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遙測影像與數值地形模型於堰塞湖災害評估之應用

Application of Satellite Images and DEM for the Hazard Assessment of Landslide Dams

摘要


堰塞湖一旦形成後,衍生災害可概分兩類:第一類爲上游迴水淹沒、第二類爲潰壩造成下游夾砂水流或洪水災害。遙測技術對於這兩類災害快速評估工作之推動可扮演相當關鍵的角色。本研究整合衛星影像以及數值地形模型,配合可快速進行空間計算之GIS系統,提出一套堰塞湖形成初期之快速分析與評估程序。流程包括:(1)及時取得足夠清晰之衛星影像,判釋堰塞湖位置;(2)配合數值地形模型獲得天然壩之幾何資訊(壩頂高程、壩長、壩寬、壩高)以及上游集水面積;(3)根據數值地形資料繪製水位高程-湖水體積圖,並利用多期衛星影像搭配數值地形模型進行堰塞湖水位高程監測;(4)估計淨入流流量、溢流時間以及上游淹沒範圍與時間之關係;(5)利用地形指標或統計模型以評估天然壩之穩定性。本文以汶川地震於北川形成之唐家山堰塞湖爲例,說明如何利用福衛二號影像以及SRTM數值地形資料於第一時間提供堰塞湖防、救災工作推動所需之重要資訊。本研究重要結論包括:(1)地震或極端降雨後,應於可能的最短時間內,取得影像解析度至少能描繪天然壩堆積邊界之清晰衛星影像;(2)評估所需之DEM精度以5公尺爲佳;(3)堰塞湖水位高程研判應以堰塞湖水陸交界找尋多點進行高程平均,以提高湖水位高程研判之準確度;(4)堰塞湖後期流量推估對水位高程估計較敏感,因此欲根據遙測影像及DEM進行水位高程監測以及淹沒範圍預測,應注意DEM水平位置及高程誤差可能造成之影響。

並列摘要


After the formation of a landslide dam, the related impacts can be divided into upstream (rising backwater) and down stream (dam breaching with outburst flood and debris flow) components. Since both components may occur soon after the landslide dams the river, rapid assessment of the related hazards is crucial. Remote sensing technology could play a key role for decision-making to prevent or minimize the disaster due to a landslide dam. This research proposed a procedure utilizing the satellite images, DEM, and GIS system to quickly assess the potential hazards associated with the formation of landslide dams. To begin with, the location of the landslide dam should be identified from the satellite images. Secondly, the elevation of the landslide-dam top, dam geometry, and catchment area should be determined based on the satellite images and DEM. It follows a production of the water level-lake storage curve of the natural lake. Different periods of the satellite image could be used for monitoring the buildup of the backwater. Consequently, the inflow could be estimated using the water level-lake storage curve and the monitored water level. Based on the estimated inflow, the time for overtopping and the flooding area of the backwater could be determined. Meanwhile, the stability of landslide dam could be evaluated using the geo-morphological and hydro-geological characteristics estimated from the satellite images and DEM. A large landslide dam formed after the 2008 Wenchuan Earthquake is adopted as an example for demonstrating the hazard assessment procedure. The case history successfully illustrated how the high-resolution FORMOSAT-2 satellite images and the DEM derived from Shuttle Radar Topographic Mission (SRTM) could be efficiently served as the powerful tools to provide important information for decision making on the action of hazard mitigation soon after the formation of a landslide dam.

被引用紀錄


簡翊文(2014)。暴雨誘發邊坡崩滑運動模擬與模擬方法改良〔碩士論文,國立交通大學〕。華藝線上圖書館。https://doi.org/10.6842%2fNCTU.2014.00774

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