曾文水庫集水區崩塌特性之探討

Study on the Landslide Characteristics of Tseng-Wen Reservoir Watershed

胡原銘(Yang-Ming Hu)

指導教授 ： 曾志民

長榮大學/管理學院/土地管理與開發研究所/碩士(2006年)

https://doi.org/10.6833/CJCU.2006.00106

摘要

台灣山區陡峭的地形特徵，加上位處西北太平洋颱風路徑要衝，每年地震、颱風豪雨發生次數頻繁讓邊坡不穩定區域非常容易因暴雨影響發生土砂災害。水庫集水區大多位於地形險峻、地質條件不佳的山區，邊坡破壞情形相當頻繁。邊坡破壞或崩塌發生除造成表土流失外，上游集水區坍塌土石容易進入河道隨著水流匯入水庫而產生淤積，因而減少水庫蓄水量及降低原先之營運功能。邊坡因降雨產生之坍塌為水庫淤積主要泥砂來源，為了有效防止災害的再次發生，崩塌地的調查研究為重要事前準備工作，以便能充分掌握集水區崩塌發生特性，提供水庫集水區治理計畫參考依據。透過環境敏感區域的長期調查與分析工作，更可以了解崩塌發生潛因與災害特性。因此本研究先以SPOT影像判釋並分析颱風期間因降雨形成的新增崩塌地，並且觀察追蹤崩塌地於後續時間點變遷情形，其次則針對新增崩塌地之判釋結果與集水區之地質、地形、坡向及降雨特性進行關聯性分析，分析影響崩塌發生特性之因素。
從衛星影像資料所判釋之新增崩塌地結果發現，各颱風降雨事件不論是在空間分佈狀況或者崩塌數量和規模皆呈現明顯差異。敏督利颱風事件新增崩塌地主要發生在集水區中部，納莉和海棠颱風事件之新增崩塌地於空間分佈則較為平均。另外利用崩塌與集水區地文水文等環境屬性的關聯分析發現，崩塌較易發生之地形坡度集中於20°~40°之間，地質條件則以達邦層及南莊層等為主要發生崩塌地區，坡向方面以東南方坡向較容易發生坍塌破壞現象。受降雨衝擊程度影響，當地形坡度及地質分區符合上述條件時，接近颱風暴雨中心區域之崩塌潛勢將大為提高，顯示崩塌分佈特性主要還是與降雨有較高之關聯性，所以降雨對於崩塌發生地點、發生規模與數量上皆有相當程度之影響，即影響崩塌之發生降雨規模和強度大小是不可忽視的重要因素。

關鍵字

颱風降雨 ； 崩塌特性 ； 水庫集水區

並列摘要

The characteristics of the mountain in Taiwan are steepness; and it is located at the subtropical area of western Pacific and on the path of typhoons. As the result, the frequent earthquake, typhoon, and torrential rain cause the instable slope to have sand and soil disaster easily. The watershed of reservoir often located at mountain area where it has precipitous landforms and poor geology condition; the damage to slope happens frequently. The damage of slope or landslides will not only cause the soil to run off, the collapsed soil will also enters the reservoir with river and silt up. The amount of water a reservoir can store will decrease so the functionality will drop as well. The landslides caused by rainfall is the main source of soil that causes reservoir to silt up; in order to effectively prevent the disaster from happening again, the investigation of collapsed area is important preparation work to adequately grasp the characteristics of watershed collapse. It can provide a reference for reservoir management plan. Though the long-term investigation and analysis on the environmental sensitive area of environment, we can understand more about the characteristics of disaster and the cause. Therefore, this research first use SPOT satellite images to determine and analysis the new collapsed area during typhoon period due to rainfall, and trace the transition over time. Second, perform correlation between the determination result of new collapsed area and geology, direction of slope, and rainfall characteristics of reservoir to analysis the element that causes collapse to occur.
From the satellite image, we discovered that there is an obvious difference in the rainfall of Typhoon and space distribution, number of collapse, and seriousness of collapse. The collapses caused by Mindulle typhoon mainly take place at center of watershed. Nari and Haitang typhoon show a more average distribution of space and collapse area. Also, with the correlation of water environment analysis of collapse area and watershed, we discovered that the collapse often occurred where the steepness of the slope is between 20°~40°. For geology properties, Tapang formation and the Nanchuang formation is the main layer for collapse. The collapse often happened where the slope is facing southeast. Under the effect of rainfall, when the slope and geology properties meet the description above, the potential of collapse during the center of typhoon torrential rain will increase. It shows that the characteristics of collapse still have tighter relation with the rainfall. Therefore, rainfall has great affect on the collapse location, scale, and number. In other words, the scale and intensity of rainfall is an important element that affects the collapse.

並列關鍵字

typhpoon-rainfall ； landslide characteristics ； reservoir watershed

參考文獻

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