rainfall. The rainfall intensity-duration condition resulted in smaller magnitude and
shallow failures. Medium to massive landslide were mainly related to the high-accumulation rainfall. A landslide regionalization
process based on rainfall, geomorphologic and geologic characteristics is proposed. Results of the proposed process show good
agreement with landslide events observed in the Taipei City during Typhoon Nari. 相似文献
6.
Improving debris flow monitoring in Taiwan by using high-resolution rainfall products from QPESUMS 总被引：2，自引：2，他引：2
Chien-Yuan Chen Lee-Yao Lin Fan-Chieh Yu Ching-Sheng Lee Chun-Chieh Tseng An-Hsiang Wang Kei-Wai Cheung 《Natural Hazards》2007,40(2):447-461
Debris flow is commonly initiated by torrential rain and its triggering is correlated to the hydrological, geological, and
geomorphic conditions on site. In spite of the important effects of geology and topography, rainfall characteristic is the
main external triggering factor to debris flow and is a predominant parameter for real-time monitoring. Due to the scarcity
of sufficient spatial ground-based rainfall data in hill areas, quantitative precipitation estimation using remote-sensing
techniques such as radar and satellite is needed for debris flow pre-warning. The QPESUMS (Quantitative Precipitation Estimation
and Segregation Using Multiple Sensors) system was acquired to retrieve spatial rainfall data during the rainfall period from
June 30 to July 6 in 2004 when Typhoon Mindulle and southwesterly flow struck Taiwan. The retrieved data were used for setting
up the debris flow monitoring algorithm. With the aid of multiple platforms of meteorological observations, a rainfall threshold
isohyet in a pilot area was mapped for debris flow monitoring. The rainfall monitoring algorithm based on QPESUMS provides
more detailed information than the limited number of ground-based rainfall stations for interpreting the spatial distributions
of rainfall events, and therefore is more suitable for debris-flow monitoring. 相似文献
7.
The geometry of a block is a major factor affecting its rock-fall motion. A two-dimensional disc or three-dimensional sphere
is often used to numerically simulate rock-fall motion, though circular or spherical blocks poorly represent the real geometry
of rock falls. An eccentric circle model is specifically proposed to simulate the behavior of non-circular blocks in rock-fall
motion using the distinct element method. In the eccentric circle model, the moment originates from the eccentricity. Three
types of block shape, circle, ellipse, and eccentric circle, were used to simulate the fall of a single block through four
different slope shapes to impact on a defense wall. The results of the simulation revealed that when the eccentricity falls
below 0.5, the rock-fall motion is close to that of the ellipse model. As eccentricity grows, the rock-fall motion is closer
to that of a flat piece, more stable, and tending to slide. When the block impacts the defensive wall using the circle model,
a higher force and energy head in the wall is obtained. This case tends to be conservative, with the exception of the high
slope angle case. The bouncing height using the circle model falls just between those of the ellipse and the eccentric circle
models and tends to be unconservative. In conclusion, the rock-fall motion simulation using the proposed eccentric circle
model appears to approach the non-circular block trajectory and energy loss, making it useful for rock-fall risk prevention
and mitigation. 相似文献
8.
Earthquake-induced potential landslides are commonly estimated using landslide susceptibility maps. Nevertheless, the fault location is not identified and the ground motion caused by it is unavailable in the map. Thus, potential coseismic landslides for a specific fault motion-induced earthquake could not be predicted using the map. It is meaningful to incorporate the fault location and ground motion characteristics into the landslide predication model. A new method for a specific fault motion-induced coseismic landslide prediction model using GIS (Geographic Information System) is proposed herein. Location of mountain ridges, slope gradients over 45 o , PVGA (Peak Vertical Ground Accelerations) exceeded 0.15 g, and PHGA (Peak Horizontal Ground Accelerations) exceeded 0.25 g of slope units were representing locations that initiated landslides during the 1999 Chi-Chi earthquake in Taiwan. These coseismic landslide characteristics were used to identify areas where landslides occurred during Meishan fault motion-induced strong ground motions in Chiayi County in Taiwan. The strong ground motion (over 8 Gal in the database, 1 Gal = 0.01 m/s 2 , and 1 g = 981 Gal) characteristics were evaluated by the fault length, site distance to the fault, and topography, and their attenuation relations are presented in GIS. The results of the analysis show that coseismic landslide areas could be identified promptly using GIS. The earthquake intensity and focus depth have visible effects on ground motion. The shallower the focus depth, the larger the magnitude increase of the landslides. The GIS-based landslide predication method is valuable combining the geomorphic characteristics and ground motion attenuation relationships for a potential region landslide hazard assessment and in disaster mitigation planning. 相似文献
9.
Chien-Yuan Chen Lien-Kuang Chen Fan-Chieh Yu Sheng-Chi Lin Yu-Ching Lin Chou-Lung Lee Yu-Ting Wang 《Environmental Earth Sciences》2010,59(8):1693-1702
Typhoons Aere (2004) and Matsa (2005) caused high nephelometric turbidity in the Shihmen reservoir in northern Taiwan, jeopardizing
the operation of the reservoir for several days, and ultimately impacting the living conditions and economy of the downstream
residents. The torrential rains caused landslides and debris flows in upland areas, and flowed into riverbeds, likely contributing
significantly to the suspended sediment yields in the reservoir. This investigation elucidates how upland landslides affect
sediment attributes in the reservoir basin. Study methods including field observations, spatial analysis in GIS and aerial
photo interpretation are adopted to trace the sediment sources and contributing factors to the landslide. Torrential rains
induced landslides and debris-flows upland, causing river incisions and soil erosion in landslide areas lacking vegetation.
These factors, together with the conditions of the engineered structures and geologic vulnerabilities of the area, caused
suspended sediment yield in the reservoir. The high nephelometric turbidity could potentially reoccur, with masses of landslide-derived
sediment remaining upland and in the riverbed. 相似文献
10.
Chien-Yuan Tseng Huai-Jen Yang Houng-Yi Yang Dunyi Liu Cailai Wu Chiu-Kuang Cheng Cheng-Hong Chen Choon-Muar Ker 《Gondwana Research》2009,16(2):285
Adakitic intrusive rocks of 430–450 Ma were discovered in the North Qilian orogenic belt, the western section of the Central Orogenic System (COS) in China. These adakitic rocks were lower crust melts rather than slab melts as indicated by their crustal Ce/Pb, Nb/U, Ti/Eu, and Nd/Sm ratios and radiogenically enriched (87Sr/86Sr)i of 0.7053–0.7066 and εNd(t) of − 0.9 to − 1.7. While they are all characterized by low Yb (< 1.1 ppm) and Y (< 11.5 ppm) abundances with high Sr/Y (> 65) and (La/Yb)N (> 13.7) ratios, these adakitic rocks are classified into the low-MgO–Ni–Cr and high-MgO–Ni–Cr groups. The low-MgO samples were derived from partial melting of thickened lower crust, whereas the high-MgO samples were melts from delaminated lower crust, which subsequently interacted with mantle peridotite upon ascent. Adakitic rocks from the adjacent North Qinling orogenic belt also originated from thickened lower crust at 430 Ma. In addition, the North Qilian and North Qinling orogenic belts both consist of lithological assemblages varying from subduction-accretionary complexes at south to central arc assemblages, which include adakitic rocks, then to backarc phases at north. Such a sequence reflects northward subduction of the Qilian and Qinling oceans. In these two orogenic belts, the occurrence of adakitic rocks of common origin and ages together with the similarities in tectonic configurations and lithological assemblages are considered to be the evidence for the continuity between eastern Qilian and western Qinling, forming a > 1000 km Early Paleozoic orogenic belt. In such a tectonic configuration, the Qilian and Qinling oceans that subducted from south possibly represent parts of the large “Proto-Tethyan Ocean”. This inference is supported by the coexistence of Early Paleozoic coral and trilobite specimens from Asia, America and Australia in the North Qilian orogenic belt. Post-400 Ma volcanic rocks occur in the North Qinling orogenic belt but are absent in the North Qilian orogenic belt, indicating that these two orogenic belts underwent distinct evolution history after the closure of the Proto-Tethyan Ocean ( 420 Ma). 相似文献