圖書典藏及影音數位平台

本計畫主要係探討海岸地區溢淹災害致災因子(如颱風暴潮、波浪及洪水量等)，應用不確定性概念，分析各種組合，以瞭解災害可能的影響程度，作為後續相關防護策略研擬依據。

Taiwan is an island country surrounded by the sea.Generally, in average, thereare four typhoons attacking Taiwan area in summer and autumn seasons every year. During a typhoon event, the total water levelaffected by combined effects of storm surge, wave, astronomical tide and fluvial flood would become much higher. Once the increased water level crossesan embankment,the resulting coastal inundation would lead to severedamages of properties and losses of lives. For instance, Typhoon Fanapi (in 2010) caused 2 deaths and 111 injured.Estimated economic losses wasover 3.4 billion. During the past decade, most case studies over the world adopting probabilistic simulationsrather than conventional deterministic analysis have taken uncertaintyand risk into account to achieve effective management and prevention of coastal disasters. These projects proposedquite similarmethodologyalthough they may handle a wide range of problems (e.g.,surge, tsunami, flooding, and coastal erosion) using various modeling tools with different focused scales (e.g., low-resolution preliminary studies, detailed site-specific assessments, oreven coastal structure designs against possible failure mechanisms). Basic idea is to consider physical factors in a possible rangeand evaluate their influences on the induced disaster (i.e., uncertainty). As a result, more information (i.e., probability) of risk levels can be provided for further judgment and decision-making. Themain objective of this project is to establish the concept and overall research frameworkof risk and uncertainty for our coastal protectionplanning authorities. The coastal water level during typhoon events will be investigated in this two-year study, where surges and waves will be examinedin the first and second year, respectively. Besides, some coastal inundation tests in a selected study area will be conducted using different downstream conditions (e.g., a design value of 500-yearreturn period in 5 %, 50%, and 95% confidence levels). Modeled results (i.e., inundation depths and extents) will be compared to reveal the influences of uncertainty in coastal planning. Through the review of work scheme execution, expertsin the meeting suggested an appropriate way under limitedbudget, tight schedule, and computation demands. Taiwan’s coastal areacan be divided into six regionsfor carrying out uncertainty analysis of the water level.The southwesterncoastal area(i.e., Yunlin, Chiayi, and Tainan)inthe first-class protection zonewas recommended for the case study ,i.e., Tsengwen river estuary and its adjacent coastal seas. In this year, various case studiesand most advanced approaches used in America, England, Netherland, Japan, and New Zealand werereviewed. Marine, meteorology, and hydrologic observation data werecollected(from the central weather bureau and water resources agency). The Princeton Ocean Model (POM)was applied to simulate storm surges with careful validation against historical typhoon events. Further, five typhoon physical parameters (i.e., central pressure, maximum wind speed, radiusof maximum wind, foreword speed, and translation angle) were systematically analyzedto estimate the probability density functions (PDFs). Based uponthese relationships, some representative values of typhoon parameters were combined. The corresponding storm surges(as a lookup table or database) were obtained using POM simulations. Last, the Monte Carlo simulationsfor estimating risk and uncertainty of storm surges werecarried out using a three-step procedure. Various possible synthetic typhoons in a 500-year time period were generated based on the PDFs.The surge deviationswere estimated from the lookup table using interpolation. With 100 realizations of 500-year life cycle, therisk and uncertainty of storm surges(i.e., different return periods and confidence levels) were obtainedfollowing the conventional statistical analysis (i.e., extreme value distribution).Overall, more complete information on storm surges was obtained and can be providedas a reference for disaster prevention, mitigation and a variety of related decision-making.