Development of Flash-Flood Warning System Considering Watersheds with Different Geo-Hydrological Characteristics

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Project title

Code/計畫編號

MOST103-2923-E019-001-MY3

Translated Name/計畫中文名

建立適用於不同地文與水文特性集水區之迅洪預警系統

Project Coordinator/計畫主持人

Kwan-Tun Lee

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Harbor and River Engineering

Website

https://www.grb.gov.tw/search/planDetail?id=8111677

Year

2014

Start date/計畫起

01-01-2014

Expected Completion/計畫迄

31-12-2014

Bugetid/研究經費

600千元

ResearchField/研究領域

土木水利工程
防災工程

"由於近十年受到全球氣候變遷效應的影響，水文異常現象發生頻率增高，災害規模亦有加劇的趨勢，除了重新檢視防洪設計標準之外，工程師對於超過工程保護標準之極端降雨條件必須備有因應對策，進而評估洪災事件可能帶來的生命財產損失。近年來發生甚為頻繁之高強度暴雨事件以及山區雪地、冰川的快速融化已導致北高加索地區、俄羅斯遠東地區以及台灣全島經常遭受洪災之威脅，因此洪災預警系統之建置乃為當急之要務。一般建立汛洪預警系統的標準程序包含水文氣象資料的量測與傳輸、資料庫的管理、降雨預測、逕流估計以及預測結果的即時發佈；而本計畫之研究內容將著重於水文模式的開發與建置，以設法應用於洪災之預警。共同參與本計畫之台灣與俄羅斯研究團隊將針對模式之建立以及水文量測技術進行雙方經驗之交流。本計畫預計開發之水文模式包含(1)集水區降雨逕流模式；(2)河道演算模式；(3)二維淹水模式，以及(4)溢堤水流計算模式。考量以上模組於實務操作上之便利性，主要採用簡化且較為可靠之方式，以作為模式建置之概念基礎，並且設法建立一可反應集水區地文與水文特性的汛洪預警系統。本計畫於三年的執行期間，研究工作之主要內容及項目如下所述：第一年：研究工作將著重於集水區降雨逕流模式之發展，以及建置可考量渠網連結之一維河道演算模式。研究中將利用集水區地貌特性，以及流域內不同流徑所組成之集流時間以進行逕流量之推估；而於河道演算中，為避免地勢或流況轉變所導致之數值發散問題，研究中將合併使用簡化運動波與完整動力波理論，並配合不同數值演算方式，以模擬洪水波於河道運移之情形。第二年：將發展以擴散波理論為基礎之全分佈式二維淹水模式，藉以描述水流於流域內之傳遞情形並進而估算格點之浸淹深度。此外，該逕流演算模式將與第一年計畫所開發之河道演算模式相互銜接，以建立整合渠流與漫地流演算之淹水模式，研究中將設法解決兩演算模式與水流交換過程中，所遭遇之數值振盪問題，並採用溢流堰公式建立渠流溢堤機制，以估算河道水位高過於堤頂高程情況下之溢流損失量。第三年：擬將前兩年計畫所建置之河道演算模式、二維淹水模式以及溢堤水流計算模式，實際應用於台灣與俄羅斯兩地之集水區，以進行數值模擬測試，並收集流域之水文紀錄資料，設法評估並驗證研究中所開發之模式的適用性。本三年期國際合作計畫將初步建立一淹水預警模式於台俄兩集水區中，並針對模擬結果進行比較分析。考量都市人口密集地區於汛洪時期可能蒙受鉅額的經濟損失，農業灌區若遭受洪水短期浸淹，其損失相對地較為輕微，因此若能妥善規劃都市周邊或是中上游之農業區域及荒地，以作為短期滯洪蓄水之用，則可望降低下游都市地區溢淹之威脅。因此，研究中擬利用所發展之淹水模式，並藉由地理資訊系統選取符合地勢條件之滯洪區域，以進行模擬分析與效能評估。本國際合作計畫中，台俄雙方學者之合作包括地文與水文資料之交換、模式建立之經驗交流以及討論研習。本計畫之研究成果將有助於相關單位，於汛洪時期擬定合適之防洪減災措施。 " "In recent years, global climate change has resulted in frequently hydrological disasters and exacerbated the extent of damage. Consequently, engineering measurement should be conceived in advance for severe disaster induced by extreme weather conditions. The flash flood results from high intensity rainstorms including quick melting supply of snow or glacier in mountain areas. Flash floods can be found in North Caucasus and Far East of Russia, and occur within the whole island of Taiwan. Standard practice in a flash-flood warning system includes hydro-meteorological measured data transmission, database management, rainfall prediction, runoff estimation, and forecasting information dissemination. In this project, we focus on hydrological model developing for the flood warning system. Experiences from Taiwan and Russian teams in hydrological modeling and field measurement techniques will exchange. Hydrological simulation models developed in this study will include: (1) watershed rainfall-runoff model, (2) channel-flow routing model, (3) two-dimensional inundation model, and (4) overbank-flow estimation model. The models should satisfy to following conditions: to be simple and reliable enough for using in operational practice; to cover all main prediction tasks along the flash flood wave generation and propagation; and to reflect different geo-hydrological characteristics of the watershed. The project will be conducted for three years. The contents of the research work are listed as follows: First year: The study work will be focused on developing a watershed rainfall-runoff model and a one-dimensional channel-flow routing model considering stream network. The watershed runoff model is based on the analysis of watershed geomorphologic characteristics and flow-travel-time estimation through different runoff paths. Numerical algorithms will be developed using dynamic-wave and kinematic-wave approaches to account for watershed with different geo-hydrological characteristics. Floodwater transport in the stream network system will also be considered. Second year: A two-dimensional inundation model based on diffusion-wave approach will be developed. The inundation model will be linked to the channel-flow routing model and further included overbank-flow mechanism to estimate the outflow discharge hydrograph while the flood stage is higher than the levee height. The volume of floodwater flowing from channel to nearby overland areas is then estimated, and information for the flooding extent and water depth will be provided for evacuation. The research work will also focus on investigating the numerical instability of floodwater distributed onto the near bank low lying areas. Third year: The channel-flow routing model, two-dimensional inundation model, and overbank-flow estimation model will be tested in the selected watersheds of Taiwan and Russia (North Caucasus and Far East) to realize the capability and limitation of the models. Hydrological records and digital elevation dataset from the watersheds will be used to verify the applicability of the developed models. A preliminary version of the inundation warning system will be built in the two example watersheds to confirm the result of the joint research project. Since flooding losses in urban areas is significantly higher than that in rural areas, it can be expected that the hazard can be mitigated by draining the floodwater into unpopulated rural areas. Consequently, possible flood storage areas to alleviate downtown flooding in the example watersheds will also be proposed by examining the hydrological modeling results and the topographic characteristics of the watersheds using the geographic information system (GIS) techniques. This joint research cooperation between Taiwan and Russian scientists includes research consultations, data interchange, and probation trainings in both countries. It intends to provide valuable information for authorities on disaster mitigation during severe rainstorms. "

Keyword(s)

降雨逕流模式
河道演算模式
二維淹水模式
溢堤水流
watershed rainfall-runoff model
channel-flow routing model
2D inundation model
overbank flow.

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Development of Flash-Flood Warning System Considering Watersheds with Different Geo-Hydrological Characteristics

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