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Chen C.-F.,Chinese Culture University | Liu C.-M.,The Chinese Association of Low Carbon Environment
Natural Hazards | Year: 2014

The combination of climate change and urbanization is worsening urban flooding problems. Estimating the amount of rainfall that a city can tolerate without flooding is a fundamental task that is difficult to perform, although large amounts of resources are invested in urban flood control. The purpose of this study is to determine the tolerance threshold for stormwater in a city. Based on hydrometeorological characteristics and existing flood control facilities, the urban adaptive water capacity is analyzed to determine the critical rainfall loading. Different critical levels are defined. The low critical point represents the beginning of the water accumulation, while the intermediate and high critical points are defined as flooding with heights of 300 and 600 cm, respectively, in low-lying areas. This study adopts a simple conceptual method to illustrate the critical levels instead of applying complex hydrologic and hydraulic modeling, which require high-resolution spatial data. Three cities and one township in Taiwan are used as urban case studies and to verify the conceptual method. As the capital, Taipei City utilizes the highest flood control engineering technology of our case studies; it is also the site in which the lowest rainfall thresholds cause the accumulation of water to reach the intermediate and high critical points because its small 'internal water areas' increase the height of floods rapidly. Conversely, Taichung City has a large internal water area that can disperse accumulating waters without increasing flood height. The estimations of urban storm tolerance thresholds increase the understanding of the limitations of water protection facilities. These estimations may be combined with rainfall forecasts to increase early warning functions and provide a reference point for subsequent planning related to urban flood adaptation strategies. © 2013 Springer Science+Business Media Dordrecht. Source

Lin S.-H.,National Taiwan University | Lin S.-H.,Research Center for Typhoon and Society | Liu C.-M.,The Chinese Association of Low Carbon Environment
International Journal of Climatology | Year: 2013

Data assimilation is important for the spatial analysis of small regions with complex terrain and diverse climates and for interpolation among observations. A data assimilation method incorporating observations, coarse-grid re-analysis data and physiographical features is demonstrated to generate high-resolution temperature data for small islands such as Taiwan. The method is also able to weigh physiographic and anthropogenic factors. Among the spatial factors, the orographic effect is the dominating factor and the lapse rate varies seasonally. Population density is significantly related to temperature, which may correspond to the urban heat-island (UHI) effect. It is also shown that an anthropogenic factor could be used with this interpolation method to explain the details of the temperature variation. The data assimilation model provides an opportunity to assess the extent to which simple statistical regression equations, calibrated from natural variability, can reproduce climate changes driven by land effects without considering a complex climate model. Copyright © 2012 Royal Meteorological Society. Source

Liu C.-M.,The Chinese Association of Low Carbon Environment | Chen J.-W.,Dingtai Co. | Tsai J.-H.,National Taipei University of Technology | Lin W.-S.,The Chinese Association of Low Carbon Environment | And 2 more authors.
Journal of the Air and Waste Management Association | Year: 2012

This study determines whether environment-protecting pervious pavement can dilute pollutants immediately after emissions from vehicle. The turbulence-driven dry-deposition process is too slow to be considered in this aspect. The pavement used is the JW pavement (according to its inventor's name), a high-load-bearing water-permeable pavement with patents in over 100 countries, which has already been used for more than 8 years in Taiwan and is well suited to replacing conventional road pavement, making the potential implementation of the study results feasible. The design of this study included two sets of experiments. Variation of the air pollutant concentrations within a fenced area over the JW pavement with one vehicle discharging emissions into was monitored and compared with results over a non-JW pavement. The ambient wind speed was low during the first experiment, and the results obtained were highly credible. It was found that the JW pavement diluted vehicle pollutant emissions near the ground surface by 40%-87% within 5 min of emission; whereas the data at 2 m height suggested that about 58%~97% of pollutants were trapped underneath the pavement 20 min after emission. Those quantitative estimations may be off by ±10%, if errors in emissions and measurements were considered. SO2 and CO2 underwent the most significant reduction. Very likely, pollutants were forced to move underneath due to the special design of the pavement. During the second experiment, ambient wind speeds were high and the results obtained had less credibility, but they did not disprove the pollutant dilution capacity of the JW pavement. In order to track the fate of pollutants, parts of the pavement were removed to reveal a micro version of wetland underneath, which could possibly hold the responsibility of absorbing and decomposing pollutants to forms harmless to the environment and human health. Implications: The potentials of pervious pavements in improving the urban environment are advancing every day. In this paper, the authors present evidences of automobile exhaust dilution by a special-designed high-load-bearing pervious pavement. This study outlines an effective approach on evaluating such dilution effect; still more studies are needed. Supplemental Materials: Supplemental Materials: Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for experimental studies of the dilution of vehicle exhaust pollutants by environment-protecting pervious pavement. © 2012 Copyright 2012 A&WMA. Source

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