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  • 學位論文

曾文水庫集水區崩塌與降雨特性之研究

Characteristics of Landslides and Rainfall in the Tseng-Wen Reservoir Watershed

指導教授 : 李錦育

摘要


曾文水庫為供應嘉南平原解決水資源匱乏問題而興建,因颱風、豪雨等集中降雨事件導致水庫集水區上游大量崩塌,造成土砂淤積嚴重而減少庫容、縮短水庫壽命。而瞭解水庫集水區內發生崩塌的特性及潛在地區為首要工作,有助於提高集水區內土砂防治工程效益及延長水庫營運壽命。因此,本研究探討2001年~2010年間共計10場歷史颱風豪雨事件所誘發之崩塌地,分析崩塌地之時空演變趨勢,並利用GIS建置崩塌地屬性資料庫,分析各崩塌潛在因子(坡度、坡向、高程、地質、土壤、土地利用)與誘發因子(降雨)等共7個因子對崩塌之影響,並以不安定指數法探究崩塌潛勢分布之情形。   從崩塌地時空演變趨勢上,2009年莫拉克風災前,集水區崩塌率維持1%以下,莫拉克風災後造成大量新生崩塌,使崩塌率增至3.07%,隨後有逐年持續減少之趨勢。在崩塌地之規模與規模以上頻率分布上符合指數關係,小規模崩塌地發生之頻率較大規模崩塌地多,而誘發大規模崩塌之主要原因受到降雨特性影響。崩塌地空間分布集中於東北側之上游集水區,在坡度27°~43°、500m~1,250m的中海拔之範圍區間較易發生崩塌現象,而隨著坡度增加崩塌率也相對提高;此外,多數新生崩塌發生於舊有崩塌擴大及易向源侵蝕之區域範圍內。   分析崩塌與降雨特性之關聯性顯示:莫拉克颱風後由於坡地土體穩定性降低且既有崩塌較多,誘發崩塌之降雨條件宜隨之向下修正為適當。而在運用打荻氏公式預測集水區新增崩塌率方面,建議可採用集水區一日平均暴雨量取代平均累積雨量、臨界雨量採用130mm~250mm,較能符合本集水區及反應颱風降雨特性。   各崩塌影響因子權重依序為土地利用、土壤、坡度、降雨、地質、高程及坡向,前3者為人為可控制因子,能有效規劃則利於降低崩塌之可能;而以不安定指數法建置之集水區崩塌潛勢分布圖,經6場歷史颱風檢核高潛感區崩塌地之準確度達70.48%,可有效應用於集水區治理規劃及災害防治的初步預測。

並列摘要


Construction of Tseng-Wen reservoir is to solve the problem of lack of water resources in order to supply for the Chia-Nan plain region, because of the intense rainfall events such as typhoons and heavy rainfall, makes a large amount of landslides occurred in the upstream areas of the reservoir watersheds, causing the sediment siltation serious, reduce storage capacity and shorten the life of a reservoir. Therefore, It is an important work at understand characteristics of Landslides and landslide potential of Tseng-Wen reservoir watershed, help improve within sediment prevention benefits in the watershed and extend the operating life of the reservoir. Therefore, this study collect the landslides at 10 games of the typhoon and torrential rain between 2001~2010 to analysis the spatial and temporal variations of landslides. and using GIS technique to build the landslides database, Explore the Effects of the landslide of by potential factor (slope, aspect, elevation, geology, soils, land use) and triggering factors (rainfall). In addition, we also using the dangerous value method to discussed the landslide potential in the study.   Result shows that the spatial and temporal variations of landslides in the Tseng-Wen reservoir watershed. Before Typhoon Morakot, the landslide rate is remain below 1%, after Typhoon Morakot, makes a large amount of landslides occurred in the watershed, cause the landslide rate increased to 3.07%. Then, there are continue to decrease year by year trend. Result shows that the magnitude and frequency distribution of landslides, there are in line with the exponential relationship. By contrast, the frequency of small-scale landslides occurred more than the large-scale landslides, and lead to large-scale landslides occurred mainly by rainfall. The results show that the landslide caused in mainly take place in the upstream areas of the watersheds, it mostly happened at the height of 500~1,250meters, and the slope grade is at 27°~43°, and with increasing slope landslide rate is also enhanced. In addition, a large number of landslides also occurred in the enlarged area of former landslide zone and the headward erosion zone.   Result shows that the characteristics of landslides and rainfall. After Typhoon Morakot, the rainfall conditions induced collapse due to the Slope Stability reduce both collapse more, should be followed downward correction as appropriate. This research use Daogi formula to estimate the landslide rate in this watershed. It is advice may be given the average rainstorm of one day replace the average accumulated rainfall of watershed, and the critical rainfall may be given 130mm~250mm. This result is more in line with the characteristics of the watershed and the typhoons rainfall.   The dangerous value method to analyst the weights of landslide factors are land use, soil, slope, geology, rainfall, elevation and aspect respectively. The results show that the reasonable land use can reduce the possibility of landslide. A simple test result shows that the dangerous value method can predict landslide well. By using the multi-tempral landslide layers, the accuracy of the landslide potential maps can be compared, The analytical results show the predict landslide precisely where 70.48% landslide fall on the high susceptibility zone. Finally the analytical results can effective application to watershed management planning and preliminary forecast of disaster prevention.

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被引用紀錄


謝依霖(2015)。台東太麻里集水區崩塌因子之研究〔碩士論文,國立屏東科技大學〕。華藝線上圖書館。https://doi.org/10.6346%2fNPUST.2015.00007

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