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Applications of simulation technique on debris-flow hazard zone delineation: a case study in Hualien County, Taiwan  [PDF]
S. M. Hsu,L. B. Chiou,G. F. Lin,C. H. Chao
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2010,
Abstract: Debris flows pose severe hazards to communities in mountainous areas, often resulting in the loss of life and property. Helping debris-flow-prone communities delineate potential hazard zones provides local authorities with useful information for developing emergency plans and disaster management policies. In 2003, the Soil and Water Conservation Bureau of Taiwan proposed an empirical model to delineate hazard zones for all creeks (1420 in total) with potential of debris flows and utilized the model to help establish a hazard prevention system. However, the model does not fully consider hydrologic and physiographical conditions for a given creek in simulation. The objective of this study is to propose new approaches that can improve hazard zone delineation accuracy and simulate hazard zones in response to different rainfall intensity. In this study, a two-dimensional commercial model FLO-2D, physically based and taking into account the momentum and energy conservation of flow, was used to simulate debris-flow inundated areas. Sensitivity analysis with the model was conducted to determine the main influence parameters which affect debris flow simulation. Results indicate that the roughness coefficient, yield stress and volumetric sediment concentration dominate the computed results. To improve accuracy of the model, the study examined the performance of the rainfall-runoff model of FLO-2D as compared with that of the HSPF (Hydrological Simulation Program Fortran) model, and then the proper values of the significant parameters were evaluated through the calibration process. Results reveal that the HSPF model has a better performance than the FLO-2D model at peak flow and flow recession period, and the volumetric sediment concentration and yield stress can be estimated by the channel slope. The validation of the model for simulating debris-flow hazard zones has been confirmed by a comparison of field evidence from historical debris-flow disaster data. The model can successfully replicate the influence zone of the debris-flow disaster event with an acceptable error and demonstrate a better result than the empirical model adopted by the Soil and Water Conservation Bureau of Taiwan.
Hydrologic response of a semi-arid watershed to spatial and temporal characteristics of convective rain cells
H. Yakir ,E. Morin
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2011,
Abstract: Rain can be measured and represented in many ways such as point data from rain gauges, grid data from meteorological radar, or interpolated data. In this paper we represent rain fields by implementing a rain cell model of convective rain cells. The rain fields are used as an input to a hydrological model to test the watershed response to spatial and temporal characteristics of the rain cells. As a case study we tested an extreme storm event over a semi-arid watershed in southern Israel. The rain cell model was found to simulate the rain storm adequately. The use of these modeled cells allowed us to test the sensitivity of the watershed hydrological response to rain cell characteristics and it was found that the watershed is mainly sensitive to the starting location of the rain cell. Relatively small changes in the rain cell's location, speed and direction may increase watershed peak discharge by three-fold.
Hydrologic response of a semi-arid watershed to spatial and temporal characteristics of convective rain cells
H. Yakir,E. Morin
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-7725-2010
Abstract: Rain can be measured and represented in many ways such as point data from rain gauges, grid data from meteorological radar, or interpolated data. In this paper we represent rain fields by implementing a rain cell model of convective rain cells. The rain fields are used as an input to a hydrological model to test the watershed response to spatial and temporal characteristics of the rain cells. As a case study we tested an extreme storm event over a semi-arid watershed in southern Israel. The rain cell model was found to simulate the rain storm adequately. The use of these modeled cells allowed us to test the sensitivity of the watershed hydrological response to rain cell characteristics and it was found that the watershed is mainly sensitive to the starting location of the rain cell. Relatively small changes in the rain cell's location, speed and direction may increase watershed peak discharge by three-fold.
Construction of Ecological Function Network in Regional Scale: A Case Study in Taiwan Island
区域尺度生态功能网络构建 ———以中国台湾岛为例

CHANG Hsiaofei,WANG Yanglin,LI Zhengguo,HSUEH Ichen,
张小飞
,王仰麟,李正国,薛怡珍

地理科学进展 , 2007,
Abstract: Constructing ecological network could protect environment, stabilize ecology and enhance ecological value of urban open space. Regional ecological network based on administerial units could represent natural characteristics and ecological function diversity of study area and could guide regional landscape ecological optimizing. In order to highlight the importance of ecological function network of each county or city on the whole Taiwan island and to guide establishing county or city development strategies, this study intends to construct ecological function network in the whole island through researches in counties or cities, and to separately integrate indices of ecological benefit, ecological patterns, and etc. At present, ecological function network centers in Taiwan locate in Hualien and Nantou counties, and ecological function wears off from east to west. Thereafter, according to function network framework, ecological needs estimation, and land value evaluation, this study suggests that Taipei city and other counties should improve their environments.
Monitoring and Predicting Land-use Changes and the Hydrology of the Urbanized Paochiao Watershed in Taiwan Using Remote Sensing Data, Urban Growth Models and a Hydrological Model  [PDF]
Yu-Pin Lin,Yun-Bin Lin,Yen-Tan Wang,Nien-Ming Hong
Sensors , 2008, DOI: 10.3390/s8020658
Abstract: Monitoring and simulating urban sprawl and its effects on land-use patterns andhydrological processes in urbanized watersheds are essential in land-use and waterresourceplanning and management. This study applies a novel framework to the urbangrowth model Slope, Land use, Excluded land, Urban extent, Transportation, andHillshading (SLEUTH) and land-use change with the Conversion of Land use and itsEffects (CLUE-s) model using historical SPOT images to predict urban sprawl in thePaochiao watershed in Taipei County, Taiwan. The historical and predicted land-use datawas input into Patch Analyst to obtain landscape metrics. This data was also input to theGeneralized Watershed Loading Function (GWLF) model to analyze the effects of futureurban sprawl on the land-use patterns and watershed hydrology. The landscape metrics ofthe historical SPOT images show that land-use patterns changed between 1990–2000. TheSLEUTH model accurately simulated historical land-use patterns and urban sprawl in thePaochiao watershed, and simulated future clustered land-use patterns (2001–2025). TheCLUE-s model also simulated land-use patterns for the same period and yielded historical trends in the metrics of land-use patterns. The land-use patterns predicted by the SLEUTHand CLUE-s models show the significant impact urban sprawl will have on land-usepatterns in the Paochiao watershed. The historical and predicted land-use patterns in thewatershed tended to fragment, had regular shapes and interspersion patterns, but wererelatively less isolated in 2001–2025 and less interspersed from 2005–2025 compared withland-use pattern in 1990. During the study, the variability and magnitude of hydrologicalcomponents based on the historical and predicted land-use patterns were cumulativelyaffected by urban sprawl in the watershed; specifically, surface runoff increasedsignificantly by 22.0% and baseflow decreased by 18.0% during 1990–2025. The proposedapproach is an effective means of enhancing land-use monitoring and management ofurbanized watersheds.
Monitoring and Predicting Land-use Changes and the Hydrology of the Urbanized Paochiao Watershed in Taiwan Using Remote Sensing Data, Urban Growth Models and a Hydrological Model
Yu-Pin Lin,Yun-Bin Lin,Yen-Tan Wang,Nien-Ming Hong
Sensors , 2008,
Abstract: Monitoring and simulating urban sprawl and its effects on land-use patterns andhydrological processes in urbanized watersheds are essential in land-use and waterresourceplanning and management. This study applies a novel framework to the urbangrowth model Slope, Land use, Excluded land, Urban extent, Transportation, andHillshading (SLEUTH) and land-use change with the Conversion of Land use and itsEffects (CLUE-s) model using historical SPOT images to predict urban sprawl in thePaochiao watershed in Taipei County, Taiwan. The historical and predicted land-use datawas input into Patch Analyst to obtain landscape metrics. This data was also input to theGeneralized Watershed Loading Function (GWLF) model to analyze the effects of futureurban sprawl on the land-use patterns and watershed hydrology. The landscape metrics ofthe historical SPOT images show that land-use patterns changed between 1990 ¢ € “2000. TheSLEUTH model accurately simulated historical land-use patterns and urban sprawl in thePaochiao watershed, and simulated future clustered land-use patterns (2001 ¢ € “2025). TheCLUE-s model also simulated land-use patterns for the same period and yielded historical trends in the metrics of land-use patterns. The land-use patterns predicted by the SLEUTHand CLUE-s models show the significant impact urban sprawl will have on land-usepatterns in the Paochiao watershed. The historical and predicted land-use patterns in thewatershed tended to fragment, had regular shapes and interspersion patterns, but wererelatively less isolated in 2001 ¢ € “2025 and less interspersed from 2005 ¢ € “2025 compared withland-use pattern in 1990. During the study, the variability and magnitude of hydrologicalcomponents based on the historical and predicted land-use patterns were cumulativelyaffected by urban sprawl in the watershed; specifically, surface runoff increasedsignificantly by 22.0% and baseflow decreased by 18.0% during 1990 ¢ € “2025. The proposedapproach is an effective means of enhancing land-use monitoring and management ofurbanized watersheds.
Characteristics of rainfall triggering of debris flows in the Chenyulan watershed, Taiwan  [PDF]
J. C. Chen,C. D. Jan,W. S. Huang
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2013, DOI: 10.5194/nhess-13-1015-2013
Abstract: This paper reports the variation in rainfall characteristics associated with debris flows in the Chenyulan watershed, central Taiwan, between 1963 and 2009. The maximum hourly rainfall Im, the maximum 24 h rainfall Rd, and the rainfall index RI (defined as the product RdIm) were analysed for each rainfall event that triggered a debris flow within the watershed. The corresponding number of debris flows initiated by each rainfall event (N) was also investigated via image analysis and/or field investigation. The relationship between N and RI was analysed. Higher RI of a rainfall event would trigger a larger number of debris flows. This paper also discusses the effects of the Chi-Chi earthquake (CCE) on this relationship and on debris flow initiation. The results showed that the critical RI for debris flow initiation had significant variations and was significantly lower in the years immediately following the CCE of 1999, but appeared to revert to the pre-earthquake condition about five years later. Under the same extreme rainfall event of RI = 365 cm2 h 1, the value of N in the CCE-affected period could be six times larger than that in the non-CCE-affected periods.
A Semi-Empirical Model of Rain Attenuation at Ka-Band in Northern Taiwan
Kun-Shan Chen;Chih-Yuan Chu;Yu-Chang Tzeng
PIER M , 2011, DOI: 10.2528/PIERM10100303
Abstract: Combining a two-year measurement and numerical approach, a semi-empirical model has been developed for prediction of rain attenuation at Ka-band in northern Taiwan. This was done using the drop size distribution (DSD) measurement and the extinction coefficient calculated by T-matrix, followed by regressing with rain attenuation measurements in all seasons. The attenuation due to rain can be estimated by calculating the extinction coefficient over all of the rain drops within the antenna beam volume. Comparing with the measured data demonstrates that the proposed model proves sufficiently accurate for Ka-band signal attenuation in site specific. For purpose of cross reference, we also compared the proposed model with Crane and ITU-R-P838 rain attenuation models. The RMS error and chi-square test shows that the proposed semi-empirical model has better performance to predicted rain attenuation than Crane and ITU-RP383 models, implied that both model predictions may not be quite reliable in some specific areas. Analysis suggests that seasonal effects are strong in signal attenuation due to rain types. It means that rain rate itself is not a quite reliable enough to be the single parameter in the rain attenuation model.
A Mesoscale Analysis of Heavy Rain Caused by Frontal and Topographical Heterogeneities on Taiwan Island
JING Li,LU Hancheng,WANG Hanjie,ZHU Min,KOU Zheng,
JING Li
,LU Hancheng,WANG Hanjie,ZHU Min,KOU Zheng

大气科学进展 , 2004,
Abstract: The prevailing mesoscale model MM5 (V3) is used to simulate a heavy rain case caused by interaction between a move-in front and topographical heterogeneities on Taiwan Island. It is found that both thermodynamic and dynamic fields along the front are heterogeneous in time and space. The heterogeneity becomes more significant as the effect of topography is added on. The heterogeneous distribution of physical variables along the front is the main reason for the heterogeneous frontal rain band; the optimum cooperation of the low level and upper level jet is another reason for the development of the rain band.Topography can strengthen the rainfall and causes extremely heavy rain cells. Updraft induced by topography extends to a rather low level, while the uplifted air by frontal circulation can reach to higher levels.The quasi-steady topographic circulation overlaps the frontal circulation when the front moves over Taiwan Island; the advantageous cooperation of various mesoscale conditions causes the large upward velocity on the windward side of the island.
Estimation of runoff and sediment yield in the Redrock Creek watershed using AnnAGNPS and GIS
Tsou Ming-Shu,ZHAN Xiao-yong,
Tsou Ming-Shu
,ZHAN Xiao-yong

环境科学学报(英文版) , 2004,
Abstract: Sediment has been identified as a significant threat to water quality and channel clogging that in turn may lead to river flooding. With the increasing awareness of the impairment from sediment to water bodies in a watershed, identifying the locations of the major sediment sources and reducing the sediment through management practices will be important for an effective watershed management. The annualized agricultural non-point source pollution(AnnAGNPS) model and newly developed GIS interface for it were applied in a small agricultural watershed, Redrock Creek watershed, Kansas, in this pilot study for exploring the effectiveness of using this model as a management tool. The calibrated model appropriately simulated monthly runoff and sediment yield through the practices in this study and potentially suggested the ways of sediment reduction through evaluating the changes of land use and field operation in the model for the purpose of watershed management.
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