Rainfall-runoff Analysis Research Articles

Effect of Rainfall Temporal Distribution on the Conversion Factor to Convert the Fixed-Interval into True-Interval Rainfall

AbstractIn this study, the Weiss approach to derive the CF (the conversion factor to convert the fixed-interval annual maximum rainfall into the true-interval one) was examined and revised to consider the rainfall temporal distribution. As examples, several rainfall temporal distribution models currently being used in the rainfall-runoff analysis, along with several simple distributions such as triangular or pentagonal, were considered to derive the CF. The resulting CFs were then compared with the CFs estimated by analyzing the observed rainfall data, both in Korea and in several other countries, such as the United States, the United Kingdom, Australia, and New Zealand. The findings from this study can be summarized as follows. First, the effect of the temporal distribution of rainfall is very significant on the estimation of the CF. The CF for the impulse rainfall was the smallest at 1.0, and that for the uniformly-distributed rainfall was the highest at 1.333. Second, the CFs derived for the temporal d...

分布型流出モデルと時空間起源追跡法による鬼怒川洪水の流出解析

分布型流出モデルと時空間起源追跡法による鬼怒川洪水の流出解析

Automated hydrologic analysis of ungauged basins in Serbia using open source software

Drainage basins are for the most part ungauged or poorly gauged not only in Serbia but in most parts of the world, usually due to insufficient funds, but also the decommission of river gauges in upland catchments to focus on downstream areas which are more populated. Design discharges are needed for these rivers where no streamflow data are available, for various applications. Examples include river training works for flood protection measures or erosion control, design of culverts, water supply facilities, small hydropower plants, etc. This study deals with the application of freely available and open source software and datasets for automating rainfall–runoff analysis of ungauged basins, applying geographical information systems techniques and programming to methodologies currently in use in hydrological practice. The geomorphometric module was tested on more than 100 catchments throughout Serbia (using a digital terrain model) and compared to manually calculated values (using topographic maps). The discharge estimation module was tested on 21 catchments where data were available and compared to results obtained by frequency analysis of measured discharges. The geomorphometric module of the calculation system showed excellent results, saving a great deal of time that would otherwise have been spent on manual processing of geospatial data, while the discharge estimation module showed a need for improved hydrological models.

Multi‐site calibration using a grid‐based event rainfall–runoff model: a case study of the upstream areas of the Nakdong River basin in Korea

AbstractMost runoff analyses using a grid‐based distributed model use one parameter group calibrated at the outlet of a watershed, instead of dividing the watershed into subwatersheds. Significant differences between the observed value and the simulation result of the subwatersheds can occur if just one parameter group is used in all subwatersheds that have different hydrological characteristics from each other. Therefore, to improve the simulation results of the subwatersheds within a watershed, a model calibrated at every subwatershed needs to be used to reflect the characteristics of each subwatershed. In this study, different parameter groups were set up for one or two sites using a distributed model, the GRM (Grid based Rainfall‐runoff Model), and the evaluations were based on the results of rainfall–runoff analysis, which uses a multi‐site calibration (MSC) technique to calibrate the model at the outlet of each site. The Hyangseok watershed in Naeseong River, which is a tributary of Nakdong River in Korea, was chosen as the study area. The watershed was divided into five subwatersheds each with a subwatershed outlet that was applied to the calibration sites. The MSC was applied for five cases. When a site was added for calibration in a watershed, the runoff simulation showed better results than the calibration of only one site at the most downstream area of the watershed. The MSC approach could improve the simulation results on the calibrated sites and even on the non‐calibrated sites, and the effect of MSC was improved when the calibrated site was closer to the runoff site. Copyright © 2014 John Wiley & Sons, Ltd.

Estimating the 100-year Peak Flow for Ungagged Middle Creek Watershed in Northern California, USA

This study presents a case study for estimating the 100-year peak flow for Middle Creek Watershed in Northern California. The watershed contains several stream flow gages; however, the precipitation data is only available as daily data, which was not usable form for this study. Thus considering that the watershed to be ungagged. In order to overcome this shortcoming in the hydrologic analysis, other approaches were considered. Therefore, the precipitation point frequency estimates were obtained from the National Oceanic and Atmospheric Administration (NOAA) Atlas 14. The Hydrologic Engineering Center’s Hydrologic Modeling System (HMS) was used to create the hydrologic model to estimate the peak flows at key points in the watershed. The purpose of using the HMS model was to predict eh rainfall-runoff analysis for this watershed, which only has steam gage data. Other parameters needed for the HMS model were obtained from various sources as suggested in the United States Army Corps of Engineers (USACE) Central Valley Hydrology Study (CVHS): Technical procedures document. The 100-year flows from the HMS model results were then calibrated/validated by comparing to the 100-year flow frequency curves computed using the Hydrologic Engineering Center’s Flood Frequency Analysis (FFA) program, FEMA USACE, and USGS Regression methods. Sensitivity analysis of several of the model parameters was analyzed to determine the results confidence level. The HMS modeled results were in good agreement with the results obtained from the Flood Frequency method and the USGS regression studies. The procedure described herein for developing and validating hydrologic models for ungagged watersheds can be used for other similar ungagged watersheds.

다목적 최적화 기법을 이용한 수위관측망 평가

본 연구에서는 남강댐 유역을 대상으로 수위관측소의 수문정보량과 설치목적별 중요도를 고려하여 수위관측망을 평가하였다. 엔트로피 이론을 적용하여 산정된 수문정보량과 설치목적별 중요도를 동시에 고려하기 위해 유클리디언 거리를 이용하여 2개의 목적함수를 통합하였으며, 이를 다목적 최적화 기법을 이용하여 최적관측망을 선정하였다. 최적 수위관측망을 구축하기 위해 대표단위도를 실제 강우-유출 해석을 결과를 바탕으로 유도한 후 확률밀도함수로의 전이를 통해 엔트로피 이론에 적용하였다. 아울러 설치목적별 중요도는 MLIT(2010)에서 조사한 수위관측소별 설치목적을 참조하여 등급을 정량화 하였다. 이를 남강댐에 유역에 적용한 결과 다목적 최적화 기법을 이용하여 수위관측망을 평가한 경우가 엔트로피 이론만을 적용했을 때보다 관측소의 설치목적을 보다 잘 만족함을 확인하였다. 이는 수위관측소의 설치목적별 중요도와 자료의 특성이 동시에 반영된 결과이다. 아울러 대상유역인 남강댐 유역에서는 총 12개의 수위관측소 중 8개의 수위관측소가 필요한 것으로 판단된다. This study has evaluated the stream gauge network which is considered the total hydrological information and the importance class of stream gauge stations, and is applied to Namgang Dam basin. The total hydrological information and the importance class of stream gauge stations are two different physical parameters. We adopt the Euclidean distance method to consider them simultaneously. An equation obtained by the Euclidean distance method is used as the objective function in multiobjective optimization method to determine the optimal combination of the stream gauge stations for satisfying the both criteria: the maximum total amount of the hydrological information and the importance class of stream gauge stations. To evaluate the optimal stream gauge network, the representative unit hydrograph which is derived by real rainfall-runoff analysis is transferred into probability density function for the application of entropy theory concept. The importance class of stream gauge stations is determined by referring the result of MLIT (2010). As result of applying to Namgang Dam basin, The optimal stream gauge network obtained by the suggested method shows more satisfied the importance of stream gauge station purpose than the optimal stream gauge network obtain by the entropy theory only. This result implies that the optimal steam gauge network by the suggested method can consider both the total hydrological information and the importance class of stream gauge station. It is found that Namgang Dam basin needs at least 8 steam gauge stations among 12 steam gauge stations.

Effectiveness of Ubol Ratana and Lam Pao Reservoirs for Flood Mitigation in the Downstream Area of the Chi River Basin Using HEC-HMS Model

The Chi River Basin is vulnerable to flooding due to its location in the pathway of tropical storms during the monsoon season, flat topography, large proportion area of community settlements and agricultural activities and poor management of water release from dams. Since there is still a lack of lasting viable solution to flooding problems, an insight into detailed aspects of flood alleviation needs to be addressed. The objective of this study was to perform rainfall-runoff analysis using Hydrologic Modelling System (HEC-HMS) model in order to assess the effectiveness of Ubol Ratana and Lam Pao reservoirs for flood mitigation in the downstream area of the Chi River Basin. A scenario-based study that investigates the attenuation of flood peak discharge downstream of the Chi River Basin for the year 2001 was presented. Water storing and releasing scenarios from different reservoirs were designed to cover possible situations. The HEC-HMS model was used to simulate the attenuation effect of downstream flood hydrograph. The simulated results showed that the decrease of releasing water from Ubol Ratana and Lam Pao reservoirs by 10, 30 and 50 % during the wet year (2001), affected the decrease of peak flood by 5.86%, 17.57%, and 26.59%, respectively. In conclusion, reducing existing reservoir releases should be considered as part of proactive flood risk reduction measures, and the HECHMS model is able to describe the hydrological processes through underlying physical and mathematical relations.

Comparison of an Automated and Manual Method for Calculating Storm Runoff Response in Ungauged Catchments in Serbia

Abstract Estimation of discharge from ungauged catchments based on rainfall-runoff analysis is a very frequent task in engineering hydrology. Very often, design discharges are needed for streams or small rivers where no streamflow data is available (river training works, culverts, small hydropower plants, etc). This study uses a well established lumped hydrologic rainfall-runoff model to compare two different approaches in data preparation. The traditional method of manual obtainment of catchment parameters was compared to a more contemporary methodology using automation with geographic information systems, digital terrain models and available datasets, with an emphasis on open-source tools and freely available datasets. Both techniques were implemented on more than 100 catchments in Serbia to calculate storm runoff response. The results show minor differences that are insignificant compared to the time and resources saved with the automated techniques. The use of such automated methods enables the hydrologist to direct more attention to other factors that influence discharge even more than catchment parameters, such as rainfall, soil and land use data.

Assessment of a seasonal calibration technique using multiple objectives in rainfall–runoff analysis

AbstractThe hydrological response characteristics for the catchments in the Republic of Korea are related to a strong seasonality in the rainfall and streamflow distributions with distinct wet and dry seasons. This study aims to improve a model's ability to predict streamflows by minimizing information loss from the available data during the calibration processes. This study assesses calibration techniques incorporating a multi‐objective approach and seasonal calibration. The lumped conceptual rainfall–runoff model IHACRES was applied to selected catchments in Korea. The model was calibrated based on three different methods: the classical approach using a single performance statistic (the single‐objective method), the multi‐objective approach (the multi‐objective method (I)) and the combined approach incorporating multi‐objective and seasonal calibrations (the multi‐objective method (II)). In the multi‐objective approach, the ‘best fit’ models in the calibration period were selected by considering the trade‐offs among multiple statistics. During seasonal calibration, the calibration period was divided into four seasons to investigate whether these calibrated models can improve the model performance with regards to seasonal climate, rainfall and streamflow distributions. The adequacy of the three different calibration methods was assessed through comparison of the variability of model performance in high and low flows and water balance for the entire period and for each seasonal period. The multi‐objective methods yielded more accurate and consistent predictions for high and low flows and water balance simultaneously, compared to the single‐objective method. In particular, the multi‐objective method (II) produces the best modelling capacity to capture the non‐stationary nature of the hydrological response under different climate conditions. The pattern of improvement with the multi‐objective method (II) was generally consistent through the seasons, with the exception of the winter period in the regions partially affected by snow. This exception is due to a potential limitation of the IHACRES model in reflecting the impact of snow on the catchment hydrology. Copyright © 2013 John Wiley & Sons, Ltd.

森林の土壌保水力を考慮した高精度な流出解析手法を用いた林相変化に関する降雨流出解析

森林の土壌保水力を考慮した高精度な流出解析手法を用いた林相変化に関する降雨流出解析

Effective Flood Control Through Integrated and Collaborative Dam Operation at Three Dams in the Upper Nabari River

Heavy rain with Typhoon 18 threatened the Nabari River Basin, Kansai region, with inundation early on the morning of October 8, 2009. The Nabari River is a tributary of the Yodo river basin that contains Osaka and Kyoto and runs through Nabari City, which is a residential zone a commutable distance from Osaka city. In the upper reaches of the Nabari, there are three multipurpose dams – Shorenji Dam, Hinachi Dam, and Murou Dam – that are operated by the Kizugawa Integrated Dam Control and Management Office (KIDCMO), a branch office of the Japan Water Agency (JWA). Since it rained heavily downstream from the three dams, regular operation of the dams complying with given flood control regulations appeared unable to save Nabari City from inundation. The JWA and Ministry of Land, Infrastructure, Transport and Tourism (MLIT) therefore conducted collaborative operation of the three dams to avoid inundating the city. In this case, flood control operation of the three dams commenced at an early stage before inflow reached defined flood discharge in consideration of the water level of the Nabari River, rainfall conditions, and the capacity of reservoirs. During operation, discharge from dams was changed in a timely manner and appropriately through collaborative operation of the three dams in order to maximize the effectiveness of all flood control capacities of reservoirs based on the latest rainfall forecast technology and runoff analysis. The use of improved rainfall forecast technology and runoff analysis models enabled effective application of flexible operation protocols. It is estimated that this operation has resulted in a 1.5 m decrease in the water level at the Nabari design control point and saved approximately 1,200 households from inundation. Considering recent climate change, it is possible to have extreme rainfall more often. The proof of the adaptability of this flexible operation is quite meaningful not only for flood damage mitigation in the downstream but also for future prospects of flood control by dams.

Study of overland flow phenomenon using experimental and modelling approaches

Rainfall-runoff analysis of a watershed is needed for the purposes of water resources planning, design flood estimation, flood forecasting, study of movement of pollutants, and many other applications. For a mathematical simulation of this phenomenon, controlled rainfall-runoff experimental runs were conducted on the V-catchment system placed over the advanced hydrologic system to obtain runoff hydrograph data. The approximate convection–diffusion (ACD) equation–based overland flow model was used for simulation of these observed hydrographs. Considering various combinations of runoff simulation scenarios, a total of 111 laboratory experiments were conducted on two types of overland flow and channel flow roughness conditions generated (1) on a V-catchment model made up of acrylic sheet surface and (2) with artificial roughness surface generated with the help of sand paper pasted on the acrylic V-catchment model. These 111 experimental runs were made corresponding to six rainfall intensity inputs, that is, varying from 54 to 84 mm/hour, and for four overland plane slope conditions varying from 0.22% to 1.54%, for each of the three channel slopes used. Overall, it is demonstrated that the ACD equation–based overland flow model is able to reproduce the observed hydrographs closely, in many cases with Nash–Sutcliffe efficiency greater than 90%. But in all the experiments, the recession limb of the observed hydrographs could not be reproduced very closely because of prolonged flow of water. The reason behind this behaviour could be attributed to the retention of runoff of the recession limb because of surface water tension prevailing over the overland flow bed, channel bed and even over the weir model used for flow measurement. Except for this problem, the experimental set-up established in the laboratory reasonably generates overland flow hydrographs which could be reproduced by the overland flow model developed based on the ACD equation, including those cases of diffusion behaviour of the V-catchment experimental hydrographs.

침수피해 저감을 위한 지하저류조 설치에 관한 연구

도시지역에서의 내수침수에 의한 침수피해는 우수에 대한 배수시설물의 시설용량 부족, 대상지구내 저류지, 유수지 및 조정지의 부족, 배수펌프장 용량부족 등에 의한 범람으로 야기된다. 침수면적은 일반적으로 소규모이지만 도시지역의 경우 자산밀집도가 높아 단위면적당 피해밀도가 높다. 따라서 집중호우에 따른 내수배제의 불량을 고려한 침수구역의 정확한 추정이 필요하며, 이를 통하여 대비책을 강구하는 것이 중요하다. 본 연구에서는 대구광역시 서구 비산7동 지역을 배수구역으로 선정하여 집중호우발생시 유출특성을 모의하고, 침수피해를 저감시키기 위한 방안으로 지하저류조의 설치에 따른 침수피해 저감효과에 대한 분석을 실시하였다. 국지적인 돌발홍수 및 이상호우에 대한 기존 시설물의 배제능력을 검토하고 지하저류조의 설치에 따른 침수피해 저감효과를 분석하기 위하여 10년, 20년, 50년 및 100년 빈도의 확률강우에 대한 유출해석을 실시하였고, 유출해석을 통하여 계산된 월류량에 대한 2차원 침수해석을 실시하여 최대 침수심 및 최대 침수면적을 계산하였다. 본 연구에서는 최대 월류량이 발생하였던 100년 빈도, 지속시간 180분의 확률강우에 대하여 지하저류조 설치에 따른 유출해석을 수행하여 월류량 발생을 저감시킬 수 있는 최적의 지하저류조 위치 및 규모를 분석하였다. The flood damage in urban area has been caused by lack of capacity of drainage facility, insufficient water retention, reservoir & regulation pond, and lack of capacity for drainage pump station etc. In general, inundation area used to be in small scale but in case of urban area, due to high density of assets, it has been experiencing high density of damage in terms of per unit area. Thus it is necessary to have accurate estimation of inundation area by taking into account poor drainage system in connection with heavy rainfall. In this study, runoff simulation during heavy rainfall was carried out in the area of Bisan drainage basin and the effect of reduction of inundation by the installation of underground storage facilities was analyzed as a method to reduce the damage of inundation. To examine existing drainage capacity in time of flash flood as well as abnormal heavy rainfall and to analyze mitigation effect of inundation damage upon installation of underground storage facilities, the rainfall runoff analysis was carried out on the probable rainfall of 10, 20, 50 and 100 year frequency which exceed facility design frequency.

토양수분과정을 고려한 GR4J 모형의 개량 및 국내유역 적용성 평가

토양수분과정은 강우사상 발생 시 유역의 반응을 결정할 때 중요하게 고려되어야 할 과정으로 저류형 수문모형에 있어서 초기 유출량을 결정하는 역할을 한다. 이 같은 토양수분과정은 연속형 NRCS 방법에 주로 사용되었으나 초기강우손실 가정의 문제점 때문에 강우발생사상에 대하여 일부 사상은 설명할 수 없다. 본 연구에서는 NRCS 방법의 초기강우손실 가정의 문제점을 해결하고자 수정된 토양수분과정을 고려하여 모형을 개량하고 개량한 모형을 국내유역에 적용하여 적용성을 평가하였다. 수정된 토양수분과정 개선절차 적용에 있어서 집중형 장기강우유출모형인 GR4J(Ge'nie Rural a 4 parame tres Journalier)를 선택하여 개선하였다. 이를 기존의 결과와 비교하여 개선된 절차가 결과에 어떤 영향을 미치는 지 살펴보았다. 이 과정에서 모형의 매개변수 추정은 최적화 알고리즘인 화음탐색법을 사용하였으며 매개변수 검증을 수행하여 각 매개변수가 유역의 특성을 대표하는지 확인하였다. 토양수분과정 개선을 통해 더 향상된 강우-유출 값을 획득하였으며 연구 결과를 토대로 토양수분과정 개선을 통해 강우-유출 과정의 정확성을 향상시킬 수 있음을 확인하였다. 유출기준저류고에 따른 토양수분과정 세분화는 유출량 추정의 정확성을 높이는 데 매우 중요한 역할을 하며 본 연구에서 사용한 GR4J 모형은 비교적 적은 매개변수를 사용하여 우수한 성능을 나타내기에 본 연구결과를 바탕으로 국내유역에서 적용하기에 적합한 모형으로 기대된다. Soil Moisture Accounting(SMA) process is an important topic in rainfall-runoff analysis because it determines the initial discharge in hydrological models. The SMA process is used in continuous NRCS method. However, it can not explain some events due to its assumption of initial rainfall losses. In this study, a modified SMA procedure is applied to solve the problem with the initial rainfall losses assumption of the NRCS method, and a modified GR4J model is developed using the modified SMA procedure. To verify the applicability of the proposed model, the results are compared with those from existing GR4J models in three different Korean basins. In this process, Harmony Search optimization algorithm is used to calibrate model parameters. And the calibrated parameters are verified to check the representability of the target basin. The developed model shows better results than existing models do and can improve accuracy of the rainfall-runoff model. Since the modified GR4J model shows outstanding efficiency while using less parameters, it is expected to be applied to many other Korean basins.

대도시 복합유역의 지표 및 지표하 유출해석기법 개발 (II) - 분석 및 적용 -

In this study (II), the module developed in the previous study (I) has been tested on application and numerical stability. The runoff module was compared the result of analysis with two different models (FFC2Q and ) considering characteristic of infiltration. To examine the application and stability of developed module, runoff aspect was simulated under the variety case of rainfall intensity, effective soil depth, elapsed time. The development module was presented typical type of infiltration process looking physically, the different of saturation point on soil type, and characteristic of soil type. Also, the module was reflected in the runoff feature about rainfall intensity and time distribution. Finally, this paper drew a conclusion that result of rainfall-runoff analysis as compared with difference models (FFC2Q and ) has a high accuracy.

자연하안조성을 위한 SWAT-K 모의치 기반 유황 분석

In this study, the method of estimating hydrologic information (water depth, submerged period etc.) on the proper selection of construction point and scale as well as vegetation type suggested for the design of natural riparian rehabilitation structure. Long-term comprehensive watershed model SWAT-K(Korea) was applied to this purpose. Flow duration analysis was conducted to analyze the hydrologic characteristics of Pyungchang watershed at which the 'bangtul' construction method was tested. For this purpose 20 years (1989-2008) rainfall runoff analysis was carried out. Based on the simulated daily streamflow data, flow duration curve was made to analyze the flow characteristics, and the water depth hydrograph was made to analyze the water depth distribution at the cross section. Finally, the information for the selection of proper vegetation according to the submerged period is suggested.

고해상도 위성영상을 이용한 도시유역의 소강우 유출해석

Abstract : In this research, enhanced land-cover classification methods using high-resolution satellite image (HRSI) and GIS in terms of practicality and accuracy was proposed. It aims for understanding non-point pollutant origin/loading, assessment the efficiency of rainfall storage/infiltration facilities and sounds water-environment management. The result of applying enhanced land-cover classification methods to the urban region verifies that roof and road area are including various vegetations such as roof garden, flower bed in the median strip and street tree. This accounts for 3% of total study area, and more importantly it was counted as impervious area by GIS alone or conventional indoor work. The feasibility of the method was assessed by applying to rainfall-runoff analysis for three weak rainfall in the range of 7.1-10.5 mm events in 2000, Chiba, Japan. A good agreement between simulated and observed runoff hydrograph was obtained. In comparison, the hydrograph simulated with land-use parameters by the detailed land-use information of 10m grid had an error between 31%~71%, while enhanced method showed 4% to 29%, and showed the improvement particularly for reproducing observed peak and recession flow rate of hydrograph in weak rainfall condition.

Sampling error of areal average rainfall due to radar partial coverage

Areal average rainfall is important as it is used as an input for most rainfall-runoff analysis in Hydrology and Water Resources. Different from traditional methods of using rain gauge data, the use of radar rainfall for the estimation of areal average rainfall is very straightforward. However, in some cases with severe terrain blockages, the value of the incomplete radar information is of serious concern. This study investigated this problem and derived an equation for estimating the error involved in the areal average rainfall due to partial radar coverage of a basin or sub-basin. When only partial radar information is available, the sampling error decreases with increasing radar coverage and the number of radar bin clusters. As an application example, this study considered the Han River Basin with its rainfall observations using the Ganghwa rain radar. Among a total of 24 mid-sized sub-basins in the Han River Basin evaluated, only five sub-basins were fully covered by the radar and three were totally uncovered. The remaining 16 sub-basins were covered partially by radar leading to incomplete radar information. The results show that the sampling error ranged from several % to tens % of standard deviation of the areal average rainfall depending on the relative areal radar coverage.

Long Term Distributed Rainfall Runoff Analysis and Its Application to River Planning

Long Term Distributed Rainfall Runoff Analysis and Its Application to River Planning

Real-time flood forecasting of the Tiber river in Rome

The aim of present work is to investigate the real applicability of real time model of flood forecasting in Tiber river in Rome in order to assess if the lead time is compatible with civil protection actions.Three different models were applied: a simple regression model based on the results obtained by means of a Monte Carlo analysis; a linear model; a quasi-physically based model performing rainfall-runoff analysis. These models were applied to forecast historical floods.It is confirmed that the regression and the linear regression models seem more appropriate for flood forecasting in Rome. Finally, by applying the regression model, the optimal threshold discharges for warnings systems are identified by means of a Bayesian decisional model.