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Prof. Wen-Cheng Liu
Department of Civil and Disaster Prevention Engineering, National United University, Miao-li 360001, Taiwan

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Danshuei River Estuary
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Shihmen Reservoir

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Short Biography

Wen-Cheng Liu received B.Sc., M.Eng., and Ph.D. degrees from National Taiwan University, Taiwan, in 1986, 1989, and 1999, respectively. Now, he is a distinguished professor and vice-president of National United University. He is a president of Taiwan Group on Earth Observations (TGEO).

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Journal article
Published: 06 July 2021 in Remote Sensing
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The accuracy of river velocity measurements plays an important role in the effective management of water resources. Various methods have been developed to measure river velocity. Currently, image-based techniques provide a promising approach to avoid physical contact with targeted water bodies by researchers. In this study, measured surface velocities collected under low flow and high flow conditions in the Houlong River, Taiwan, using large-scale particle image velocimetry (LSPIV) captured by an unmanned aerial vehicle (UAV) and a terrestrial fixed station were analyzed and compared. Under low flow conditions, the mean absolute errors of the measured surface velocities using LSPIV from a UAV with shooting heights of 9, 12, and 15 m fell within 0.055 ± 0.015 m/s, which was lower than that obtained using LSPIV on video recorded from a terrestrial fixed station (i.e., 0.34 m/s). The mean absolute errors obtained using LSPIV derived from UAV aerial photography at a flight height of 12 m without seeding particles and with different seeding particle densities were slightly different, and fell within the range of 0.095 ± 0.025 m/s. Under high flow conditions, the mean absolute errors associated with using LSPIV derived from terrestrial fixed photography and LSPIV derived from a UAV with flight heights of 32, 62, and 112 m were 0.46 m/s and 0.49 m/s, 0.27 m, and 0.97 m/s, respectively. A UAV flight height of 62 m yielded the best measured surface velocity result. Moreover, we also demonstrated that the optimal appropriate interrogation area and image acquisition time interval using LSPIV with a UAV were 16 × 16 pixels and 1/8 s, respectively. These two parameters should be carefully adopted to accurately measure the surface velocity of rivers.

ACS Style

Wen-Cheng Liu; Chien-Hsing Lu; Wei-Che Huang. Large-Scale Particle Image Velocimetry to Measure Streamflow from Videos Recorded from Unmanned Aerial Vehicle and Fixed Imaging System. Remote Sensing 2021, 13, 2661 .

AMA Style

Wen-Cheng Liu, Chien-Hsing Lu, Wei-Che Huang. Large-Scale Particle Image Velocimetry to Measure Streamflow from Videos Recorded from Unmanned Aerial Vehicle and Fixed Imaging System. Remote Sensing. 2021; 13 (14):2661.

Chicago/Turabian Style

Wen-Cheng Liu; Chien-Hsing Lu; Wei-Che Huang. 2021. "Large-Scale Particle Image Velocimetry to Measure Streamflow from Videos Recorded from Unmanned Aerial Vehicle and Fixed Imaging System." Remote Sensing 13, no. 14: 2661.

Journal article
Published: 19 June 2021 in Computers & Geosciences
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A three-axis accelerometer was combined with large-scale particle image velocimetry (LSPIV) to obtain nonintrusive and safe surface velocity measurements. Dual cameras were established at the Yu-Feng gauging station of Shimen Reservoir to capture near-field and far-field images and analyze the surface velocity of rivers. Surface velocity measurements were obtained with a flow meter, LPSIV with ground control points, and LSPIV with a three-axis accelerometer to compare the measurement accuracy. The results show that the relative root mean square error (RMSE) values for LSPIV with ground control points and with the three-axis accelerometer are 21% and 18%, respectively. The LSPIV technique with the three-axis accelerometer slightly improved the measurement accuracy of the surface velocity. However a three-axis accelerometer can be utilized to replace the traditional ground control points for yielding the camera pose parameters. Furthermore, the effects of the camera pose, three-axis acceleration, interrogation area (IA), and image resolution on surface velocity measurements were explored. The camera pose parameters, namely, roll (θ) and tilt (τ), and three-axis acceleration parameters, including Xa and Ya, influence surface velocity measurements. If the measurement error of the surface velocity is controlled within ±10%, the acceptable variational ranges of θ, τ, Xa, and Ya are 6.2°, 1.3°, 0.11 g, and 0.02 g, respectively. The IA size and image resolution also significantly affect the accuracy of surface velocity measurements. Therefore, the selection of a suitable IA size and image resolution is crucial for accurately measuring surface velocity.

ACS Style

Wen-Cheng Liu; Wei-Che Huang. Development of a three-axis accelerometer and large-scale particle image velocimetry (LSPIV) to enhance surface velocity measurements in rivers. Computers & Geosciences 2021, 155, 104866 .

AMA Style

Wen-Cheng Liu, Wei-Che Huang. Development of a three-axis accelerometer and large-scale particle image velocimetry (LSPIV) to enhance surface velocity measurements in rivers. Computers & Geosciences. 2021; 155 ():104866.

Chicago/Turabian Style

Wen-Cheng Liu; Wei-Che Huang. 2021. "Development of a three-axis accelerometer and large-scale particle image velocimetry (LSPIV) to enhance surface velocity measurements in rivers." Computers & Geosciences 155, no. : 104866.

Journal article
Published: 28 April 2021 in Journal of Geophysical Research: Biogeosciences
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Thermal stratification is a critical physical process controlling carbon (C) flux from lakes into the atmosphere. In general, vertical water temperature profiles in shallow subtropical lakes can vary significantly because typhoons frequently induce vertical mixing across the entire lake due to strong winds and rapid flushing from river inputs. Since C fluxes are driven by dissolved inorganic C (DIC), it is necessary to understand stratification's influence on DIC dynamics in shallow subtropical lakes. Therefore, we aimed to clarify the impact of stratification on DIC in Yuan‐Yong Lake, a typical shallow subtropical mountain lake, by developing a Net Ecosystem Production (NEP) model. We measured the vertical profile of water temperature and DIC once or twice a month from July 2004 to December 2017. We applied a three‐dimensional hydrological model to estimate residence time and NEP, which revealed that large amounts of DIC are stored in the lower layer from spring to summer due to the suppression of vertical mixing by stratification. In autumn and winter, the lake was well mixed, and DIC was evenly distributed in the water column due to vertical mixing. This was confirmed by vertical DIC profiles.

ACS Style

Hao‐Chi Lin; Chih‐Yu Chiu; Jeng‐Wei Tsai; Wen‐Cheng Liu; Kazufumi Tada; Keisuke Nakayama. Influence of Thermal Stratification on Seasonal Net Ecosystem Production and Dissolved Inorganic Carbon in a Shallow Subtropical Lake. Journal of Geophysical Research: Biogeosciences 2021, 126, 1 .

AMA Style

Hao‐Chi Lin, Chih‐Yu Chiu, Jeng‐Wei Tsai, Wen‐Cheng Liu, Kazufumi Tada, Keisuke Nakayama. Influence of Thermal Stratification on Seasonal Net Ecosystem Production and Dissolved Inorganic Carbon in a Shallow Subtropical Lake. Journal of Geophysical Research: Biogeosciences. 2021; 126 (4):1.

Chicago/Turabian Style

Hao‐Chi Lin; Chih‐Yu Chiu; Jeng‐Wei Tsai; Wen‐Cheng Liu; Kazufumi Tada; Keisuke Nakayama. 2021. "Influence of Thermal Stratification on Seasonal Net Ecosystem Production and Dissolved Inorganic Carbon in a Shallow Subtropical Lake." Journal of Geophysical Research: Biogeosciences 126, no. 4: 1.

Journal article
Published: 14 March 2021 in Sustainability
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A flood risk assessment of urban areas in Kaohsiung city along the Dianbao River was performed based on flood hazards and social vulnerability. In terms of hazard analysis, a rainfall-runoff model (HEC-HMS) was adopted to simulate discharges in the watershed, and the simulated discharges were utilized as inputs for the inundation model (FLO-2D). Comparisons between the observed and simulated discharges at the Wulilin Bridge flow station during Typhoon Kongrey (2013) and Typhoon Megi (2016) were used for the HEC-HMS model calibration and validation, respectively. The observed water levels at the Changrun Bridge station during Typhoon Kongrey and Typhoon Megi were utilized for the FLO-2D model calibration and validation, respectively. The results indicated that the simulated discharges and water levels reasonably reproduced the observations. The validated model was then applied to predict the inundation depths and extents under 50-, 100-, and 200-year rainfall return periods to form hazard maps. For social vulnerability, the fuzzy Delphi method and the analytic hierarchy process were employed to select the main factors affecting social vulnerability and to yield the weight of each social vulnerability factor. Subsequently, a social vulnerability map was built. A risk map was developed that compiled both flood hazards and social vulnerability levels. Based on the risk map, flood mitigation strategies with structural and nonstructural measures were proposed for consideration by decision-makers.

ACS Style

Wen-Cheng Liu; Tien-Hsiang Hsieh; Hong-Ming Liu. Flood Risk Assessment in Urban Areas of Southern Taiwan. Sustainability 2021, 13, 3180 .

AMA Style

Wen-Cheng Liu, Tien-Hsiang Hsieh, Hong-Ming Liu. Flood Risk Assessment in Urban Areas of Southern Taiwan. Sustainability. 2021; 13 (6):3180.

Chicago/Turabian Style

Wen-Cheng Liu; Tien-Hsiang Hsieh; Hong-Ming Liu. 2021. "Flood Risk Assessment in Urban Areas of Southern Taiwan." Sustainability 13, no. 6: 3180.

Original paper
Published: 04 March 2021 in Natural Hazards
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This study mainly aims to hindcast historical Typhoon Nepartak (2016) and to analyze tide–surge and wave interactions. To achieve this goal, a coupled tide–surge–wave model was built around the coast of Taiwan, and it was applied to simulate storm surges and waves during historical typhoon event. To demonstrate its capability, the coupled model was validated with observed water levels, wind speeds, atmospheric pressures, wave heights, and wave periods at different stations. Quantitatively, the model results reasonably reproduced the observed data. Furthermore, the model was utilized to explore the tide, surge, and wave interaction using historical Typhoon Nepartak (2016). The model results revealed that onshore wind enhanced the surge height, while offshore wind decreased the surge height. The atmospheric pressure consistently displayed a positive contribution to surge height. The wind-induced surge height contributing to the total surge height was 136.83% at Taichung Harbor, because the offshore wind mainly dominated the surge height compared to the effect of atmospheric pressure. The atmospheric pressure-induced surge heights contributing to the total surge height were 100.59%, 96.26%, and 99.74% at Kaohsiung Harbor, Hualien Harbor, and Taitung Fugang, respectively, as a result of the atmospheric pressure dominating the surge height. However, the contribution of the wave setup to the total surge height was minor. The path of typhoons at different time frames significantly affected the spatial distributions of surge height and wave height around the coast of Taiwan. The contributions of water level and current to wave height reached a maximum value of approximately 0.3 m at Suao, while the contributions at Penghu, Qigu, and Eluanbi were all less than 0.2 m. This signified that the influence of the water level and current on wave height was not negligible.

ACS Style

Wen-Cheng Liu; Wei-Che Huang. Tide–surge and wave interaction around the Taiwan coast: insight from Typhoon Nepartak in 2016. Natural Hazards 2021, 1 -24.

AMA Style

Wen-Cheng Liu, Wei-Che Huang. Tide–surge and wave interaction around the Taiwan coast: insight from Typhoon Nepartak in 2016. Natural Hazards. 2021; ():1-24.

Chicago/Turabian Style

Wen-Cheng Liu; Wei-Che Huang. 2021. "Tide–surge and wave interaction around the Taiwan coast: insight from Typhoon Nepartak in 2016." Natural Hazards , no. : 1-24.

Journal article
Published: 26 August 2020 in Water
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Storm surge induced by severe typhoons has caused many catastrophic tragedies to coastal communities over past decades. Accurate and efficient prediction/assessment of storm surge is still an important task in order to achieve coastal disaster mitigation especially under the influence of climate change. This study revisits storm surge predictions using artificial neural networks (ANN) and effective typhoon parameters. Recent progress of storm surge modeling and some remaining unresolved issues are reviewed. In this paper, we chose the northeastern region of Taiwan as the study area, where the largest storm surge record (over 1.8 m) has been observed. To develop the ANN-based storm surge model for various lead-times (from 1 to 12 h), typhoon parameters are carefully examined and selected by analogy with the physical modeling approach. A knowledge extraction method (KEM) with backward tracking and forward exploration procedures is also proposed to analyze the roles of hidden neurons and typhoon parameters in storm surge prediction, as well as to reveal the abundant, useful information covered in the fully-trained artificial brain. Finally, the capability of ANN model for long-lead-time predictions and influences in controlling parameters are investigated. Overall, excellent agreement with observations (i.e., the coefficient of efficiency CE > 0.95 for training and CE > 0.90 for validation) is achieved in one-hour-ahead prediction. When the typhoon affects coastal waters, contributions of wind speed, central pressure deficit, and relative angle are clarified via influential hidden neurons. A general pattern of maximum storm surge under various scenarios is also obtained. Moreover, satisfactory accuracy is successfully extended to a much longer lead time (i.e., CE > 0.85 for training and CE > 0.75 for validation in 12-h-ahead prediction). Possible reasons for further accuracy improvement compared to earlier works are addressed.

ACS Style

Wei-Ting Chao; Chih-Chieh Young; Tai-Wen Hsu; Wen-Cheng Liu; Chian-Yi Liu. Long-Lead-Time Prediction of Storm Surge Using Artificial Neural Networks and Effective Typhoon Parameters: Revisit and Deeper Insight. Water 2020, 12, 2394 .

AMA Style

Wei-Ting Chao, Chih-Chieh Young, Tai-Wen Hsu, Wen-Cheng Liu, Chian-Yi Liu. Long-Lead-Time Prediction of Storm Surge Using Artificial Neural Networks and Effective Typhoon Parameters: Revisit and Deeper Insight. Water. 2020; 12 (9):2394.

Chicago/Turabian Style

Wei-Ting Chao; Chih-Chieh Young; Tai-Wen Hsu; Wen-Cheng Liu; Chian-Yi Liu. 2020. "Long-Lead-Time Prediction of Storm Surge Using Artificial Neural Networks and Effective Typhoon Parameters: Revisit and Deeper Insight." Water 12, no. 9: 2394.

Journal article
Published: 12 April 2020 in Water
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Anthropogenic changes in tidal estuaries have significantly altered bathymetry and topography over the past half century. The geomorphic-driven changes in estuarine hydrodynamics and salt transport remain unclear. To explore this issue, a SELFE (Semi-implicit Eulaerian-Lagrangian Finite Element) -based model was developed and utilized in a case study in the Danshui River, Taiwan. The model was calibrated and validated using observed water level, current, and salinity data from 2015, 2016, and 2017. The performance of the SELFE model corresponded well to the measured data. Furthermore, the validated model was utilized to analyze the hydrodynamics, residual current, limit of salt intrusion, and residence time under the predevelopment (1981) and present (2015) conditions. The predicted results revealed that the time lag of water surface elevation at both high tide and low tide under the present condition was approximately 0.5–2 h shorter under the predevelopment condition. The residual circulation under the predevelopment condition was stronger than under the present condition for low flow, causing the limit of salt intrusion to extend further upstream under the predevelopment condition compared to the limit of salt intrusion under the present condition. The calculated residence time under the predevelopment condition was longer than the residence time under the present condition. The freshwater discharge input is a dominating factor affecting the salt intrusion and residence time in a tidal estuary. A regression correlation between the maximum distance of salt intrusion and freshwater discharge and a correlation between residence time and freshwater discharge were established to predict the limit of salt intrusion and residence time under the predevelopment and present conditions with different scenarios of freshwater discharge input.

ACS Style

Wen-Cheng Liu; Min-Hsin Ke; Hong-Ming Liu. Response of Salt Transport and Residence Time to Geomorphologic Changes in an Estuarine System. Water 2020, 12, 1091 .

AMA Style

Wen-Cheng Liu, Min-Hsin Ke, Hong-Ming Liu. Response of Salt Transport and Residence Time to Geomorphologic Changes in an Estuarine System. Water. 2020; 12 (4):1091.

Chicago/Turabian Style

Wen-Cheng Liu; Min-Hsin Ke; Hong-Ming Liu. 2020. "Response of Salt Transport and Residence Time to Geomorphologic Changes in an Estuarine System." Water 12, no. 4: 1091.

Review
Published: 29 March 2020 in Sustainability
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Water is a limited resource but essential to sustaining life and supporting economic development. Only 2.5% of all the water on Earth is freshwater and can be used to meet basic human needs such as a clean supply of water for drinking, cooking, and bathing. Water scarcity is the result of an imbalance between supply and demand. Efficient water resource management is definitely of interest to research and is a practical topic. At the same time, water-related disasters such as floods and droughts cause the loss of life and property. Disasters increase the difficulty of effective water resource management. An increase in climate extremes can also increase the risk of floods and droughts. This overview covers 150 peer-reviewed journal publications from the last twenty years focusing on risk-reduction strategies for floods and droughts. First, a definition and classification of flood and drought was introduced. Second, studies and techniques associated with risk reduction were grouped into three themes and discussed: prediction and warning; monitoring; and impact assessment, response, and management. As a result, many studies were solely focused on, and achieve excellence in, their own themes. Special attention was needed to find in these studies what can convert the adverse impacts such as flood water to positive outcomes such as drought relief. Multidisciplinary cooperation is necessary to achieve sustainability and to adapt to climate change. Finally, advanced techniques such as artificial intelligence (AI) and the internet of things (IoT) were foreseen to have a tremendous impact on future disaster risk reduction.

ACS Style

Tsun-Hua Yang; Wen-Cheng Liu. A General Overview of the Risk-Reduction Strategies for Floods and Droughts. Sustainability 2020, 12, 2687 .

AMA Style

Tsun-Hua Yang, Wen-Cheng Liu. A General Overview of the Risk-Reduction Strategies for Floods and Droughts. Sustainability. 2020; 12 (7):2687.

Chicago/Turabian Style

Tsun-Hua Yang; Wen-Cheng Liu. 2020. "A General Overview of the Risk-Reduction Strategies for Floods and Droughts." Sustainability 12, no. 7: 2687.

Preprint content
Published: 23 March 2020
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In this research, we conducted LSPIV (Large Scale Particle Image Velocimetry) measurements to measure river surface velocity based on images recorded by mobile phone. The realization of this research is based on the developments of two products. The first one is the digital camera, which has been combined with the mobile phone after several years of development. The second one is the three-axis accelerometer, which can measure the attitude of the object. A three-axis accelerometer is one of the necessary parts of the mobile phone nowadays, as many functions of the mobile phone, such as step counting, Do Not Disturb mode, games, require the detection of attitude.

In LSPIV, there are nine parameters of the collinear equation. Three of parameters are the coordinates of the perspective center in the image space (focus distance d and image center position (u, v)), which can be determined in advance in the laboratory; the other three parameters are the coordinates (x, y, z) of the perspective center in real space, which can be set to (0, 0, 0); the last three parameters are the attitude of the camera (i.e., the mobile phone), which is determined by the depression angle, the horizontal angle, and the left-right rotation angle and can be measured by three-axis accelerometer. Therefore, river surface velocity could be analyzed by LSPIV with not only continuous images captured by a camera of the mobile phone but also the acceleration values obtained by the three-axis accelerometer when each image was captured.

In the present study, Yufeng gauging station, which is in the upstream catchment of the Shihmen Reservoir in Taiwan, is selected as the study site. Two other measurement methods were used to measure the river surface velocity and the comparison was conducted. One is using a handheld digital flow meter and another is using LSPIV with control points to calculate the parameters for measuring the river surface velocity.

ACS Style

Wen-Cheng Liu; Wei-Che Huang. Large scale particle image velocimetry measurement of river surface velocity based on images captured by a camera of the mobile phone. 2020, 1 .

AMA Style

Wen-Cheng Liu, Wei-Che Huang. Large scale particle image velocimetry measurement of river surface velocity based on images captured by a camera of the mobile phone. . 2020; ():1.

Chicago/Turabian Style

Wen-Cheng Liu; Wei-Che Huang. 2020. "Large scale particle image velocimetry measurement of river surface velocity based on images captured by a camera of the mobile phone." , no. : 1.

Journal article
Published: 04 February 2020 in Science of The Total Environment
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Lentic ecosystems are important agents of local and global carbon cycling, but their contribution varies along gradients of dissolved organic matter (DOM) and productivity. We investigated how contrasting summer and autumn precipitation can shape annual and inter-annual variation in ecosystem carbon (C) flux (gross primary production (GPP), ecosystem respiration (ER), and CO2 efflux) in two subtropical lakes differing substantially in trophic state and water color. Instrumented buoys recorded time series of free-water DO, terrestrial DOM (tDOM), chlorophyll a, water temperature profiles, and meteorological measurements over five years (2009–2011 and 2014–2015). Reduced precipitation caused immediate and prolonged effects on C flux in both lakes. During the drought year (2014) GPP and ER declined by 60 to 80% and both lakes were either CO2 sinks or neutral. In the subsequent wet year (2015), GPP and ER increased by 40 to 110%, and both lakes shifted to strong net CO2 emitters. Higher ecosystem R resulted from larger GPP while higher tDOM contributed to a dramatic increase in dissolved inorganic carbon, which intensified CO2 emission in both lakes. C flux was more responsive in the clear mesotrophic lake, declining by approximately 40% in the cumulative GPP and ER, and increasing by >400% in CO2 efflux whereas changes in the oligotrophic colored lake were more modest (approximately 30% and 300% for metabolic declines and efflux increases, respectively). Temporal variation and magnitude of C flux were governed by tDOM-mediated changes in epilimnetic nutrient levels and hypolimnetic light availability. This study demonstrated terrestrial loads of DOM strongly influence the inter-annual response and sensitivity of ecosystem C flux to variation in inter-annual precipitation. Our findings have important implications for predicting the trend, magnitude, duration, and sensitivity of the response of C flux in subtropical lakes/reservoirs to future changes in precipitation patterns under altered climatic conditions.

ACS Style

Chih-Yu Chiu; John R. Jones; James A. Rusak; Hao-Chi Lin; Keisuke Nakayama; Timothy K. Kratz; Wen-Cheng Liu; Sen-Lin Tang; Jeng-Wei Tsai. Terrestrial loads of dissolved organic matter drive inter-annual carbon flux in subtropical lakes during times of drought. Science of The Total Environment 2020, 717, 137052 .

AMA Style

Chih-Yu Chiu, John R. Jones, James A. Rusak, Hao-Chi Lin, Keisuke Nakayama, Timothy K. Kratz, Wen-Cheng Liu, Sen-Lin Tang, Jeng-Wei Tsai. Terrestrial loads of dissolved organic matter drive inter-annual carbon flux in subtropical lakes during times of drought. Science of The Total Environment. 2020; 717 ():137052.

Chicago/Turabian Style

Chih-Yu Chiu; John R. Jones; James A. Rusak; Hao-Chi Lin; Keisuke Nakayama; Timothy K. Kratz; Wen-Cheng Liu; Sen-Lin Tang; Jeng-Wei Tsai. 2020. "Terrestrial loads of dissolved organic matter drive inter-annual carbon flux in subtropical lakes during times of drought." Science of The Total Environment 717, no. : 137052.

Review
Published: 10 December 2019 in Environmental Monitoring and Assessment
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A three-dimensional contaminant transport model of heavy metal (copper) was coupled with the hydrodynamics and suspended sediment transport module to simulate the transport and distribution of heavy metal (copper) of the Danshui River estuarine system in northern Taiwan. The coupled model was validated with observational data including the water level, tidal current, salinity, suspended sediment concentration, and copper concentration. The model simulation results quantitatively reproduce the measurements. Furthermore, the validated model was employed to explore the influences of the freshwater discharge and suspended sediment on the distribution of copper concentrations in the tidal estuarine system. The results demonstrate that a high freshwater discharge results in a decreasing copper concentration, while a low freshwater discharge raises the copper concentration along the estuarine system. If the suspended sediment transport module was excluded in the model simulations, the predicted copper concentration underestimated the measured data. The distribution of copper concentrations without the suspended sediment transport module was lower than that with the suspended sediment transport module. The simulated results indicate that the freshwater discharge and suspended sediment play crucial roles in affecting the distribution of copper concentrations in the tidal estuarine system.

ACS Style

Wen-Cheng Liu; Hong-Ming Liu; Poi-Jiu Ken. Investigating the contaminant transport of heavy metals in estuarine waters. Environmental Monitoring and Assessment 2019, 192, 31 .

AMA Style

Wen-Cheng Liu, Hong-Ming Liu, Poi-Jiu Ken. Investigating the contaminant transport of heavy metals in estuarine waters. Environmental Monitoring and Assessment. 2019; 192 (1):31.

Chicago/Turabian Style

Wen-Cheng Liu; Hong-Ming Liu; Poi-Jiu Ken. 2019. "Investigating the contaminant transport of heavy metals in estuarine waters." Environmental Monitoring and Assessment 192, no. 1: 31.

Research article
Published: 04 December 2019 in Environmental Science and Pollution Research
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Based on the observed heavy metals in the Danshui River estuarine system, the concentration of manganese (Mn) exceeds the water quality standards. High concentrations of manganese in aquatic environment can cause disturbances in the sodium balance, disturb the metabolism of carbohydrates, and impair the immunological functions of fish. Therefore, a three-dimensional heavy metal transport model was developed and incorporated into the hydrodynamics, salinity, and suspended sediment transport model to evaluate the concentration distribution of the heavy metal manganese (Mn) in the Danshui River estuarine system of northern Taiwan. The model was validated with observational data for water level, tidal current, salinity, suspended sediment concentration, and heavy metal (Mn) concentration that was measured in 2015. The indicators of statistical error, including mean absolute error (MAE), root mean square error (RMSE), and skill score (SS), were adopted to evaluate the model performance. There was good quantitative agreement between the simulation results and measurements. Sensitivity analysis of suspended sediment and heavy metal transport model was carried out to understand which parameters were important to be cautiously determined. Furthermore, the validated model was used to investigate the influence of suspended sediment on the concentration distribution of heavy metals (Mn) in tidal estuaries. If the suspended sediment transport module was excluded in model simulations, the predicted results for the heavy metal (Mn) concentration underestimated the measured data. The modeling results showed that the inclusion of the suspended sediment transport module in the model simulations was critically important to the results of the heavy metal (Mn) concentration in the tidal estuarine system in Taiwan.

ACS Style

Wen-Cheng Liu; Poi-Jiu Ken; Hong-Ming Liu. Transport and distribution of manganese in tidal estuarine system in Taiwan. Environmental Science and Pollution Research 2019, 27, 510 -531.

AMA Style

Wen-Cheng Liu, Poi-Jiu Ken, Hong-Ming Liu. Transport and distribution of manganese in tidal estuarine system in Taiwan. Environmental Science and Pollution Research. 2019; 27 (1):510-531.

Chicago/Turabian Style

Wen-Cheng Liu; Poi-Jiu Ken; Hong-Ming Liu. 2019. "Transport and distribution of manganese in tidal estuarine system in Taiwan." Environmental Science and Pollution Research 27, no. 1: 510-531.

Original article
Published: 26 April 2019 in Environmental Fluid Mechanics
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A three-dimensional hydrodynamic, suspended sediment, and fecal coliform transport model was developed and applied to characterize the fecal coliform plume in the Danshuei River estuarine system and its adjacent coastal sea. The numerical model was calibrated and validated with time-series water levels and spatial distributions of suspended sediment and fecal coliform concentrations in 2012 and 2013, respectively. Three indices (i.e., mean absolute error, root-mean-square error, and skill score) were used to compare the predicted results and measured data for assessing the performance of the model. Quantitatively, there was good agreement between the simulation and the measurement results. The validated model was later applied to explore the influence of river discharge and wind stress on the fecal coliform plume in the Danshuei River coastal area. In the absence of wind stress, no cyclonic circulation occurs as a result of river discharge under flood conditions. However, anticyclone circulation occurs on the east coast of the Danshuei River mouth at low river discharge. The plume distances of fecal coliform from the Danshuei River mouth reach 17 km and 5 km under flood flow and Q50 flow conditions, respectively. In the absence of river discharge, the plume distance of fecal coliform is confined to the Danshuei River mouth. Consequently, the wind directions control the upwelling and downwelling plumes. If the river discharge and wind stress are included in the model simulations, the surface fecal coliform concentrations are flushed out of the Danshuei River mouth and move to the southwestern coast as a result of the wind’s favoring downwelling. Conversely, the fecal coliform concentrations are flushed out of the Danshuei River mouth and flow to the northeastern coast, with the wind favoring upwelling. Comparing simulated results with and without wind stresses, the plume distance/area of fecal coliform decreases with the inclusion of wind stress.

ACS Style

Wen-Cheng Liu; Hong-Ming Liu. Investigation of the fecal coliform plumes induced by river discharge and wind stress using a three-dimensional model. Environmental Fluid Mechanics 2019, 20, 19 -49.

AMA Style

Wen-Cheng Liu, Hong-Ming Liu. Investigation of the fecal coliform plumes induced by river discharge and wind stress using a three-dimensional model. Environmental Fluid Mechanics. 2019; 20 (1):19-49.

Chicago/Turabian Style

Wen-Cheng Liu; Hong-Ming Liu. 2019. "Investigation of the fecal coliform plumes induced by river discharge and wind stress using a three-dimensional model." Environmental Fluid Mechanics 20, no. 1: 19-49.

Article
Published: 19 January 2019 in Journal of Earth System Science
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A three-dimensional, unstructured-grid hydrodynamic and suspended-sediment transport model was developed to simulate the temporal and spatial variations of suspended sediment and was applied to the subtropical subalpine Tsuei-Feng Lake (TFL) of Taiwan. The model was validated with measured water level and suspended-sediment concentration in 2009, 2010 and 2011. The overall model simulation results are in quantitative agreement with the observational data. The validated model was then applied to explore the most important parameter that affects the suspended-sediment concentration and to investigate the effect of wind stress on the mean current and suspended-sediment distribution in this shallow lake. Modelling results of the sensitivity analysis revealed that the settling velocity is a crucial parameter and the erosion rate is less important in the suspended-sediment transport model. Remarkable lake circulation was found based on the strength of wind speed and wind direction. A strong wind would result in a higher mean current in the top layer and suspended-sediment distribution in the top and bottom layers. This study demonstrated that wind stress played a significant influence on mean circulation and suspended-sediment transport in a shallow lake.

ACS Style

Wen-Cheng Liu; Hong-Ming Liu; Chih-Yu Chiu. Investigating suspended-sediment transport in a shallow lake using a three-dimensional hydrodynamic and sediment model. Journal of Earth System Science 2019, 128, 1 -19.

AMA Style

Wen-Cheng Liu, Hong-Ming Liu, Chih-Yu Chiu. Investigating suspended-sediment transport in a shallow lake using a three-dimensional hydrodynamic and sediment model. Journal of Earth System Science. 2019; 128 (2):1-19.

Chicago/Turabian Style

Wen-Cheng Liu; Hong-Ming Liu; Chih-Yu Chiu. 2019. "Investigating suspended-sediment transport in a shallow lake using a three-dimensional hydrodynamic and sediment model." Journal of Earth System Science 128, no. 2: 1-19.

Journal article
Published: 22 December 2018 in Continental Shelf Research
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Global sea level rise (SLR) rates are accelerating, and abnormal weather is occurring more frequently due to global warming and climate change. SLR could intensify coastal disasters and concerns of an increase in storminess. In this study, a two-dimensional advanced circulation model (ADCIRC) was used to simulate tides and storm surges around the Taiwan coast. The model was calibrated and verified using observed tides and storm surges at four tidal gauge stations, including Taipei Tamsui, Taichung Harbor, Kaohsiung Harbor, and Hualien Harbor, based on historical typhoon events. The root mean square error and skill value of the differences between the computed and observed water levels for model calibration and validation were in the range of 0.08~0.27 m and 0.92~0.99, respectively. The results showed a reasonable agreement between the simulated and observed tidal levels and surge heights. The validated model was then used to assess the impact of SLR on the tides and surge heights. Four typical typhoon events under present-day sea level conditions and under SLR conditions of 0.87 m and 1.9 m were used for the model simulations. The simulated results show that the largest differences in water levels and surge heights between present-day conditions and SLR of 0.87 m and 1.9 m are found at Taichung Harbor compared to other three-gauge stations. The changes in M2 tidal amplitude are less than 1 cm due to sea level rise. Moreover, the timing of the M2 tide was earlier by approximately 4.7 min and 9 min under SLR 0.87 m and 1.9 m, respectively, at Taichung Harbor. The maximum increases in water level ranged from 9.2 cm to 13.7 cm under SLR of 0.87 m and from 19.2 cm to 24.8 cm under SLR of 1.9 m at Taichung Harbor. The peak water level can significantly increase as a result of the SLR. All of these characteristics respond to an SLR with nonlinear and nonuniform behavior.

ACS Style

Wen-Cheng Liu; Wei-Che Huang. Influences of sea level rise on tides and storm surges around the Taiwan coast. Continental Shelf Research 2018, 173, 56 -72.

AMA Style

Wen-Cheng Liu, Wei-Che Huang. Influences of sea level rise on tides and storm surges around the Taiwan coast. Continental Shelf Research. 2018; 173 ():56-72.

Chicago/Turabian Style

Wen-Cheng Liu; Wei-Che Huang. 2018. "Influences of sea level rise on tides and storm surges around the Taiwan coast." Continental Shelf Research 173, no. : 56-72.

Journal article
Published: 25 May 2018 in Forests
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The productivity of forests is often considered to be limited by the availability of phosphorus (P). Knowledge of the role of organic and inorganic P in humid subtropical forest soils is lacking. In this study, we used chemical fractionation and 31P nuclear magnetic resonance (NMR) spectroscopy to characterize the form of P and its distribution in undisturbed perhumid Taiwan false cypress (Chamaecyparis formosensis Matsum.) forest soils. The toposequence of transects was investigated for the humic layer from summit to footslope and lakeshore. The clay layer combined with a placic-like horizon in the subsoil may affect the distribution of soil P because both total P and organic P (Po) contents in all studied soils decreased with soil depth. In addition, Po content was negatively correlated with soil crystalline Fe oxide content, whereas inorganic P (Pi) content was positively correlated with soil crystalline Fe oxide content and slightly increased with soil depth. Thus, Pi may be mostly adsorbed by soil crystalline Fe oxides in the soils. Among all extractable P fractions, the NaOH-Po fraction appeared to be the major component, followed by NaHCO3-Po; the resin-P and HCl-Pi fractions were lowest. In addition, we found no typical trend for Pi and Po contents in soils with topographical change among the three sites. From the 31P-NMR spectra, the dominant Po form in soils from all study sites was monoesters with similar spectra. The 31P-NMR findings were basically consistent with those from chemical extraction. Soil formation processes may be the critical factor affecting the distribution of soil P. High precipitation and year-round high humidity may be important in the differentiation of the P species in this landscape.

ACS Style

Yo-Jin Shiau; Chung-Wen Pai; Jeng-Wei Tsai; Wen-Cheng Liu; Rita S. W. Yam; Shih-Chieh Chang; Sen-Lin Tang; Chih-Yu Chiu. Characterization of Phosphorus in a Toposequence of Subtropical Perhumid Forest Soils Facing a Subalpine Lake. Forests 2018, 9, 294 .

AMA Style

Yo-Jin Shiau, Chung-Wen Pai, Jeng-Wei Tsai, Wen-Cheng Liu, Rita S. W. Yam, Shih-Chieh Chang, Sen-Lin Tang, Chih-Yu Chiu. Characterization of Phosphorus in a Toposequence of Subtropical Perhumid Forest Soils Facing a Subalpine Lake. Forests. 2018; 9 (6):294.

Chicago/Turabian Style

Yo-Jin Shiau; Chung-Wen Pai; Jeng-Wei Tsai; Wen-Cheng Liu; Rita S. W. Yam; Shih-Chieh Chang; Sen-Lin Tang; Chih-Yu Chiu. 2018. "Characterization of Phosphorus in a Toposequence of Subtropical Perhumid Forest Soils Facing a Subalpine Lake." Forests 9, no. 6: 294.

Preprint
Published: 02 May 2018
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The productivity of forests is often considered to be limited by the availability of phosphorus (P). Knowledge of the role of organic and inorganic P in humid subtropical forest soils is lacking. In this study, we used chemical fractionation and 31P nuclear magnetic resonance (NMR) spectroscopy to characterize the form of P and its distribution in undisturbed perhumid Chamaecyparis forest soils. The toposequence of transects was investigated for the humic layer from summit to footslope and lakeshore. The clay layer combined with a placic-like horizon in the subsoil may affect the distribution of soil P because both total P and organic P (Po) contents in all studied soils decreased with soil depth. In addition, Po content was negatively correlated with soil crystalline Fe oxide content, whereas inorganic P (Pi) content was positively correlated with soil crystalline Fe oxide content and slightly increased with soil depth. Thus, Pi may be mostly adsorbed by soil crystalline Fe oxides in the soils. Among all extractable P fractions, the NaOH-Po fraction appeared to be the major component, followed by NaHCO3-Po; the resin-P and HCl-Pi fractions were lowest. In addition, we found no typical trend for Pi and Po contents in soils with topographical change among the three sites. From the 31P-NMR spectra, the dominant Po form in soils from all study sites was monoesters with similar spectra. The 31P-NMR findings were basically consistent with those from chemical extraction. Soil formation processes may be the critical factor affecting the distribution of soil P. High precipitation and year-round high humidity may be important in the differentiation of the P species in this landscape.

ACS Style

Yo-Jin Shiau; Chung-Wen Pai; Jeng-Wei Tsai; Wen-Cheng Liu; Rita S.W. Yam; Shih-Chieh Chang; Sen-Lin Tang; Chih-Yu Chiu. Characterization of Phosphorus in a Toposequence of Subtropical Perhumid Forest Soils Facing a Subalpine Lake. 2018, 1 .

AMA Style

Yo-Jin Shiau, Chung-Wen Pai, Jeng-Wei Tsai, Wen-Cheng Liu, Rita S.W. Yam, Shih-Chieh Chang, Sen-Lin Tang, Chih-Yu Chiu. Characterization of Phosphorus in a Toposequence of Subtropical Perhumid Forest Soils Facing a Subalpine Lake. . 2018; ():1.

Chicago/Turabian Style

Yo-Jin Shiau; Chung-Wen Pai; Jeng-Wei Tsai; Wen-Cheng Liu; Rita S.W. Yam; Shih-Chieh Chang; Sen-Lin Tang; Chih-Yu Chiu. 2018. "Characterization of Phosphorus in a Toposequence of Subtropical Perhumid Forest Soils Facing a Subalpine Lake." , no. : 1.

Journal article
Published: 07 March 2018 in Water
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An automated discharge imaging system (ADIS), which is a non-intrusive and safe approach, was developed for measuring river flows during flash flood events. ADIS consists of dual cameras to capture complete surface images in the near and far fields. Surface velocities are accurately measured using the Large Scale Particle Image Velocimetry (LSPIV) technique. The stream discharges are then obtained from the depth-averaged velocity (based upon an empirical velocity-index relationship) and cross-section area. The ADIS was deployed at the Yu-Feng gauging station in Shimen Reservoir upper catchment, northern Taiwan. For a rigorous validation, surface velocity measurements were conducted using ADIS/LSPIV and other instruments. In terms of the averaged surface velocity, all of the measured results were in good agreement with small differences, i.e., 0.004 to 0.39 m/s and 0.023 to 0.345 m/s when compared to those from acoustic Doppler current profiler (ADCP) and surface velocity radar (SVR), respectively. The ADIS/LSPIV was further applied to measure surface velocities and discharges during typhoon events (i.e., Chan-Hom, Soudelor, Goni, and Dujuan) in 2015. The measured water level and surface velocity both showed rapid increases due to flash floods. The estimated discharges from ADIS/LSPIV and ADCP were compared, presenting good consistency with correlation coefficient R = 0.996 and normalized root mean square error NRMSE = 7.96%. The results of sensitivity analysis indicate that the components till (τ) and roll (θ) of the camera are most sensitive parameters to affect the surface velocity using ADIS/LSPIV. Overall, the ADIS based upon LSPIV technique effectively measures surface velocities for reliable estimations of river discharges during typhoon events.

ACS Style

Wei-Che Huang; Chih-Chieh Young; Wen-Cheng Liu. Application of an Automated Discharge Imaging System and LSPIV during Typhoon Events in Taiwan. Water 2018, 10, 280 .

AMA Style

Wei-Che Huang, Chih-Chieh Young, Wen-Cheng Liu. Application of an Automated Discharge Imaging System and LSPIV during Typhoon Events in Taiwan. Water. 2018; 10 (3):280.

Chicago/Turabian Style

Wei-Che Huang; Chih-Chieh Young; Wen-Cheng Liu. 2018. "Application of an Automated Discharge Imaging System and LSPIV during Typhoon Events in Taiwan." Water 10, no. 3: 280.

Preprint
Published: 29 May 2017
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A three-dimensional, unstructured grid, hydrodynamic and suspended-sediment transport model (i.e., SELFE-SED) was developed to simulate temporal and spatial variations of suspended sediment and was applied to the subtropical subalpine Tsuei-Feng Lake (TFL) of Taiwan. The model was validated with measured water level and suspended‑sediment concentration in 2009, 2010, and 2011. The overall model simulation results are in quantitative agreement with the observational data. The validated model was then applied to explore the most important parameter that affects the suspended-sediment concentration and to investigate the effect of wind stress on the mean current and suspended‑sediment distribution in this shallow lake. Modeling results of sensitivity analysis reveal that the settling velocity is a crucial parameter and erosion rate is less important in the suspended-sediment transport model. Remarkable lake circulation was found based on the strength of wind speed and wind direction. Strong wind would result in higher mean current in the top layer and suspended-sediment distribution in the top and bottom layers. This study demonstrated that the wind stress played a significant influence on mean circulation and suspended-sediment transport in a shallow lake.

ACS Style

Hong-Ming Liu; Wen-Cheng Liu; Chih-Yu Chiu. Investigating Suspended-Sediment Transport in a Shallow Lake Using a Three-Dimensional Model. 2017, 1 .

AMA Style

Hong-Ming Liu, Wen-Cheng Liu, Chih-Yu Chiu. Investigating Suspended-Sediment Transport in a Shallow Lake Using a Three-Dimensional Model. . 2017; ():1.

Chicago/Turabian Style

Hong-Ming Liu; Wen-Cheng Liu; Chih-Yu Chiu. 2017. "Investigating Suspended-Sediment Transport in a Shallow Lake Using a Three-Dimensional Model." , no. : 1.

Journal article
Published: 10 March 2017 in Water
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A large amount of accurate river cross-section data is indispensable for predicting river stages. However, the measured river cross-section data are usually sparse in the transverse direction at each cross-section as well as in the longitudinal direction along the river channel. This study presents three algorithms to resample the river cross-section data points in both the transverse and longitudinal directions from the original data. A two-dimensional (2D) high-resolution unstructured-grid hydrodynamic model was used to assess the performance of the original and resampled cross-section data on a simulated river stage under low flow and high flow conditions. The simulated river stages are significantly improved using the resampled cross-section data based on the linear interpolation in the tidal river and non-tidal river segments. The resampled cross-section data based on the linear interpolation satisfactorily maintains the topographic and morphological features of the river channel, especially in the meandering river segment. Furthermore, the performance of the 2D and three-dimensional (3D) models on the simulated river stage was also evaluated using the resampled cross-section data. The results indicate that the 2D and 3D models reproduce similar river stages in both tidal and non-tidal river segments under the low flow condition. However, the 2D model overestimates the river stages in both the tidal and non-tidal river segments compared to the 3D model under the high flow condition. The model sensitivity was implemented to investigate the influence of bottom drag coefficient and vertical eddy viscosity on river stage using 2D and 3D models based on the linear interpolation method to resample river bed cross-section. The results reveal that the change of bottom drag coefficient has a minor impact on river stage, but the change of vertical eddy viscosity is insensitive to river stage.

ACS Style

Wei-Bo Chen; Wen-Cheng Liu. Modeling the Influence of River Cross-Section Data on a River Stage Using a Two-Dimensional/Three-Dimensional Hydrodynamic Model. Water 2017, 9, 203 .

AMA Style

Wei-Bo Chen, Wen-Cheng Liu. Modeling the Influence of River Cross-Section Data on a River Stage Using a Two-Dimensional/Three-Dimensional Hydrodynamic Model. Water. 2017; 9 (3):203.

Chicago/Turabian Style

Wei-Bo Chen; Wen-Cheng Liu. 2017. "Modeling the Influence of River Cross-Section Data on a River Stage Using a Two-Dimensional/Three-Dimensional Hydrodynamic Model." Water 9, no. 3: 203.