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| THE RELATIONSHIP BETWEEN LANDSLIDE AND GEOLOGY |
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| 林冠瑋、陳宏宇、洪銘堅 |
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| 山崩、輸砂量、地震 |
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從1996年賀伯颱風、1999年921地震、2001年桃芝颱風及2004年敏督利颱風等四個事件中的研究發現，土石災害與地質環境有一定必然的關係。在921地震後的五年內，台灣中部地區之陳有蘭溪流域的山崩新生率上升至70%，山崩重現率下降至40%，四個事件之山崩面積機率迴歸指數均大於1.5，此意義顯示土石災害大抵上是以規模小於2000 m2之山崩為主。從集水區內土石災害之最低點的機率分布也可以發現，921地震後仍有超過80%的崩塌材料堆積在山坡上。
從河流輸砂量的統計結果發現，921地震後陳有蘭溪之平均年輸砂量達37百萬噸，較地震前增加13倍，單位懸浮沉積物濃度較地震前增加4 倍以上，此意義顯示，地震後本研究區內的輸砂特性有了變化，不但平均年輸砂量上升，且在相同流量條件下，地震後之輸砂量會較地震前高。
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| Hazardous landslides from 1996 to 2004 in the Chenyoulan River basin of central Taiwan are studied in order to weigh the impact of their controlling factors and to identify their main trigger. The study shows that small landslides contributed a significant proportion of the total area disturbed in the Chenyoulan River basin and that, after earthquakes, > 80% of the landslides remained confined to hillslopes. Rainstorms afterwards can deliver huge hillslope masses into the river, which can lead to a 13-fold increase in average annual sediment discharge. We believe that the landslide effect after earthquakes continues to expand in the understanding that landslide rates continue to rise when rates of newborn landslides display a saturation condition. |
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| THE APPLICATION OF REMOTE SENSING IMAGERY ON THE INTERPRETATION OF DEBRIS FLOW – A CASE STUDY ON BEI-SHIH RIVER, NANTOU |
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| 黃健政、紀宗吉 |
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| 土石流、遙測、北勢溪 |
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土石流常不容易判釋，尢其是高災害強度、低發生頻率者。常聽到人們說：「我在河邊生活一輩子，從未見過發生土石流。」，但經過仔細調查後，常會發現該野溪確曾發生過土石流，因此土石流判釋成為土石流防救災之第一步，也是最重要的一步。
遙測影像判釋可以在室內於短時間內調查廣大面積的土石流，綜觀土石流災害全貌，除了節省龐大的人力、物力外，並大大提升工作效率。一般而言，航照判釋之解析度較高，其應用也較多，唯近來公尺級的衛星影像漸趨普遍，其應用也有日益增加的趨勢。
本研究嚐試探討遙測影像在土石流判釋之應用，並以90年桃芝風災所造成之北勢溪流域土石流災害調查做為研究案例。
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Debris flow hazards are not always easily recognized, particularly on fans that are subject to high magnitude, low-frequency events. Debris flow professionals hear the phrase “I have been living here for so many years and the creek has no debris flow come over the banks”. This statement has often been proven incorrect after detailed investigations. Debris flow hazard recognition is therefore the first, and possibly most important, step in the debris flow hazard analysis.
The remote sensing method has the advantage to investigate vast areas of debris flow events indoor in short time. So it is more cheaper and efficient to evaluate debris flow hazard than other method. In general, stereo aerial photographs is the most common tool for inventories of debris flow due to its higer spatial resolution. Spaceborne multispectral imagers with spatial resolutions of only a few meters have recently been launched, satellite images have become increasingly useful for debris flow delineation.
This paper intend to present the utilization of remote sensing images for recognization, interpretation and analysis of debris-flow. A case study of debris flow triggered by Toraji typhoon in 2001 in Bei-Shih river basin was introduced.
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| INITIATION MECHANISM OF ZONAL DEBRIS FLOWS |
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| 陳榮河、歐泰林 |
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| 土石流、影響因子、發生、機制、模式 |
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土石流之發生有其基本條件及促發條件，基本條件即地質、地文、水文等諸條件，這些條件與地區性有若干的關聯，本文嘗試將歷年研究土石流發生基本條件之成果加以綜合，就花蓮、南投、及台北地區之土石流案例加以分析，以瞭解各區土石流發生的顯著影響因子，期能從中分析出防治的重點。
另外，本文也介紹土石流各種類型，並結合歷年各地區土石材料之力學試驗結果，以一簡化之模式驗證土石流之破壞類型；同時，鑑於土石流之流動特性複雜，數值模式相當繁複，故提出一檢算滑動型土石流之公式，用以評估這類型土石流可能發生之坡度，流動時之速度、加速度，並計算出流動距離等，以利未來土石流影響範圍以及保全對象之訂定，或作為防護工程設計時之參考。
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Initiation of a debris flow depends on basic factors and triggering factors. Basic factors are those of geological, geometrical, and hydrological conditions that are close related to a site condition. In order to correlate the relation, research has been conducted for many years in various zones of Taiwan including the Hualian area in eastern Taiwan, the Nantou area in central Taiwan, and the Taipei area in northern Taiwan. It is hoped to find out significant influential factors for debris flow initiation so that the results can be used for future mitigation.
In addition to that, a simplified model to examine debris flow types is proposed. The parameters used in the model are obtained from many soil tests conducted in the past years. The model has the merits of simplicity, being reasonable accurate, and having physical meaning. It will also provide references for designing preventive structures as well as zoning the area influenced by debris flows.
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| POTENTIAL ANALYSIS AND MITIGATION PRIORITY ASSESSMENT OF POTENTIAL DEBRIS-FLOW TORRENTS |
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| 林美聆、溫惠鈺 |
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| 土石流潛勢溪流、現地調查、潛勢分級、優先處理順序評定 |
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| 台灣特有之地質、地形及氣象條件符合易誘發土石流的要素，故常因颱風豪雨而引致土石流。行政院農委會水土保持局自民國80年起進行土石流潛勢溪流調查，民國85年公佈全省485條土石流潛勢溪流；921地震後增列全省722條土石流潛勢溪流；民國91年桃芝颱風後，完成全省1420條土石流潛勢溪流調查；考量現地地形變遷及各項整治之影響，隨後又於民國92年完成1420條土石流潛勢溪流後續演變觀測。土石流發生條件隨著災害發生而不斷地改變，故需定期辦理土石流潛勢溪流變遷調查，即時更新現地地形地貌及保全對象資料，將現地調查結果建置成為資料庫，並針對其發生潛勢進行分析，同時考慮危害情形加以分析評定，以提供災害防救工作決策支援之依據。本文針對現地土石流潛勢狀況之調查及依據現地調查地形表徵建立土石流潛勢及優先處理順序評定模式。完善之現地調查與潛勢資料分級及土石流處理優先順序評定成果均可用以支持及檢討目前的防災決策，以達到防災的目的，並提供在區域發展和減災管理之進一步應用。 |
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| The geology, topography and meteorological conditions in Taiwan provide the essential condition inducing debris flows. The Soil and Water Conservation Bureau identified 485 potential debris flow torrents in Taiwan in 1996, but the number increased to 1420 after typhoon Toraji in 2001. It appeared that follow-up investigation of the debris flow torrents was required due to variations of topography and other conditions. For such a large number of debris flow torrents, it was also necessary to analyze the occurrence potential as well as to assess the priority of mitigation of the potential torrents in order to provide the decision support for hazard mitigation. In this paper, the field investigation of debris flow torrents and the potential analysis were performed, where the potential analysis was based on the potential factors extracted from ground features documented in the database. Model with risk and mitigation factors was established and then combined with the potential evaluation to provide assessment of mitigation priority. The potential model was tested and adjusted, and the final results were verified using historical events. The potential analysis and final assessment of mitigation priority could be provided as decision supports for drafting of hazard mitigation policy. |
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| RISK ASSESSMENT AND DISASTER MANAGEMENT FOR DEBRIS-FLOW HAZARD ZONES |
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| 陳樹群、馮智偉、吳俊毅、黃柏璁、王价巨 |
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| 風險評估、危害度評估、易致災性分析、承受度評估、風險地圖 |
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| 本文研究土石流潛勢溪流風險評估之方法。土石流風險評估包含土石流危害度評估、易致災性分析及承受度評估等三部分。危害度評估可藉由蝕溝密度、坡面15度以上之集水區面積、集水區高差、崩塌面積比及主流長度等因子來評估；易致災性部分則以土地利用類別來評估遭受危害時可能造成之相對損失；承受度方面則藉由問卷設計、隨機訪談的方式，試圖就居民防災意識素養評估其對於土石流危害的承受度，期使能呈現出該地承受度分布狀況。綜合以上三者後再輔以ArcView軟體，分析並呈現出該地之風險地圖，可做為風險管理決策之參考。因此，本研究即依循風險評估之架構，分別介紹土石流危害度評估、易致災性分析以及承受度評估之方法，藉由台中縣和平鄉博愛村之案例藉以說明土石流風險評估之方法。 |
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| The purpose of this paper is to establish a method for assessing the risk of debris flow hazard-prone streams. Debris flow risk assessment comprises hazard assessment, vulnerability analysis and capacity assessment. Firstly, hazard assessment can be estimated from gully density, basin areas with slope larger than 15 degree, basin relief, landslide ratio and mainstream length. For the vulnerability analysis, this research estimates the possible loss based on the type of land use. In order to assess the capacity of a community, the questionnaires and interviews of the residents were processed randomly in the hazard-prone areas to learn the way they cope with debris flow hazards. Finally, for the references of decision-making for risk management, the risk maps were producing by ArcView GIS software. In addition, a village, Bo-Ai in Taichung Counties was taken as examples to explain the analysis procedure. |
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| A RAINFALL-BASED DEBRIS-FLOW SPATIAL AND TEMPORAL WARNING MODEL |
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| 詹錢登、李明熹、郭峰豪 |
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| 土石流、降雨驅動指標、邏輯斯迴歸分析、空間及時間警戒 |
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| 本文分析過去誘發土石流的降雨資料，計算土石流發生事件的降雨強度及有效累積雨量，並以降雨強度及有效累積雨量的乘積作為降雨驅動指標(RTI )，進而建立土石流發生降雨警戒值，然後以邏輯斯迴歸分析，建立土石流發生各種不同可能性條件下所對應之降雨驅動指標警戒值(RTIp)。以南投縣信義鄉及仁愛鄉為驗證對象，以南投地區7個鄉鎮為應用對象，結果顯示本文所發展的模式能有效呈現降雨過程中不同時間之土石流發生可能性之空間及時間警戒變化情形。 |
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| The data of rainfall events that induced debris flows were analyzed to calculate the corresponding rainfall intensities, effective accumulated rainfall amounts, as well as the values of rainfall triggering index (RTI ) defined as the product of the rainfall intensity multiplied by the effective accumulated rainfall amount, and then to evaluate the spatial distribution of the critical RTI -values for debris-flow warning. The logistic regression method was used to evaluate the potential distribution of debris-flow occurrence, based on the corresponding RTI -values of debris flow events. The proposed model was tested during two rainfall events at Sinyi Town and Ren-ai Town in Nantou County of Central Taiwan, and then applied to evaluate the temporal variations of debris-flow occurrence probabilities for seven towns in Nantou County. The results show that the proposed model could effectively evaluate the spatial and temporal variations of debris-flow occurrence probability during a rainfall event. |
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| THE PRESENT DEVELOPMENT OF DEBRIS FLOW MONITORING TECHNOLOGY IN TAIWAN |
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| 尹孝元、黃清哲、李秉乾、連榮吉 |
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| 土石流觀測站、模組化、土石流防災應變系統 |
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| 本文主要針對行政院農業委員會水土保持局建置的土石流觀測站相關研發技術進行深入的探討。水土保持局自2002年起開始進行土石流現場觀測工作，最初在土石流潛勢溪流現場以建置固定式土石流觀測站為主，期間為了提升現場土石流事件捕捉率、擴大觀測範圍及降低儀器故障率，同時積極投入行動式土石流觀測站及觀測系統模組化的研發工作，行動式土石流觀測站主要可機動派遣至颱風預測路徑上土石流發生潛勢較高的地點進行現場土石流觀測任務，而模組化系統則可大幅降低整體維運成本並提升現場觀測效能，至目前為止水土保持局已完成13座固定式及2組行動式土石流觀測站，各站主要架構可分為觀測儀器、現場儀器屋(行動站為車裝儀器平台)、資料傳輸系統及後端資料處理展示系統(土石流防災應變系統，http://fema.swcb.gov.tw)四大部分。土石流觀測站設置目的為蒐集本土化之現場土石流觀測資料，瞭解土石流運動過程中各項行為機制，除了可提昇現行以雨量為指標的土石流警戒模式精確度，亦可提供防砂工程設計、應變措施擬定及學術研究的參考。 |
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| This paper introduces the up to date technology of debris flow monitoring stations established by the Soil and Water Conservation Bureau, Council of Agriculture (SWCB). Besides constructing the fixed debris flow monitoring stations, the SWCB also performs the research on the mobilization and module of debris flow monitoring system in order to enhance the monitoring possibility of debris flow events, to reduce the damage of the on-the-spot instruments and to broaden the monitoring limitation. The mobile debris flow monitoring station can be immediately sent to the high potential spot to detect the possible debris flow events according to the prediction route of incoming typhoon from Central Weather Bureau. The module of the debris flow monitoring system may play an important role in decreasing the maintenance cost and increasing the monitoring efficiency due to the portable devices. So far, the SWCB establishes 13 fixed and 2 mobile debris flow monitoring stations around Taiwan. Each station consists of the monitoring sensors, the instrumental cabin (mobile instrument plate for mobile monitoring station), the transmission system and the display system (Formosa Emergency Management Action system, http://fema.swcb.gov.tw). The purpose of setting up these monitoring stations are to collect real-time debris flow information in the field. This information may help us to understand the physical mechanism of debris flows and to improve the accuracy of the current debris flow warning system based on rainfall thresholds. Besides, it also can be utilized as references for sabo engineering design, countermeasures of slopeland disaster mitigation and academic research. |
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| DESIGN CONCEPT AND COUNTERMEASURES FOR DEBRIS-FLOW MITIGATION |
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| 吳嘉俊 |
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| 土石流防治、土石流防治工法 |
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| 土石流由於發生頻率的不確定、規模大小的不可測，使得土石流的防治及相關的因應工法在設計思維上無法以制式的方式套用在不同的地點，主動式與被動式防治工法的調配運用，工程設計人員對於土石流防治觀念的靈活應用，以及以安全為基礎但又兼具生態棲地維護甚至多功能空間發揮的巧思，是本論文討論的主軸。本文的主要目的在於觀念的傳達，不在於設計的規定，如何靈活融入仍需要工程先進多費心思。 |
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| The Uncertainty of reoccurrence frequency and the unpredictability of the event scale make debris-flow mitigation and countermeasure techniques less standardized as we anticipate. Engineers are required to adapt the concepts of active and passive defense system to cope with specific debris-flow cases so that safety concern is fulfilled and ecologic habitats are maintained. The main objective of this paper is to convey the design concept and rational of debris-flow countermeasures. Setting design standards or recommendations is not the intention of the paper. |
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| IMPACT OF CHI-CHI EARTHQUAKE ON THE OCCURRENCE OF DEBRIS FLOWS: EXAMPLE FROM THE DA-CHIA RIVER WATERSHED |
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| 顧承宇、鄭錦桐、冀樹勇、余勝雄、楊勳得 焦中輝 |
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| 集集地震、土石流、土石流降雨量、遙測資料、土砂產量 |
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| 本文針對大甲溪流域德基壩至馬鞍壩之間主要災害區域之土石流問題進行廣泛之現地調查，並透過集集地震前(88/04/01)、集集地震後(88/10/31)、桃芝颱風後(90/11/18)、敏督利颱風後(93/07/21)、與艾利及海棠颱風後(95/02/21)等時期之衛星影像、航照影像、數值地形模型、及雨量資料進行區域土石流特性與成因之詳細分析。成果顯示，集集地震造成廣泛之崩塌面積與龐大之崩塌土石料源，應是造成大甲溪流域崩塌及土石流災害之主因。惟集集地震後初期堆積於集水區內之大量土砂多成點狀分布於集水區內，但地震後數次之颱風豪雨加速土石崩落與土砂往下游運移，造成原「點狀」分布之崩塌土砂材料經由豪雨運移集中至大甲溪主支流中，形成「網絡狀」之土砂分布，進而造成各支流及野溪嚴重之土石流問題。另暴雨所導致之崩塌與後續土石流發生均集中於德基壩與馬鞍壩之間，此現象與大甲溪流域之降雨空間分布特性亦有強烈之關聯性。 |
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| This paper presents the study on the occurrence of debris flows from the Da-Chia river watershed after Chi-Chi earthquake through the use of remote sensing data, DEM, and rainfall data. The remote sensing data include aerial photographs and satellite images of five temporal stages which are the stage before Chi-Chi earthquake, the stage after Chi-Chi earthquake, the stage after typhoon Toraji, the stage after typhoon Minduli, the stage after typhoon Airi and Hytarng. Results obtained show that the regional debris flow problems in Da-Chia watershed were mainly caused by the huge amount of sparsely deposited materials from landslides triggered by Chi-Chi earthquake. Several typhoon events with heavy rainfalls moved the sparsely deposited materials into gullies and then induced the debris flows. It is also demonstrated that the regional debris flows that range from Techi Dam to Ma-an Dam are strong related to the spatial distribution of rainfalls. |
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| CASE STUDY ON REMEDIATION CONSTRUCTION DESIGN OF DEBRIS FLOW IN SITOU NATURE EDUCATION AREA |
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| 陳福勝、吳文隆、楊智堯 |
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| 溪頭、土石流、集集地震、桃芝颱風、整治工程 |
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| 台灣位於歐亞板塊與菲律賓海板塊交界處，地質活動頻繁，地層年代輕且破碎，地質構造複雜，加上地震以及豪大雨，所引發之山崩、地滑及土石流實乃為台灣之天然災害。惟近年來，隨著經濟快速發展以及生活空間的需求，人類之活動範圍已由平原逐漸擴大到山區，尤其常見以河谷及沖積扇為聚落群聚之處，因此土石流對其造成危害甚巨。本文以土石流災害之特性來作為防治與整治工法之設計探討，並以溪頭自教育園區之災害整治案例，進行土石流災害整治工程流程之完整說明與介紹，提供國內進行土石流災害整治工程之參考。 |
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| The geological structures of Taiwan are complex, weak and young. The rock slopes of many river valleys were damaged by earthquakes and landslides, which caused a great deal of cracks and unstable rock blocks. The torrential rain brought by typhoons usually induced serious debris flow. In the recent years, with the increasing of population density and the development of economy, the scope of human activity has been expanded to the mountain district. For the reason, debris flow disaster has been the nightmare of us. This paper presents the case of remediation construction in Sitou. And with the presentation, it is advantage to the engineers to take the lessons as a reference in their plan, design, and construction works to against the disasters |
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