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Jiun-Huei Jang
Department of Hydraulic and Ocean Engineering, National Cheng Kung University, Tainan City, Taiwan

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Article
Published: 04 May 2021 in Water Resources Management
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Flood risk maps are important references for disaster prevention and emergency response. The accuracy of risk maps is greatly affected by the resolutions of hazard and vulnerability maps. To determine the impact of map resolutions on flood risk analysis, a total of 12 risk maps were generated for Shanhua District, Taiwan, via the integration of hazard and vulnerability maps under two resolutions and three return periods. The hazard, vulnerability, and risk maps were classified into five levels according to flood depth, socio-economic indicators, and their products, respectively. The results show that the downscaling of hazard maps greatly increases the hit rate by 28% and decreases the false alarm rate by 53% in the flood risk analyses of households. In contrast, the downscaling of vulnerability maps only slightly increases the hit rate without an obvious decrease in the false alarm rate. To improve flood risk analysis under time and budget limitations, numerical downscaling of hazard maps should be given higher priority because it reduces the structural errors in hydraulic simulations that cannot be compensated for by the statistical downscaling of vulnerability maps.

ACS Style

Jiun-Huei Jang; Petr Vohnicky; Yen-Lien Kuo. Improvement of Flood Risk Analysis Via Downscaling of Hazard and Vulnerability Maps. Water Resources Management 2021, 35, 2215 -2230.

AMA Style

Jiun-Huei Jang, Petr Vohnicky, Yen-Lien Kuo. Improvement of Flood Risk Analysis Via Downscaling of Hazard and Vulnerability Maps. Water Resources Management. 2021; 35 (7):2215-2230.

Chicago/Turabian Style

Jiun-Huei Jang; Petr Vohnicky; Yen-Lien Kuo. 2021. "Improvement of Flood Risk Analysis Via Downscaling of Hazard and Vulnerability Maps." Water Resources Management 35, no. 7: 2215-2230.

Journal article
Published: 28 January 2021 in Energies
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In this study, long-term wind fields during 1991–2010 from the Climate Forecast System Reanalysis (CFSR) were dynamically downscaled over Taiwan and its offshore islands at a 5 km horizontal resolution using the Weather Research and Forecasting (WRF) model. Simulations of the 10 m (above sea level) dynamically downscaled winds served as the atmospheric forcing for driving a fully coupled wave-circulation model. The sea states of the waters surrounding Taiwan during 1991–2010 were hindcasted to evaluate the offshore wave energy resources and optimal wave energy hotspots. This study reveals that the southeastern offshore waters of Taiwan and the Central Taiwan Strait exhibited the highest mean wave power density (WPD), exceeding 20 kW/m. The annual mean WPD, incidence of the hourly WPD greater than or equal to 4 kW/m, monthly variability index and coefficient of variation of the WPD indicated that the sea areas located between Green Island and Orchid Island (OH_1), southeast of Orchid Island (OH_2), south of the Hengchun Peninsula (OH_3), and north of the Penghu Islands (OH_4) were the optimal hotspots for deploying wave energy converters. The most energetic months were October for OH_1 and OH_2 and November for OH_3 and OH_4, while the wave power was weak from March to June for OH_1, OH_2 and OH_3 and in May for OH_4. The wave direction is prevailingly east-northeast for OH_1, OH_2 and OH_3 and nearly northeast for OH_4. These phenomena reveal that wave power in the waters offshore Taiwan is induced primarily by the northeast (winter) monsoon. The exploitable annual WPD was estimated to be 158.06, 182.89, 196.39 and 101.33 MWh/m for OH_1, OH_2, OH_3 and OH_4, respectively.

ACS Style

Shih-Chun Hsiao; Chao-Tzuen Cheng; Tzu-Yin Chang; Wei-Bo Chen; Han-Lun Wu; Jiun-Huei Jang; Lee-Yaw Lin. Assessment of Offshore Wave Energy Resources in Taiwan Using Long-Term Dynamically Downscaled Winds from a Third-Generation Reanalysis Product. Energies 2021, 14, 653 .

AMA Style

Shih-Chun Hsiao, Chao-Tzuen Cheng, Tzu-Yin Chang, Wei-Bo Chen, Han-Lun Wu, Jiun-Huei Jang, Lee-Yaw Lin. Assessment of Offshore Wave Energy Resources in Taiwan Using Long-Term Dynamically Downscaled Winds from a Third-Generation Reanalysis Product. Energies. 2021; 14 (3):653.

Chicago/Turabian Style

Shih-Chun Hsiao; Chao-Tzuen Cheng; Tzu-Yin Chang; Wei-Bo Chen; Han-Lun Wu; Jiun-Huei Jang; Lee-Yaw Lin. 2021. "Assessment of Offshore Wave Energy Resources in Taiwan Using Long-Term Dynamically Downscaled Winds from a Third-Generation Reanalysis Product." Energies 14, no. 3: 653.

Journal article
Published: 24 December 2020 in Science of The Total Environment
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Under climate change, compound flooding has resulted in severe disasters in coastal areas around the world. In this study, an integrated framework is proposed to determine the range of compound flood risk without the requirement of joint probability analysis between storm surge and rainfall. In the framework, the flood risks are analyzed under four extreme scenarios with/without the compound effect of storm surge and rainfall in the past and the future. From the end of the 20th century to the middle of the 21st century, the worst scenario shows that the flood area significantly increases by 92% for the low-lying coastal areas in southwest Taiwan under the compound effect of storm surge and rainfall if they are fully correlated. In the most optimistic scenario, the flood area slightly increases by 15% without compound effect (only storm surge is considered). To coastal flooding, the synchronization of storm surge and rainfall contributes much more than the climate-induced amplification of individual factors. When storm surge and rainfall happen at the same time, the extent and duration of flooding increase simultaneously under the influence of pluvial and surge-induced flooding. Risk analysis shows an obvious increase of risk level for villages originally at low risks, which require integrated countermeasures against the consequence brought by compound flooding in the future. The framework can be applied in other low-lying coastal areas to quantify the potential impacts on human and environment caused by compound flooding under climate change.

ACS Style

Shih-Chun Hsiao; Wen-Son Chiang; Jiun-Huei Jang; Han-Lun Wu; Wei-Shiun Lu; Wei-Bo Chen; Yun-Ta Wu. Flood risk influenced by the compound effect of storm surge and rainfall under climate change for low-lying coastal areas. Science of The Total Environment 2020, 764, 144439 .

AMA Style

Shih-Chun Hsiao, Wen-Son Chiang, Jiun-Huei Jang, Han-Lun Wu, Wei-Shiun Lu, Wei-Bo Chen, Yun-Ta Wu. Flood risk influenced by the compound effect of storm surge and rainfall under climate change for low-lying coastal areas. Science of The Total Environment. 2020; 764 ():144439.

Chicago/Turabian Style

Shih-Chun Hsiao; Wen-Son Chiang; Jiun-Huei Jang; Han-Lun Wu; Wei-Shiun Lu; Wei-Bo Chen; Yun-Ta Wu. 2020. "Flood risk influenced by the compound effect of storm surge and rainfall under climate change for low-lying coastal areas." Science of The Total Environment 764, no. : 144439.

Preprint content
Published: 04 March 2020
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Sophisticated flood simulation in urban areas is a challenging task due to the difficulties in data acquisition and model verification. This study incorporates three rapid-growing technologies, i.e. volunteered geographic information (VGI), unmanned aerial vehicle (UAV), and computational flood simulation (CFS) to reconstruct the flash flood event occurred in 14 June 2015, GongGuan, Taipei. The high-resolution digital elevation model (DEM) generated by a UAV and the real-time VGI photos acquired from social network are served to establish and validate the CFS model, respectively. The DEM data are resampled based on two grid sizes to evaluate the influence of terrain resolution on flood simulations. The results show that flood scenario can be more accurately modelled as DEM resolution increases with better agreement between simulation and observation in terms of flood occurrence time and water depth. The incorporation of UAV and VGI lower the barrier of sophisticated CFS and shows great potential in flood impact and loss assessment in urban areas.

ACS Style

Yuan-Fong Su; Yan-Ting Lin; Jiun-Huei Jang; Jen-Yu Han. Using unmanned aerial vehicle and volunteered geographic information to sophisticate urban flood modelling. 2020, 2020, 1 -22.

AMA Style

Yuan-Fong Su, Yan-Ting Lin, Jiun-Huei Jang, Jen-Yu Han. Using unmanned aerial vehicle and volunteered geographic information to sophisticate urban flood modelling. . 2020; 2020 ():1-22.

Chicago/Turabian Style

Yuan-Fong Su; Yan-Ting Lin; Jiun-Huei Jang; Jen-Yu Han. 2020. "Using unmanned aerial vehicle and volunteered geographic information to sophisticate urban flood modelling." 2020, no. : 1-22.

Journal article
Published: 21 February 2020 in Remote Sensing
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Many people use smartphone cameras to record their living environments through captured images, and share aspects of their daily lives on social networks, such as Facebook, Instagram, and Twitter. These platforms provide volunteered geographic information (VGI), which enables the public to know where and when events occur. At the same time, image-based VGI can also indicate environmental changes and disaster conditions, such as flooding ranges and relative water levels. However, little image-based VGI has been applied for the quantification of flooding water levels because of the difficulty of identifying water lines in image-based VGI and linking them to detailed terrain models. In this study, flood detection has been achieved through image-based VGI obtained by smartphone cameras. Digital image processing and a photogrammetric method were presented to determine the water levels. In digital image processing, the random forest classification was applied to simplify ambient complexity and highlight certain aspects of flooding regions, and the HT-Canny method was used to detect the flooding line of the classified image-based VGI. Through the photogrammetric method and a fine-resolution digital elevation model based on the unmanned aerial vehicle mapping technique, the detected flooding lines were employed to determine water levels. Based on the results of image-based VGI experiments, the proposed approach identified water levels during an urban flood event in Taipei City for demonstration. Notably, classified images were produced using random forest supervised classification for a total of three classes with an average overall accuracy of 88.05%. The quantified water levels with a resolution of centimeters (

ACS Style

Yan-Ting Lin; Ming-Der Yang; Jen-Yu Han; Yuan-Fong Su; Jiun-Huei Jang. Quantifying Flood Water Levels Using Image-Based Volunteered Geographic Information. Remote Sensing 2020, 12, 706 .

AMA Style

Yan-Ting Lin, Ming-Der Yang, Jen-Yu Han, Yuan-Fong Su, Jiun-Huei Jang. Quantifying Flood Water Levels Using Image-Based Volunteered Geographic Information. Remote Sensing. 2020; 12 (4):706.

Chicago/Turabian Style

Yan-Ting Lin; Ming-Der Yang; Jen-Yu Han; Yuan-Fong Su; Jiun-Huei Jang. 2020. "Quantifying Flood Water Levels Using Image-Based Volunteered Geographic Information." Remote Sensing 12, no. 4: 706.

Article
Published: 01 October 2019 in Water Resources Management
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Accurate real-time forecasts of river stages can serve as a reference for flood evacuation to minimize losses and casualties. Machine learning has been widely used for river stage forecasting because of its simple modeling and quick computation. However, many machine learning models have drawbacks such as excessive learning time, difficult evaluation of input variables, and lack of explanatory capacity, which limit their performance as practical tools. To overcome these drawbacks, this study employs multiple additive regression trees (MART) for river stage forecasting. Three MART models are proposed, namely the original MART model, the real-time MART model, and the naïve MART model, with different considerations of model training and error correction. Model training and testing were conducted based on the rainfall and river stage data for 16 typhoon events between 2005 and 2009 in the Bazhang River Basin in Taiwan. In the training process, variables are automatically selected by the MART models which reasonably describes the mechanism of flood transportation. The testing results show that all three models can reasonably forecast the river stages with a three-hour lead-time. Compared with the original MART, the real-time MART performs better in describing overall river stage variations, whereas the naïve MART is more accurate in the prediction of peak river stages. The proposed MART models are efficient and accurate and can thus serve as practical tools for flash flood early warning.

ACS Style

Jin-Cheng Fu; Hsiao-Yun Huang; Jiun-Huei Jang; Pei-Hsun Huang. River Stage Forecasting Using Multiple Additive Regression Trees. Water Resources Management 2019, 33, 4491 -4507.

AMA Style

Jin-Cheng Fu, Hsiao-Yun Huang, Jiun-Huei Jang, Pei-Hsun Huang. River Stage Forecasting Using Multiple Additive Regression Trees. Water Resources Management. 2019; 33 (13):4491-4507.

Chicago/Turabian Style

Jin-Cheng Fu; Hsiao-Yun Huang; Jiun-Huei Jang; Pei-Hsun Huang. 2019. "River Stage Forecasting Using Multiple Additive Regression Trees." Water Resources Management 33, no. 13: 4491-4507.

Research articles
Published: 28 May 2019 in Urban Water Journal
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Urban flood simulation often ignores or simplifies the function of underground gully systems due to data and computational limitations. To discover the influence of gullies on urban flooding, a novel approach is proposed in this study, by fully-coupling a 1D gully flow model (GFM), a 1D sewer flow model (SFM), and a 2D overland flow model (OFM) to simultaneously simulate the flow exchanges between surface, gullies and sewer pipes. This fully-coupled approach is compared with a simplified approach which directly introduces surface water into sewer pipes without being via gullies. The validation results show that the fully-coupled approach considerably reduces the underestimation of flood extent by 27% compared with the simplified approach. Without considering the capacity of lateral tubes between gullies and sewer pipes, the simplified approach over-drains the surface water into sewer pipes. The modelling of gully flow is crucial for correctly evaluating the efficiency of drainage systems.

ACS Style

Jiun-Huei Jang; Chi-Tai Hsieh; Tien-Hao Chang. The importance of gully flow modelling to urban flood simulation. Urban Water Journal 2019, 16, 377 -388.

AMA Style

Jiun-Huei Jang, Chi-Tai Hsieh, Tien-Hao Chang. The importance of gully flow modelling to urban flood simulation. Urban Water Journal. 2019; 16 (5):377-388.

Chicago/Turabian Style

Jiun-Huei Jang; Chi-Tai Hsieh; Tien-Hao Chang. 2019. "The importance of gully flow modelling to urban flood simulation." Urban Water Journal 16, no. 5: 377-388.

Journal article
Published: 12 July 2018 in Water
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In Taiwan, the coastal hazard from typhoon-induced storm waves poses a greater threat to human life and infrastructure than storm surges. Therefore, there has been increased interest in assessing the storm wave hazard levels for the nearshore waters of Taiwan. This study hindcasted the significant wave heights (SWHs) of 124 historical typhoon events from 1978 to 2017 using a fully coupled model and hybrid wind fields (a combination of the parametric typhoon model and reanalysis products). The maximum SWHs of each typhoon category were extracted to create individual storm wave hazard maps for the sea areas of the coastal zones (SACZs) in Taiwan. Each map was classified into five hazard levels (I to V) and used to generate a comprehensive storm wave hazard map. The results demonstrate that the northern and eastern nearshore waters of Taiwan are threatened by a hazard level IV (SWHs ranging from 9.0 to 12.0 m) over a SACZ of 510.0 km2 and a hazard level V (SWHs exceeding 12.0 m) over a SACZ of 2152.3 km2. The SACZs threatened by hazard levels I (SWHs less than 3.0 m), II (SWHs ranging from 3.0 to 6.0 m), and III (SWHs ranging from 6.0–9.0 m) are of 1045.2 km2, 1793.9 km2, and 616.1 km2, respectively, and are located in the western waters of Taiwan.

ACS Style

Chih-Hsin Chang; Hung-Ju Shih; Wei-Bo Chen; Wen-Ray Su; Lee-Yaw Lin; Yi-Chiang Yu; Jiun-Huei Jang. Hazard Assessment of Typhoon-Driven Storm Waves in the Nearshore Waters of Taiwan. Water 2018, 10, 926 .

AMA Style

Chih-Hsin Chang, Hung-Ju Shih, Wei-Bo Chen, Wen-Ray Su, Lee-Yaw Lin, Yi-Chiang Yu, Jiun-Huei Jang. Hazard Assessment of Typhoon-Driven Storm Waves in the Nearshore Waters of Taiwan. Water. 2018; 10 (7):926.

Chicago/Turabian Style

Chih-Hsin Chang; Hung-Ju Shih; Wei-Bo Chen; Wen-Ray Su; Lee-Yaw Lin; Yi-Chiang Yu; Jiun-Huei Jang. 2018. "Hazard Assessment of Typhoon-Driven Storm Waves in the Nearshore Waters of Taiwan." Water 10, no. 7: 926.

Journal article
Published: 01 July 2018 in Journal of Hydrology
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For a highly developed urban area with complete drainage systems, flood simulation is necessary for describing the flow dynamics from rainfall, to surface runoff, and to sewer flow. In this study, a coupled flood model based on diffusion wave equations was proposed to simulate one-dimensional sewer flow and two-dimensional overland flow simultaneously. The overland flow model provides details on the rainfall-runoff process to estimate the excess runoff that enters the sewer system through street inlets for sewer flow routing. Three types of inlet modelling are considered in this study, including the manhole-based approach that ignores the street inlets by draining surface water directly into manholes, the inlet-manhole approach that drains surface water into manholes that are each connected to multiple inlets, and the inlet-node approach that drains surface water into sewer nodes that are connected to individual inlets. The simulation results were compared with a high-intensity rainstorm event that occurred in 2015 in Taipei City. In the verification of the maximum flood extent, the two approaches that considered street inlets performed considerably better than that without street inlets. When considering the aforementioned models in terms of temporal flood variation, using manholes as receivers leads to an overall inefficient draining of the surface water either by the manhole-based approach or by the inlet-manhole approach. Using the inlet-node approach is more reasonable than using the inlet-manhole approach because the inlet-node approach greatly reduces the fluctuation of the sewer water level. The inlet-node approach is more efficient in draining surface water by reducing flood volume by 13% compared with the inlet-manhole approach and by 41% compared with the manhole-based approach. The results show that inlet modeling has a strong influence on drainage efficiency in coupled flood simulation.

ACS Style

Jiun-Huei Jang; Tien-Hao Chang; Wei-Bo Chen. Effect of inlet modelling on surface drainage in coupled urban flood simulation. Journal of Hydrology 2018, 562, 168 -180.

AMA Style

Jiun-Huei Jang, Tien-Hao Chang, Wei-Bo Chen. Effect of inlet modelling on surface drainage in coupled urban flood simulation. Journal of Hydrology. 2018; 562 ():168-180.

Chicago/Turabian Style

Jiun-Huei Jang; Tien-Hao Chang; Wei-Bo Chen. 2018. "Effect of inlet modelling on surface drainage in coupled urban flood simulation." Journal of Hydrology 562, no. : 168-180.

Journal article
Published: 11 April 2018 in Journal of Hydroinformatics
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Bed topography in river bends is highly non-uniform as a result of the spiral motion of fluid and sediment transports related to channel curvature. To grasp a full understanding of geomorphology and hydrology in natural river bends, detailed bed topography data are necessary, but are usually not of high enough quality and so require further interpolation for sophisticated studies. In this paper, an algorithm is proposed that is particularly suited to bathymetry interpolation in rivers with apparent bends. The thalweg and the two banks are used as geographical features to ensure that a concave cross-sectional bed-form can be found in bend geometry, while linear interpolations are conducted in the in accordance with secondary and main stream currents, respectively. In comparison with conventional spatial interpolation methods, the proposed algorithm is validated to ensure better performance in generating smooth and accurate bed topography in channel bends, which results in better predictions of river stage by 2D hydrodynamic simulation in practical field tests.

ACS Style

Yan Ting Lin; Wei-Bo Chen; Yuan-Fong Su; Jen-Yu Han; Jiun-Huei Jang. Improving river stage forecast by bed reconstruction in sinuous bends. Journal of Hydroinformatics 2018, 20, 960 -974.

AMA Style

Yan Ting Lin, Wei-Bo Chen, Yuan-Fong Su, Jen-Yu Han, Jiun-Huei Jang. Improving river stage forecast by bed reconstruction in sinuous bends. Journal of Hydroinformatics. 2018; 20 (4):960-974.

Chicago/Turabian Style

Yan Ting Lin; Wei-Bo Chen; Yuan-Fong Su; Jen-Yu Han; Jiun-Huei Jang. 2018. "Improving river stage forecast by bed reconstruction in sinuous bends." Journal of Hydroinformatics 20, no. 4: 960-974.

Journal article
Published: 01 April 2018 in Renewable Energy
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ACS Style

Wen-Ray Su; Hongey Chen; Wei-Bo Chen; Chih-Hsin Chang; Lee-Yaw Lin; Jiun-Huei Jang; Yi-Chiang Yu. Numerical investigation of wave energy resources and hotspots in the surrounding waters of Taiwan. Renewable Energy 2018, 118, 814 -824.

AMA Style

Wen-Ray Su, Hongey Chen, Wei-Bo Chen, Chih-Hsin Chang, Lee-Yaw Lin, Jiun-Huei Jang, Yi-Chiang Yu. Numerical investigation of wave energy resources and hotspots in the surrounding waters of Taiwan. Renewable Energy. 2018; 118 ():814-824.

Chicago/Turabian Style

Wen-Ray Su; Hongey Chen; Wei-Bo Chen; Chih-Hsin Chang; Lee-Yaw Lin; Jiun-Huei Jang; Yi-Chiang Yu. 2018. "Numerical investigation of wave energy resources and hotspots in the surrounding waters of Taiwan." Renewable Energy 118, no. : 814-824.

Journal article
Published: 26 January 2018 in Water
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Evaluating land and runoff variations caused by urbanization is crucial to ensure the safety of people living in highly developed areas. Based on spatial scales, runoff analysis involves different methods associated with the interpretation of land cover and land use, the application of hydrological models, and the consideration of flood mitigation measures. Most studies have focused on analyzing the phenomenon on a certain scale by using a single data source and a specific model without discussing mutual influences. In this study, the runoff changes caused by urbanization are assessed and cross-analyzed on three sizes of study areas in the Zhuoshui River Basin in Taiwan, including basin (large), watershed (medium), and city (small) scales. The results demonstrate that, on the basin scale, land-cover changes interpreted from satellite images are very helpful for identifying the watersheds with urbanization hotspots that might have larger runoff outputs. However, on the watershed scale, the resolution of the land-cover data is too low, and land-cover data should be replaced by investigated land-use data for sophisticated hydrological modeling. The mixed usage of land-cover and land-use data is not recommended because large discrepancies occur when determining hydrological parameters for runoff simulation. According to present and future land-use scenarios, the influence of urbanization on runoff is simulated by HEC-1 and SWMM on watershed and city scales, respectively. The results of both models are in agreement and show that runoff peaks will obviously increase as a result of urbanization from 2008 to 2030. For low return periods, the increase in runoff as a result of urbanization is more significant and the city’s contribution to runoff is much larger than its area. Through statistical regression, the watershed runoff simulated by HEC-1 can be perfectly predicted by the city runoff simulated by SWMM in combination with other land/rainfall parameters. On the city scale, the installation of LID satisfactorily reduces the runoff peaks to pre-urbanization levels for low return periods, but the effects of LID are not as positive and are debatable for higher return periods. These findings can be used to realize the applicability and limitations of different approaches for analyzing and mitigating urbanization-induced runoff in the process of constructing a sponge city.

ACS Style

Jin-Cheng Fu; Jiun-Huei Jang; Chun-Mao Huang; Wen-Yen Lin; Chia-Cheng Yeh. Cross-Analysis of Land and Runoff Variations in Response to Urbanization on Basin, Watershed, and City Scales with/without Green Infrastructures. Water 2018, 10, 106 .

AMA Style

Jin-Cheng Fu, Jiun-Huei Jang, Chun-Mao Huang, Wen-Yen Lin, Chia-Cheng Yeh. Cross-Analysis of Land and Runoff Variations in Response to Urbanization on Basin, Watershed, and City Scales with/without Green Infrastructures. Water. 2018; 10 (2):106.

Chicago/Turabian Style

Jin-Cheng Fu; Jiun-Huei Jang; Chun-Mao Huang; Wen-Yen Lin; Chia-Cheng Yeh. 2018. "Cross-Analysis of Land and Runoff Variations in Response to Urbanization on Basin, Watershed, and City Scales with/without Green Infrastructures." Water 10, no. 2: 106.

Journal article
Published: 21 July 2017 in Water
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The storm tide is a combination of the astronomical tide and storm surge, which is the actual sea water level leading to flooding in low-lying coastal areas. A full coupled modeling system (Semi-implicit Eulerian-Lagrangian Finite-Element model coupled with Wind Wave Model II, SELFE-WWM-II) for simulating the interaction of tide, surge and waves based on an unstructured grid is applied to simulate the storm tide and wind waves for the northeastern coast of Taiwan. The coupled model was driven by the astronomical tide and consisted of main eight tidal constituents and the meteorological forcings (air pressure and wind stress) of typhoons. SELFE computes the depth-averaged current and water surface elevation passed to WWM-II, while WWM-II passes the radiation stress to SELFE by solving the wave action equation. Hindcasts of wind waves and storm tides for five typhoon events were developed to validate the coupled model. The detailed comparisons generally show good agreement between the simulations and measurements. The contributions of surge induced by wave and meteorological forcings to the storm tide were investigated for Typhoon Soudelor (2015) at three tide gauge stations. The results reveal that the surge contributed by wave radiation stress was 0.55 m at Suao Port due to the giant offshore wind wave (exceeding 16.0 m) caused by Typhoon Soudelor (2015) and the steep sea-bottom slope. The air pressure resulted in a 0.6 m surge at Hualien Port because of an inverted barometer effect. The wind stress effect was only slightly significant at Keelung Port, contributing 0.22 m to the storm tide. We conclude that wind waves should not be neglected when modeling typhoon-induced storm tides, especially in regions with steep sea-bottom slopes. In addition, accurate tidal and meteorological forces are also required for storm tide modeling.

ACS Style

Wei-Bo Chen; Lee-Yaw Lin; Jiun-Huei Jang; Chih-Hsin Chang. Simulation of Typhoon-Induced Storm Tides and Wind Waves for the Northeastern Coast of Taiwan Using a Tide–Surge–Wave Coupled Model. Water 2017, 9, 549 .

AMA Style

Wei-Bo Chen, Lee-Yaw Lin, Jiun-Huei Jang, Chih-Hsin Chang. Simulation of Typhoon-Induced Storm Tides and Wind Waves for the Northeastern Coast of Taiwan Using a Tide–Surge–Wave Coupled Model. Water. 2017; 9 (7):549.

Chicago/Turabian Style

Wei-Bo Chen; Lee-Yaw Lin; Jiun-Huei Jang; Chih-Hsin Chang. 2017. "Simulation of Typhoon-Induced Storm Tides and Wind Waves for the Northeastern Coast of Taiwan Using a Tide–Surge–Wave Coupled Model." Water 9, no. 7: 549.

Journal article
Published: 03 November 2015 in Water
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Issuing warning information to the public when rainfall exceeds given thresholds is a simple and widely-used method to minimize flood risk; however, this method lacks sophistication when compared with hydrodynamic simulation. In this study, an advanced methodology is proposed to improve the warning effectiveness of the rainfall threshold method for urban areas through deterministic-stochastic modeling, without sacrificing simplicity and efficiency. With regards to flooding mechanisms, rainfall thresholds of different durations are divided into two groups accounting for flooding caused by drainage overload and disastrous runoff, which help in grading the warning level in terms of emergency and severity when the two are observed together. A flood warning is then classified into four levels distinguished by green, yellow, orange, and red lights in ascending order of priority that indicate the required measures, from standby, flood defense, evacuation to rescue, respectively. The proposed methodology is tested according to 22 historical events in the last 10 years for 252 urbanized townships in Taiwan. The results show satisfactory accuracy in predicting the occurrence and timing of flooding, with a logical warning time series for taking progressive measures. For systems with multiple rainfall thresholds already in place, the methodology can be used to ensure better application of rainfall thresholds in urban flood warnings.

ACS Style

Jiun-Huei Jang. An Advanced Method to Apply Multiple Rainfall Thresholds for Urban Flood Warnings. Water 2015, 7, 6056 -6078.

AMA Style

Jiun-Huei Jang. An Advanced Method to Apply Multiple Rainfall Thresholds for Urban Flood Warnings. Water. 2015; 7 (11):6056-6078.

Chicago/Turabian Style

Jiun-Huei Jang. 2015. "An Advanced Method to Apply Multiple Rainfall Thresholds for Urban Flood Warnings." Water 7, no. 11: 6056-6078.

Journal article
Published: 22 April 2015 in Water
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Taiwan usually suffers severe inundation disasters during typhoons and strong rainstorms, and therefore flood mitigation is considered an important issue. To assess the effect of the Yuansantze flood diversion tunnel (YFDT) on flood mitigation at the upstream reaches of the Keelung River, a three-dimensional, unstructured grid, Finite-Volume, primitive equation Community Ocean Model (FVCOM) was used. The model was validated with observed data for water levels and inundation extent during different typhoon events. The simulated results show a good agreement with field measurements of water level with three historical typhoon events but underestimated the measured inundation extent with Typhoon Nari. The validated model was then applied to assess the flood mitigation and economic loss with the YFDT. The results demonstrated that the river level decreases approximately 3 m with the YFDT and that the inundation extent decreases by more than 50% in the Ruifang District with YFDT. The YDFT aims to not only mitigate hazards but also reduce economic losses. The average annual expected benefit after construction of the YFDT is approximately 184 million NTD in the Ruifang District.

ACS Style

Wei-Bo Chen; Wen-Cheng Liu; Huei-Shuin Fu; Jiun-Huei Jang. Assessing the Influences of a Flood Diversion Project on Mitigating River Stage, Inundation Extent and Economic Loss. Water 2015, 7, 1731 -1750.

AMA Style

Wei-Bo Chen, Wen-Cheng Liu, Huei-Shuin Fu, Jiun-Huei Jang. Assessing the Influences of a Flood Diversion Project on Mitigating River Stage, Inundation Extent and Economic Loss. Water. 2015; 7 (12):1731-1750.

Chicago/Turabian Style

Wei-Bo Chen; Wen-Cheng Liu; Huei-Shuin Fu; Jiun-Huei Jang. 2015. "Assessing the Influences of a Flood Diversion Project on Mitigating River Stage, Inundation Extent and Economic Loss." Water 7, no. 12: 1731-1750.

Articles
Published: 15 April 2013 in Journal of the Chinese Institute of Engineers
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After the catastrophic disaster brought by Typhoon Morakot in 2009, the enhancement of flood warning technology cannot wait in Taiwan. In recent years, ensemble flood warning has exhibited advantages in extending lead time, quantifying uncertainty and raising confidence in issuing warnings. Unlike most ensembles aimed at integrating meteorological variations, this study generates the ensemble through the combination of multiple conceptually different hydrological models in order to avoid possible bias by applying a single model for a flood forecast. Taking Typhoon Morakot as the study case, the townships in Chiayi City/County are selected as the study areas to compare the performance of ensemble warning with that given by individual models. The results indicate that the ensemble warning shows better accuracy than individual models by giving higher overall correctness, revealing the fact that hydrological ensemble is no less important than meteorological ensemble in acquiring better flood warning performance.

ACS Style

Pao-Shan Yu; Ming-Hsi Hsu; Jiun-Huei Jang; Jin-Cheng Fu; Chen-Jia Huang; Sen-Hai Yeh. Flood warning by ensemble of multiple hydrological models: a case study for Typhoon Morakot. Journal of the Chinese Institute of Engineers 2013, 37, 570 -581.

AMA Style

Pao-Shan Yu, Ming-Hsi Hsu, Jiun-Huei Jang, Jin-Cheng Fu, Chen-Jia Huang, Sen-Hai Yeh. Flood warning by ensemble of multiple hydrological models: a case study for Typhoon Morakot. Journal of the Chinese Institute of Engineers. 2013; 37 (5):570-581.

Chicago/Turabian Style

Pao-Shan Yu; Ming-Hsi Hsu; Jiun-Huei Jang; Jin-Cheng Fu; Chen-Jia Huang; Sen-Hai Yeh. 2013. "Flood warning by ensemble of multiple hydrological models: a case study for Typhoon Morakot." Journal of the Chinese Institute of Engineers 37, no. 5: 570-581.

Journal article
Published: 01 September 2011 in Journal of Hydraulic Engineering
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In bed-load sediment transport, the lifting force plays an important role in reducing the friction between sediment particles and the bed surface, and it makes particle transportation by the shear force easier. Because the lifting force is related to vorticity, a three-dimensional (3D) numerical model incorporating large eddy simulations was applied to simulate the vorticity field in a channel bend. The results show that the distribution of vorticity is highly nonuniform, and it can lead to significant variations in lifting force and bed-load sediment transport per unit width in a channel bend. Relevant theories are modified on the basis of physical reasoning and then incorporated into numerical models to investigate the lifting-force effects on the bed topography and bed-surface sediment size gradation in a channel bend. With the lifting-force effects considered, it is shown that the errors in simulated bed topography can be reduced by approximately 40% and in bed-surface sediment size by 50%.

ACS Style

Jiun-Huei Jang; Hsin-Ya Ho; Chin-Lien Yen. Effects of Lifting Force on Bed Topography and Bed-Surface Sediment Size in Channel Bend. Journal of Hydraulic Engineering 2011, 137, 911 -920.

AMA Style

Jiun-Huei Jang, Hsin-Ya Ho, Chin-Lien Yen. Effects of Lifting Force on Bed Topography and Bed-Surface Sediment Size in Channel Bend. Journal of Hydraulic Engineering. 2011; 137 (9):911-920.

Chicago/Turabian Style

Jiun-Huei Jang; Hsin-Ya Ho; Chin-Lien Yen. 2011. "Effects of Lifting Force on Bed Topography and Bed-Surface Sediment Size in Channel Bend." Journal of Hydraulic Engineering 137, no. 9: 911-920.

Journal article
Published: 20 July 2011 in Hydrological Processes
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Deterministic flood inundation mapping is valuable for the investigation of detailed flood depth and extent. However, when these data are used for real‐time flood warning, uncertainty arises while encountering the difficulties of timely response, message interpretation and performance evaluation that makes statistical analysis necessary. By incorporating deterministic flood inundation map outputs statistically by means of logistic regression, this paper presents a probabilistic real‐time flood warning model determining region‐based flood probability directly from rainfall, being efficient in computation, clear in message, and valid in physical meaning. The calibration and validation of the probabilistic model show a satisfactory overall correctness rate, with the hit rate far surpassing the false alarm rate in issuing flood warning for historical events. Further analyses show that the probabilistic model is effective in evaluating the level of uncertainty lying within flood warning which can be reduced by several techniques proposed in order to improve warning performance. Copyright © 2011 John Wiley & Sons, Ltd.

ACS Style

Jiun-Huei Jang; Pao-Shan Yu; Sen-Hai Yeh; Jin-Cheng Fu; Chen-Jia Huang. A probabilistic model for real-time flood warning based on deterministic flood inundation mapping. Hydrological Processes 2011, 26, 1079 -1089.

AMA Style

Jiun-Huei Jang, Pao-Shan Yu, Sen-Hai Yeh, Jin-Cheng Fu, Chen-Jia Huang. A probabilistic model for real-time flood warning based on deterministic flood inundation mapping. Hydrological Processes. 2011; 26 (7):1079-1089.

Chicago/Turabian Style

Jiun-Huei Jang; Pao-Shan Yu; Sen-Hai Yeh; Jin-Cheng Fu; Chen-Jia Huang. 2011. "A probabilistic model for real-time flood warning based on deterministic flood inundation mapping." Hydrological Processes 26, no. 7: 1079-1089.

Journal article
Published: 01 June 2010 in Journal of Disaster Research
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Typhoon Morakot hit Taiwan during August 7-9, 2009. Its record-breaking rainfall caused catastrophic damage, making it the deadliest typhoon to visit Taiwan in the last 50 years. Conducting a three-months and 160-member-strong field investigation of the scale and causes of this disaster, this paper proposes strategies effective to improve flood prevention work in Taiwan. The severe flood disaster triggered by Typhoon Morakot’s excessive rainfall is attributable to four factors: (1) hydraulic system failures, (2) river flow retardation, (3) reservoir release, and (4) land subsidence. Based on these findings, this paper proposes comprehensive improvement strategies in hydraulic facility inspection, emergency response, river basin management, and climate change assessment to improve flood prevention work in Taiwan. This study combines governmental, academic, and public efforts in investigating effective post-disaster flood prevention strategies that we hope will prove to be a useful reference for other countries while facing such issues.

ACS Style

Lung-Sheng Hsieh; Jiun-Huei Jang; Hsuan-Ju Lin; Pao-Shan Yu. Flood Prevention Strategy in Taiwan: Lessons Learned from Typhoon Morakot. Journal of Disaster Research 2010, 5, 325 -329.

AMA Style

Lung-Sheng Hsieh, Jiun-Huei Jang, Hsuan-Ju Lin, Pao-Shan Yu. Flood Prevention Strategy in Taiwan: Lessons Learned from Typhoon Morakot. Journal of Disaster Research. 2010; 5 (3):325-329.

Chicago/Turabian Style

Lung-Sheng Hsieh; Jiun-Huei Jang; Hsuan-Ju Lin; Pao-Shan Yu. 2010. "Flood Prevention Strategy in Taiwan: Lessons Learned from Typhoon Morakot." Journal of Disaster Research 5, no. 3: 325-329.

Full paper
Published: 01 June 2006 in Journal of the Chinese Institute of Engineers
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A 3D‐numerical model based on large eddy simulation and a wall model has been applied to simulate the flow field and bed shear stress in a channel bend. As the bed‐surface sediment distribution is related to the shear force and lifting force near the bed, a method for calculation of the lifting force experienced by a sediment particle in a channel bend has been introduced. With some assumptions and deductions, the bed‐surface sediment size distribution can be described as a function composed of shear force and lifting force in this study. By comparing with the experimental data, the function reveals that, with the effect of lifting force considered, the accuracy in predicting the bed‐surface sediment size distribution can be improved by up to 41% in the transverse direction and 46% in the longitudinal direction.

ACS Style

Jiun‐Huei Jang; Hsin‐Ya Ho; Chin‐Lien Yen. Effect of lift on bed?surface sediment size distribution in channel bend. Journal of the Chinese Institute of Engineers 2006, 29, 565 -579.

AMA Style

Jiun‐Huei Jang, Hsin‐Ya Ho, Chin‐Lien Yen. Effect of lift on bed?surface sediment size distribution in channel bend. Journal of the Chinese Institute of Engineers. 2006; 29 (4):565-579.

Chicago/Turabian Style

Jiun‐Huei Jang; Hsin‐Ya Ho; Chin‐Lien Yen. 2006. "Effect of lift on bed?surface sediment size distribution in channel bend." Journal of the Chinese Institute of Engineers 29, no. 4: 565-579.