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91.
Many landslides are triggered by rainfall. Previous studies of the relationship between landslides and rainfall have concentrated on deriving minimum rainfall thresholds that are likely to trigger landslides. Though useful, these minimum thresholds derived from a log–log plot do not offer any measure of confidence in a landslide monitoring or warning system. This study presents a new and innovative method for incorporating rainfall into landslide modelling and prediction. The method involves three steps: compiling radar reflectivity data in a QPESUMS (quantitative precipitation estimation and segregation using multiple sensors) system during a typhoon (tropical hurricane) event, estimating rainfall from radar data and using rainfall intensity and rainfall duration as explanatory variables to develop a landslide logit model. Given the logit model, this paper discusses ways in which the model can be used for computing probabilities of landslide occurrence for a real‐time monitoring system or a warning system, and for delineating and mapping landslides. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
92.
Jens M. Turowski Niels Hovius Hsieh Meng‐Long Dimitri Lague Chen Men‐Chiang 《地球表面变化过程与地形》2008,33(3):353-363
Lateral erosion in bedrock rivers is an important control on the shape of channel cross‐sections, and the coupling of channels and hillslopes. Recent observations link lateral erosion to the variability of flow. We propose two mechanisms to explain this. One is based on changing shear stress distributions within the channel with varying flood level, the other on the competition between cover and tool effects in fluvial bedrock erosion. We assess these processes for the Liwu River, Taiwan, and conclude that cover and tool effects dominate the partitioning of lateral and vertical erosion in this case. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
93.
94.
Jiunn-Shyang Chiou Chi-Han Chiang Ho-Hsiung Yang Shang-Yi Hsu 《Soil Dynamics and Earthquake Engineering》2011,31(5-6):830-840
This study proposes a procedure for developing seismic fragility curves for a pile-supported wharf. A typical pile-supported wharf, as commonly used in the ports of Taiwan, is chosen for demonstration. For a structural model of the wharf, the deck is modeled by shell elements and the Winkler model is used for the pile–soil system, in which the piles and soils are represented by beam elements and springs, respectively. A pushover analysis with lateral loads distributed according to the fundamental modal shape of the wharf structure is conducted to deduce the capacity curve of the wharf. The procedure for developing fragility curves can be explicitly performed using the spreadsheet platform in Microsoft EXCEL. First, quantitative criteria for damage states are established from the sequence of development of plastic zones. Then a nonlinear static procedure called the Spectrum Capacity Method (CSM) is used to efficiently construct a response matrix of the wharf to 24 earthquake events with differing levels of peak ground acceleration (PGA). Based on the damage criteria and the response matrix, the fragility curves of the wharf can be thus constructed through simple statistical analysis. Shifted lognormal cumulative distribution functions are also employed to better approximate the fragility curves for practical applications. 相似文献
95.
Jun-Jih Liou Yuan-Fong Su Jie-Lun Chiang Ke-Sheng Cheng 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(2):235-251
In studies involving environmental risk assessment, Gaussian random field generators are often used to yield realizations
of a Gaussian random field, and then realizations of the non-Gaussian target random field are obtained by an inverse-normal
transformation. Such simulation process requires a set of observed data for estimation of the empirical cumulative distribution
function (ECDF) and covariance function of the random field under investigation. However, if realizations of a non-Gaussian
random field with specific probability density and covariance function are needed, such observed-data-based simulation process
will not work when no observed data are available. In this paper we present details of a gamma random field simulation approach
which does not require a set of observed data. A key element of the approach lies on the theoretical relationship between
the covariance functions of a gamma random field and its corresponding standard normal random field. Through a set of devised
simulation scenarios, the proposed technique is shown to be capable of generating realizations of the given gamma random fields. 相似文献
96.
An integrated flood risk assessment model for property insurance industry in Taiwan 总被引:13,自引:11,他引:2
Hsu Wen-Ko Huang Pei-Chiung Chang Ching-Cheng Chen Cheng-Wu Hung Dung-Moung Chiang Wei-Ling 《Natural Hazards》2011,58(3):1295-1309
Taiwan is located in an area affected by Northwest Pacific typhoons, which are also one of the most important sources of rainfall
to the island. Unfortunately, the abundant rainfall brought by typhoons frequently produces hazards. In recent years, typhoons
and floods have caused serious damage, especially Typhoon Morakot in 2009. In this study, a probabilistic model is developed
based on historical events which can be used to assess flood risk in Taiwan. There are 4 separate modules in this model, including
a rainfall event module, a hydraulic module, a vulnerability module, and a financial loss module. Local data obtained from
the Taiwan government are used to construct this model. Historical rainfall data for typhoon and flood events that have occurred
since 1960, obtained from the Central Weather Bureau, are used for computing the maximum daily rainfall for each basin. In
addition, the latest flood maps from the Water Resources Agency are collected to assess the probable inundation depth. A case
study using the local data is carried out. Assessment is made to predict possible economic loss from different financial perspectives
such as the total loss, insured loss, and loss exceeding probabilities. The assessment results can be used as a reference
for making effective flood risk management strategies in Taiwan. 相似文献
97.
Variations in pore-water pressure determined by the groundwater table within a riverbank have been investigated and recognized
as an essential factor in determining riverbank stability with respect to mass failure. However, the effect of pore-water
pressure is taken into account for most of the existing riverbank stability models under some simplified assumptions, and
the limitations of predicting ability may arise. To avoid the unrealistic estimation of pore-water pressure distribution,
the new approach proposed here is to couple riverbank stability with groundwater flow modeling, and apply this to tackle the
conjunction effect between river stage and groundwater table. Moreover, riverbank material characteristics and the influence
of infiltration can be taken into consideration via groundwater flow modeling. Two hypothetical examples, stage rising and
stage falling, are used to investigate the capabilities of the present study and two representative methods. The simulated
results show that riverbank failure is triggered particularly during the falling stage, which has been pointed out by other
researchers as well. Furthermore, the riverbank material characteristics predominantly control the occurrence of failure and
should be considered regarding assessment of riverbank stability. Additionally, the effects of parameters indicate that riverbanks
with soil properties of low permeability or high specific yield with great infiltration intensity during the falling stage
have a tendency to riverbank failure. 相似文献
98.
To minimize potential loss of life and property caused by rainfall during typhoon seasons, precise rainfall forecasts have been one of the key subjects in hydrological research. However, rainfall forecast is made difficult by some very complicated and unforeseen physical factors associated with rainfall. Recently, support vector regression (SVR) models and recurrent SVR (RSVR) models have been successfully employed to solve time‐series problems in some fields. Nevertheless, the use of RSVR models in rainfall forecasting has not been investigated widely. This study attempts to improve the forecasting accuracy of rainfall by taking advantage of the unique strength of the SVR model, genetic algorithms, and the recurrent network architecture. The performance of genetic algorithms with different mutation rates and crossover rates in SVR parameter selection is examined. Simulation results identify the RSVR with genetic algorithms model as being an effective means of forecasting rainfall amount. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
99.
Reservoir operation is generally based on the inflows of the upstream catchment of the reservoir. If the arriving inflows can be forecasted, that can benefit reservoir operation and management. This study attempts to construct a long‐term inflow‐forecasting model by combining a continuous rainfall–runoff model with the long‐term weather outlook from the Central Weather Bureau of Taiwan. The analytical results demonstrate that the continuous rainfall–runoff model has good inflow simulation performance by using 10‐day meteorological and inflow records over a 33‐year period for model calibration and verification. The long‐term inflow forecasting during the dry season was further conducted by combining the continuous rainfall–runoff model and the long‐term weather outlook, which was found to have good performance. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
100.
Debris flows have caused enormous losses of property and human life in Taiwan during the last two decades. An efficient and reliable method for predicting the occurrence of debris flows is required. The major goal of this study is to explore the impact of the Chi‐Chi earthquake on the occurrence of debris flows by applying the artificial neural network (ANN) that takes both hydrological and geomorphologic influences into account. The Chen‐Yu‐Lan River watershed, which is located in central Taiwan, is chosen for evaluating the critical rainfall triggering debris flows. A total of 1151 data sets were collected for calibrating model parameters with two training strategies. Significant differences before and after the earthquake have been found: (1) The size of landslide area is proportioned to the occurrence of debris flows; (2) the amount of critical rainfall required for triggering debris flows has reduced significantly, about half of the original critical rainfall in the study case; and (3) the frequency of the occurrence of debris flows is largely increased. The overall accuracy of model prediction in testing phase has reached 96·5%; moreover, the accuracy of occurrence prediction is largely increased from 24 to 80% as the network trained with data from before the Chi‐Chi earthquake sets and with data from the lumped before and after the earthquake sets. The results demonstrated that the ANN is capable of learning the complex mechanism of debris flows and producing satisfactory predictions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献