Browsing by Author "Hsu, Yung-Chia"

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An Investigation of DEM Resolution Influence on Flood Inundation Simulation
(2016-01-01)
Hsu, Yung-Chia
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Prinsen, Geert
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Bouaziz, Laurene
;
Lin, Yi-Jun
;
Dahm, Ruben
This study investigates the influence of DEM resolutions on flood inundation simulation. Sanyei drainage area of Tainan City is taken as a case study. The catchment of Sanyei area is 43.7 km2 with a main stream of 6.7 km and elevations running from 2 m to 30 m. This study uses 1x1 m LiDAR DEM of Sanyei area as a basis. To do pure 2D flood simulation, the channel elevation is adjusted based on the cross-sectional measurements. The channel adjusted 1x1m DEM is later used as basis to aggregate several DEMs including: 5x5m, 10x10m, 20x20m, 40x40m. Five flood inundation models were built based on the 5 DEMs mentioned above with a same model setting. Results show that the inundation area evaluation increases with coarser DEMs. Specifically, the inundation area given by the 40x40m DEM is 1.5 times greater than that given by the 1x1m DEM. This may not only lead to different decision making in evacuation route and responses, but also the evaluation of economic loss and project planning, etc. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.
Dam overtopping risk assessment considering inspection program
(2008-04-01)
Kuo, Jan-Tai
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Hsu, Yung-Chia
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Tung, Yeou-Koung
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Yeh, Keh-Chia
;
Wu, Jian-De
Safety inspection of large dams in Taiwan is conducted every 5 years. The practice does not take into consideration uncertainty of dam conditions. The goal of this study is to determine the optimal dam inspection interval under the consideration of overtopping risk incorporating uncertainty gate availability. In earlier studies, assessment of overtopping risk only considered the uncertainties in reservoir properties and natural randomness of hydrologic events without giving much thought to the availability of spillway gates. As a result, the overtopping risk could be underestimated. In this study, an innovative concept is proposed to evaluate dam overtopping by taking into account spillway gate availability. The framework consists of three parts: (1) evaluation of conditional overtopping risk for different numbers of malfunctioning spillway gates; (2) evaluation of spillway gate availability; and (3) dam inspection scheduling. Furthermore, considerations are given to overtopping risk, inspection cost, and dam break cost for determining the optimal inspection schedule. The methodology is applied to the Shihmen Reservoir in Taiwan and to evaluate its time-dependent overtopping risk. Results show that overtopping risk considering the availability of the spillway gates is higher than the one without considering the availability of the spillway gates.
Evaluation of dam overtopping probability induced by flood and wind
(2011-01-01)
Hsu, Yung-Chia
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Tung, Yeou-Koung
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Kuo, Jan-Tai
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防災與水環境研究中心
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Disaster Prevention and Water Environment Research Center
This study develops a probability-based methodology to evaluate dam overtopping probability that accounts for the uncertainties arising from wind speed and peak flood. A wind speed frequency model and flood frequency analysis, including various distribution types and uncertainties in their parameters, are presented. Furthermore, dam overtopping probabilities based on monthly maximum (MMax) series models are compared with those of the annual maximum (AMax) series models. An efficient sampling scheme, which is a combination of importance sampling (IS) and Latin Hypercube sampling (LHS) methods, is proposed to generate samples of peak flow rate and wind speed especially for rare events. Reservoir routing, which incorporates operation rules, wind setup, and run-up, is used to evaluate dam overtopping probability.
Uncertainties in the Methods of Flood Discharge Measurement
(2013-01-01)
Chen, Yen-Chang
;
Hsu, Yung-Chia
;
Kuo, Kuang-Ting
;
防災與水環境研究中心
;
Disaster Prevention and Water Environment Research Center
This study demonstrates an application of uncertainty analysis in evaluating methods of discharge measurement including: the velocity-area, rating curve and efficient methods based on the probabilistic velocity distribution equation. The measurement of river discharge plays a large part in the distribution of water resources. The conventional methods of discharge measurement are costly, time-consuming, and dangerous. Therefore the efficient method of discharge measurement which bases on the relationship between maximum and mean velocities being constant was employed to justify its alternative for the conventional methods: velocity-area and rating curve methods. Distribution test was applied to investigate the statistical properties of the uncertainties involved in the three methods of discharge measurement. Latin hypercube sampling (LHS) method was employed accordingly to assess the discharge features of the three methods of discharge measurement. The main purpose of this study is to quantify the uncertainty involved in several discharge measurement methods and justify the availability and reliability of using the efficient method as an alternative of the conventional methods. Results show that the correlation analysis also validates that the efficient method is a more reliable method than the rating curve method to yield accurate discharge measurements. Moreover, it also yielded comparably accurate measurements as those by the velocity-area method.