• Title/Summary/Keyword: Rainfall and Flood

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Estimation of initial abstraction to calculate effective rainfall by considering soil moisture content in watershed (유역 토양 수분량을 고려한 초기손실 추정)

  • Lee, Jung-Sun;Lee, Dong-Hyun;Kim, Tai-Cheol
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2002.10a
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    • pp.245-248
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    • 2002
  • The Soil Conservation Service (SCS) developed a unique procedure for estimating direct runoff from storm rainfall. But, It is very difficult to estimate accurately flood hydrograph by SCS method, because the initial ion of Ia(0.2Sa) itself has lots of systematic errors and there is no investigation on Ia in the Korean watershed. The maximum storage capacity of Umax is calibrated in the DAWAST model and is related to the present ability of rainfall to be infiltrated into the unsaturated soil. Effective rainfall for design and real-time flood hydrograph can be estimate more reasonably by introducing new Ia relationship made from the rainfall-runoff data observed in the Korean watersheds.

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Determination of the Storage Constant for the Clark Model by based on the Observed Rainfall-Runoff Data (강우-유출 자료에 의한 Clark 모형의 저류상수 결정)

  • Ahn, Tae-Jin;Choi, Kwang-Hoon
    • Proceedings of the Korea Water Resources Association Conference
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    • 2007.05a
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    • pp.1454-1458
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    • 2007
  • The determination of feasible design flood is the most important to control flood damage in river management. Model parameters should be calibrated using observed discharge but due to deficiency of observed data the parameters have been adopted by engineer's empirical sense. Storage constant in the Clark unit hydrograph method mainly affects magnitude of peak flood. This study is to estimate the storage constant based on the observed rainfall-runoff data at the three stage stations in the Imjin river basin and the three stage stations in the Ansung river basin. In this study four methods have been proposed to estimate the storage constant from observed rainfall-runoff data. The HEC-HMS model has been adopted to execute the sensitivity of storage constant. A criteria has been proposed to determine storage constant based on the results of the observed hydrograph and the HEC-HMS model.

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A Study on Flash Flood Warning in Mountainous Area (산악지역 돌발홍수 경보발령 기준 설정에 관한 연구)

  • Jun, Kye-Won;Oh, Chae-Yeon;Yeon, Gyu-Bang;Lee, Seung-Chul;Jun, Byong-Hee
    • 한국방재학회:학술대회논문집
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    • 2007.02a
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    • pp.591-594
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    • 2007
  • The purpose of this study is to estimate the critical flood discharge and flash flood trigger rainfall for alarm system providing for a flash flood in mountainous. This study was effectively estimated a topographic characteristic factor of basin using the GIS. Especially, decided stream order using GIS at stream order decision that is important for input variable of GCIUH. Result that calculate threshold discharge to use GCIUH, at the Mureung valley basin, flash flood trigger rainfall was 16.34mm in the first 20 minutes when the threshold discharge was $14.54\;m^3/sec$.

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Estimation of the Flash Flood Severity using Flash Flood Index (돌발홍수지수를 이용한 돌발홍수심도 산정)

  • Kim, Eung-Seok;Choi, Hyun-Il;Lee, Dong-Eui;Kang, Dong-Jin
    • Journal of the Korean Society of Hazard Mitigation
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    • v.9 no.6
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    • pp.125-131
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    • 2009
  • The aim of this study is to quantify the severity of flash food for a study watershed in Korea by estimation of flash food index using flood runoff hydrograph following Bhaskar et. al (2000). As an extension of the previous research, we examine the relation between flash food index and rainfall intensity, rainfall duration, and total runoff, respectively. This study has estimated the flash food index through simulated flood hydrographs to investigate the relative severity of flash flood in an ungauged basin, Megok river basin for 31 flood events.

A Case Study on Development of Stormwater Retention and Infiltration Pond System (우수저류 및 침투연못 시스템개발 사례연구 - 우수 저류 및 침투 효과를 중심으로 -)

  • Lee, Jae Chul;Yoon, Yeo Jin
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.6 no.4
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    • pp.52-61
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    • 2003
  • This study was carried out to analyze the effects of stormwater retention and infiltration pond on reduction of flood peak and volume in a experimentally developed ecological pond. The experimental site has 542$m^2$ watershed area, 1,310mm yearly-averaged rainfall. And the area of the retention pond is 60$m^2$, the maximum water depth is 0.5m, the maximum and average storage is 15$m^3$and 9.3$m^3$d. And the area of infiltration pond is 58$m^2$, and the water depth varies 0.2m~0.5m. The monitoring system consists of one rainfall gage, one Parshall flume and acoustic water level gage, two rectangular weirs and acoustic water level gage for discharge gaging, and one data recording unit. Data from ten storm events in total, three storm events in year 2000 and seven storm events in year 2001, were collected. From the data the evaporation rate was achieved with the water balance equation, and the result shows 5.0mm/day in average. The result from the analysis of the effects on reduction of flood peak and volume, is that 14% reduction of flood volume and 15% reduction of flood peak in retention pond and 49% reduction of flood volume in infiltration pond.

Analysis of Flood Control Capacity of Agricultural Reservoir Based on SSP Climate Change Scenario (SSP 기후변화 시나리오에 따른 농업용 저수지 홍수조절능력 분석)

  • Kim, Jihye;Kwak, Jihye;Hwang, Soonho;Jun, Sang Min;Lee, Sunghack;Lee, Jae Nam;Kang, Moon Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.63 no.5
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    • pp.49-62
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    • 2021
  • The objective of this study was to evaluate the flood control capacity of the agricultural reservoir based on state-of-the-art climate change scenario - SSP (Shared Socioeconomic Pathways). 18 agricultural reservoirs were selected as the study sites, and future rainfall data based on SSP scenario provided by CMIP6 (Coupled Model Intercomparison Project 6) was applied to analyze the impact of climate change. The frequency analysis module, the rainfall-runoff module, the reservoir operation module, and their linkage system were built and applied to simulate probable rainfall, maximum inflow, maximum outflow, and maximum water level of the reservoirs. And the maximum values were compared with the design values, such as design flood of reservoirs, design flood of direct downstream, and top of dam elevation, respectively. According to whether or not the maximum values exceed each design value, cases were divided into eight categories; I-O-H, I-O, I-H, I, O-H, O, H, X. Probable rainfall (200-yr frequency, 12-h duration) for observed data (1973~2020) was a maximum of 445.2 mm and increased to 619.1~1,359.7 mm in the future (2011~2100). For the present, 61.1% of the reservoirs corresponded to I-O, which means the reservoirs have sufficient capacity to discharge large inflow; however, there is a risk of overflowing downstream due to excessive outflow. For the future, six reservoirs (Idong, Baekgok, Yedang, Tapjung, Naju, Jangsung) were changed from I-O to I-O-H, which means inflow increases beyond the discharge capacity due to climate change, and there is a risk of collapse due to dam overflow.

Floods and Flood Warning in New Zealand

  • Doyle, Martin
    • Proceedings of the Korea Water Resources Association Conference
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    • 2012.05a
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    • pp.20-25
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    • 2012
  • New Zealand suffers from regular floods, these being the most common source of insurance claims for damage from natural hazard events in the country. This paper describes the origin and distribution of the largest floods in New Zealand, and describes the systems used to monitor and predict floods. In New Zealand, broad-scale heavy rainfall (and flooding), is the result of warm moist air flowing out from the tropics into the mid-latitudes. There is no monsoon in New Zealand. The terrain has a substantial influence on the distribution of rainfall, with the largest annual totals occurring near the South Island's Southern Alps, the highest mountains in the country. The orographic effect here is extreme, with 3km of elevation gained over a 20km distance from the coast. Across New Zealand, short duration high intensity rainfall from thunderstorms also causes flooding in urban areas and small catchments. Forecasts of severe weather are provided by the New Zealand MetService, a Government owned company. MetService uses global weather models and a number of limited-area weather models to provide warnings and data streams of predicted rainfall to local Councils. Flood monitoring, prediction and warning are carried out by 16 local Councils. All Councils collect their own rainfall and river flow data, and a variety of prediction methods are utilized. These range from experienced staff making intuitive decisions based on previous effects of heavy rain, to hydrological models linked to outputs from MetService weather prediction models. No operational hydrological models are linked to weather radar in New Zealand. Councils provide warnings to Civil Defence Emergency Management, and also directly to farmers and other occupiers of flood prone areas. Warnings are distributed by email, text message and automated voice systems. A nation-wide hydrological model is also operated by NIWA, a Government-owned research institute. It is linked to a single high resolution weather model which runs on a super computer. The NIWA model does not provide public forecasts. The rivers with the greatest flood flows are shown, and these are ranked in terms of peak specific discharge. It can be seen that of the largest floods occur on the West Coast of the South Island, and the greatest flows per unit area are also found in this location.

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Inundating Disaster Assessment in Coastal Areas Using Urban Flood Model (도시홍수모델을 이용한 해안지역의 침수재해평가)

  • Yoo Hwan-Hee;Kim Weon-Seok;Kim Seong-Sam
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.24 no.3
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    • pp.299-309
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    • 2006
  • In recent years, a large natural disasters have occurred due to worldwide abnormal weather and the amount of damage has been increased more resulting from high density population and a large-sized buildings of the urbanized area. In this study. we estimate the flooded area according to rainfall probability intensify and sea level in Woreong dong, Masan occurred flood damages by typhoon Maemi using SWMM, a dynamic rainfall-runoff simulation model in urban area, and then analyze the damage of flood expected area through connecting with GIS database. In result, we can predict accurately expected area of inundation according to the rainfall intensity and sea level rise through dividing the study area into sub-area and estimating a flooded area and height using SWMM. We provide also the shelter information available for urban planning and flood risk estimation by landuse in expected flood area. Further research for hazard management system construction linked with web or wireless communication technology expects to increase its application.

Performance analysis of flood prevention projects through flood simulation (침수 시뮬레이션을 통한 침수예방사업의 성과분석)

  • Shin, Jungsub;Chung, Seokhyun;Cho, Byoungog;Kang, Seonhong;Park, Byungman;Yoon, Joonjae
    • Journal of Korean Society of Water and Wastewater
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    • v.32 no.2
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    • pp.169-181
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    • 2018
  • For performance analysis of flood prevention projects, this study performed simulation (SWMM) for the five sites where the projects have been completed. The models were constructed using watershed and sewer information of the project sites and were verified using flood records in the past to improve accuracy. In this simulation, the design rainfall data (probability 30~50 years) and the rainfall data in the summer of 2017 were applied. When the design rainfall data was applied to the models, simulation results presented that all the sites were flooded before the projects, but after the projects all the sites were not flooded due to improve discharge capacity. And when the rainfall data in the summer of 2017 was applied to the models, simulation results presented that all the sites were flooded before the projects, but after the projects any sites did not occur flooding in this summer. So if the projects had not been completed, all the sites might be flooded in the summer of 2017. These effects were analyzed as the improvement of discharge capacity due to rehabilitation of sewer, construction of underground tunnel and pumping station, etc. As the results, ratio of sewer that water depth exceed diameter reduced from 52.3~75.8% to 17.1~39.8%.

Development of Urban Flood Warning System Using Regression Analysis (회귀분석에 의한 도시홍수 예보시스템의 개발)

  • Lee, BeumHee
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.4B
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    • pp.347-359
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    • 2010
  • A simple web-based flood forecasting system using data from stage and rainfall monitoring stations was developed to solve the difficulty that real-time forecasting model could not get the reliabilities because of assumption of future rainfall duration and intensity. The regression model in this research could forecast future water level of maximum 2 hours after using data from stage and rainfall monitoring stations in Daejeon area. Real time stage and rainfall data were transformed from web-sites of Geum River Flood Control Office & Han River Flood Control Office based MS-Excel 2007. It showed stable forecasts by its maximum standard deviation of 5 cm, means of 1~4 cm and most of improved coefficient of determinations were over 0.95. It showed also more researches about the stationarity of watershed and time-series approach are necessary.