| dc.description.abstract | The Taipei City is crowded with a large population today. Most areas in the City were developed for commercial or residential use. Very few considerations have been given to reserving massive spaces for leisure activities. In order to enhance the living quality for citizens, the Taipei City Government plans to utilize the upper platforms of outer riverside levees as open public facilities such as parks, sports fields, or parking lots. These planning activities are often carried out at the initial design phase of maintenance projects for rivers that are classified as City-governed.
Evacuating gates on the levees are established at proper spots. Through those evacuating gates, people and vehicles can be evacuated before the rivers overflow the platforms during the typhoon or flood seasons. At normal times, the same evacuating gates are used as entrances for engineering trucks when maintenance of those public facilities are carried out.
When a typhoon attacks, evacuating gates must be closed in time to secure the lives and properties inside the levees. At present, the Taipei City Government relies on information provided by the Central Weather Bureau (CWB) to determine the right timing for closing evacuating gates. The Taipei City Government will inform Taipei City Government Disaster Response Center to issue press releases and close every evacuating gates in the City when the following criteria are met: a) CWB issues a terrestrial typhoon alert, b) either the water level of Tamshui River at Taipei Bridge exceeds 2.4 meters, or that of Keelung River at Tachih Bridge exceeds 3.1 meters. However, according to the data for typhoons and floods in past years, the warning water levels upon which decisions for closing evacuating gates were made are considered conservative, and could be properly adjusted.
This study analyzes the hydraulic data resulting from typhoons and floods in past years. It evaluates the appropriateness of current practice for closing evacuating gates, and suggests new water levels for closing those gates. Due to the uncertainties of hydrology and uncontrollable engineering factors when planning hydraulic engineering projects, it is quite likely that risks still exist after the projects are completed. This study also carries out recursive analysis with accumulated probability of both water levels and the number of typhoons and floods. It probes into the probability of risks associated with different water levels for closing gates, as well as the probability of risks associated with overflowed platforms. | en_US |