以風險為基礎的自然邊坡分級之探討-以臺北市為例

臺灣位處西太平洋颱風路徑區域及季風帶交會區，每年遭受多次颱風豪雨侵襲，加上地勢坡陡及地質脆弱，因此常發生坡地崩塌災情，造成生命財產的損失，為降低災害損失與有效管理坡地災害，當局需有合理且適用之邊坡安全評估及分級管理方法，所以自然邊坡風險等級之建立是一重要的課題。本研究於臺北市以風險為基礎進行自然邊坡風險管理研擬，在風險管理架構下針對國內外坡地災害風險管理之相關研究與理論以及針對邊坡風險評估、集群分析、易損性曲線、災害經濟損失風險感認等方法進行研析，研究目的有(1)建立本土化崩塌易損性函數；(2)崩塌災害經濟損失社會風險準則之建立；(3)自然邊坡風險等級研擬。本研究利用崩塌災害造成建築物與道路的毀損資料建立在地化易損性曲線，研究結果與義大利Umbria地區所調查分析的結果趨近於同一曲線，RC建築對於崩塌災害耐受力較鐵皮屋來的高，本研究建立了臺北市自然邊坡社會風險準則，這些準則可應用於臺北市已列管的自然邊坡之風險分析結果，並基於該準則建議邊坡分級處理對策。

關鍵字

風險分析與管理；易損性；風險感認；集群分析；風險準則

並列摘要

Taiwan is located in a zone jointly affected by typhoons originated in the western Pacific Ocean and monsoons. Several typhoons and heavy rainfall events are expected every year. Landslide events often occurred after heavy rains, given that slope lands are often steep and the geology is fragile in nature. Loss of life and assets are common unfortunate consequences of the disastrous events. It becomes required for the authorities to develop effective means for assessment of slope safety and slope land management. It is of great interest to establish a system to manage slope lands based on levels of risks. An initiative on risk-based management of natural slopes has been started in the Taipei City. Under the overall risk management framework, several relevant issues that need to be addressed were investigated in this study. Topics studied herein were grouped into three aspects, including (1) establishment of the vulnerability curve for landslide based on data in Taiwan, (2) establishment of societal risk criteria pertinent to the risk assessment approached employed for natural slopes in Taipei, and (3) development of a risk based managerial strategy for administration of natural slopes in Taipei. In this study, vulnerability curves both for building and roadway damages resulted from disastrous landslides in Taiwan were developed. It is found that the vulnerability curves based on Taiwan data are close to curves developed previously based on data in other locales. For a given landslide area, the vulnerability for the reinforced concrete structure is less than that for the metal sheet house, a common light weight housing seen in Taiwan. Risk criteria pertinent to the societal risk for natural slopes in Taipei also were established in this study. These criteria can be applied to the results of risk analysis for registered natural slopes in Taipei, and pertinent strategies for treatment and monitoring based on the levels of risk of these slopes also were developed. It is rational to administrate registered natural slopes based on categories of risks.