| 摘要: | 淹水是台灣最常見的自然災害,在都市地區造成許多經濟損失和人身安全的傷亡, 更甚者,文獻指出都市的不透水鋪面透過改變水文循環的過程,會影響洪水的發生。本 研究之研究區台南市自 2001 年起淹水災情頻傳,伴隨著逐年成長的都市及不透水鋪面 面積,淹水在台南造成的損失將更加重大。為了評估台南市洪水發生之機率,本研究使 用邏輯迴歸分析不透水鋪面之面積及降雨參數(總雨量、延時和降雨強度)與歷史淹水事 件之關聯性,其中 80%之淹水記錄用於邏輯迴歸訓練,另外 20%則用於計算 AUC 以進 行邏輯迴歸之檢核驗證。為取得降雨參數及不透水鋪面面積所使用的資料包括 2001、 2004、2007、2010 和 2014 年共五年之中央氣象局降雨測站記錄及 Landsat 衛星影像, 其中不透水鋪面面積透過分析衛星影像,以 SVM 進行影像分類取得。從土地覆蓋圖之 分析結果發現,台南市之不透水鋪面面積於 2001 年至 2014 年約成長 108 平方公里,其 中 2001 年至 2007 年間有較顯著之成長,約成長 75 平方公里,為全部成長的 69%,高 成長之地區分別是安南、永康、仁德、歸仁、新市及新化等區,這些區域主要分佈在原 台南市之都市外圍,同時亦為過去發生淹水頻率較高之地區。邏輯迴歸之結果顯示,不 透水鋪面和降雨都和淹水發生有顯著的正向關聯,AUC (Area Under Curve)值則介於 0.83 至 0.88 間,顯示本研究所建立之邏輯迴歸模式,可用於評估台南市之淹水潛勢。綜合上 述研究成果,本研究之成果可為台南市提供都市成長及淹水災害防治等資訊,供政府或 都市規劃相關人員使用。;Flood, as known as the most frequent natural hazard in Taiwan, has induced severe damages of residents and properties in urban areas. Moreover, in urban areas, literatures indicated that impervious surface area (ISA) changes the hydrological procceses and therefore affects the occurrence of flood. The Tainan City, in the southwest part of Taiwan, have suffered from damages of flood for years, and is selected as the study area because of the high flood susceptibility with significant urban development in the past two decades. To estimate the likelihood of flood occurrence, which can be affected by ISA and rainfall, this study uses logistic regression to analyze the relationship between rainfall variables (total rainfall, rainfall duration and rainfall intensity), ISA and historical flood events. 80% of the historical flood events were used for the logistic regression training while the remaining 20% were utilized for model validation. Specifically, rainfall gauge records of 2001, 2004, 2007, 2010 and 2014 associated with 169 flood events were collected and mapped, and Landsat images were used to map land cover and ISA with SVM (support vector machine) classifier. The land cover maps show that the urban area increases around 108 km2 from 2001 to 2014, and the urban expansion is relatively significant during the period between 2001 and 2007, with area approximately 75km2. Saptially, the expansion areas are mostly appeared over Annan, Yongkang, Rende, Guiren, Xinshi and Xinhua districts, which mainly located at the fringe of original urban areas, as well as areas highly susceptible to flood. From the logistic regression analysis, the result shows that rainfall variables and ISA are effectively and significantly correlated to the flood occurrence. For model validation, the AUC (Area Under Curve) values range from 0.83 to 0.88 showing the well applicability of the model for flood susceptibility assessement. According to the findings, the study explores the relationship between urban development and flood in Tainan City, which can be usfur for flood hazard prevention and mitigation practices. |
