Synopsis When a distributed hydrological model is used for real-time flood prediction, how to upd... more Synopsis When a distributed hydrological model is used for real-time flood prediction, how to update the spatially distributed state variables is an important issue to obtain accurate prediction. This study introduces three methods to update the state variables in a distributed hydrological model during a simulation. The introduced methods here, two kinds of ratio method, consider a spatial distribution of hydrologic variables in a basin. With the ratio method, state variables are updated successfully and better simulation results can be obtained than when the variables are not updated.
Synopsis This study proposes a physically-based distributed instantaneous unit hydrograph by adop... more Synopsis This study proposes a physically-based distributed instantaneous unit hydrograph by adopting the concept of IUH, which is derived based on physical runoff mechanism by combining DEM s, remote sensing and kinematic wave approximation. The heterogeneity of the watershed can be well represented by DEMs, remotely sensed data and kinematic wave approximation in the proposed physically-based distributed instantaneous unit hydrograph. As for ungauged area or the area with poor hydrologic record, the geomorphologic IUH proposed in the study is expected to be a reference for water resources designing and evaluation.
The most realistic and widely used approach to estimate the hydrological impacts of climate chang... more The most realistic and widely used approach to estimate the hydrological impacts of climate change is to combine the output of the GCMs with a hydrological model that contains physically-based mathematical descriptions of hydrologic phenomena. This study sets out to investigate the possible impacts of climate change in a hydrological view point including water resources and flood producing mechanisms on two main river basins of Japan, Tone River and Yodo River basins. The output of very high resolution atmospheric model is analyzed, and the runoff simulation results with the hydrologic model are described.
A natural rainfall-runoff process is conceptualized (or modeled) by hydrologist’s perception or e... more A natural rainfall-runoff process is conceptualized (or modeled) by hydrologist’s perception or experience in mathematical form. These rainfall-runoff models are usually calibrated and verified based on streamflow data at the outlet of interest. The streamflow data, aggregated response over a catchment is obviously required but is not sufficient information to identify conceptual parameters of such models since numerous parameter combinations can often result in either identical model performance measures or indistinguishable hydrographs. One of the efficient techniques to enhance the parameter identification is to use additional constraints (or complementary information) in model calibration. This study aims to exemplify the equifinality problem due to insufficiency of model identification based only on streamflow data in distributed rainfall-runoff modeling. Moreover, a potential use of additional constraints provided by a computational tracer method is presented in order to rejec...
칼만필터 알고리즘을 분포형 유출모형에 적용하였다 관측 유량과 상태변수인 유역내 저류량을 갱신하고 . 자 를 도입하였고 갱신된 저류량과 모형에 의해 모의된 저류량의 비율을 유역... more 칼만필터 알고리즘을 분포형 유출모형에 적용하였다 관측 유량과 상태변수인 유역내 저류량을 갱신하고 . 자 를 도입하였고 갱신된 저류량과 모형에 의해 모의된 저류량의 비율을 유역 내 각 지점의 수위 Q-S curve , 에 적용하므로써 분포화 된 상태변수를 효율적으로 갱신하였다 갱신된 상태변수와 상태변수 오차의 시간갱 . 신은 몬테 카를로 시뮬레이션을 이용하여 모의하였다.
Hydrologic frequency analysis provides basic information for the planning, design, and management... more Hydrologic frequency analysis provides basic information for the planning, design, and management of hydraulic and water resources systems for promoting the river basin quality and human health. It uses meteorological/hydrological extreme-value data and probability distribution functions to estimate T-year events (quantiles). Reviewing the history of hydrologic frequency analysis in Japan, this study describes goodness-of-fit criteria such as the standard least-squares criterion and Akaike information criterion and their applications. The jackknife and bootstrap methods are introduced as useful resampling methods for bias correction and quantile variability estimation. As future directions, this study proposes the incorporation of (1) partial duration series or peaks-over-threshold series, if available, instead of the annual maximum series; (2) a nonparametric method using empirical distributions for larger samples with more than 100-year observation period; and (3) probable maximum...
Many hydrological and meteorological applications require knowledge about spatial and temporal va... more Many hydrological and meteorological applications require knowledge about spatial and temporal variabilities of rainfall over an area. The intensity of point precipitation is only applicable for relatively small areas. For larger areas, design rainfall needs to be converted to average areal depths. Areal Reduction Factors (ARFs) have been commonly used to obtain this transformation. To estimate ARFs at sparely gauged basins, to derive the IntensityDuration-Area-Frequency (IDAF), it is essential to incorporate the scaling properties of rainfall in time and space. The IDAF curves are determined for the evaluation of design rainfall using a scaling approach. The variabilities of annual maximum rainfall intensity in area and duration are represented through the scaling properties in time and space. Thus the scaling relationships of mean rainfall intensity with area and duration are derived using the concepts of scaling properties. Using Generalized Extreme Value (GEV) the authors obtain...
Estimation of extreme flood for different return period is required in design of various hydrauli... more Estimation of extreme flood for different return period is required in design of various hydraulic structures. Regional flood frequency analysis is an effective method for estimating such extreme flood. Delineation of hydrologic homogeneous regions is key step in success of regional flood frequency analysis. This study deals hydrologic regionalization of Nepalese territory. Cluster analysis, a multivariate technique, is generally used to identify objectively hydrological regions. This work addresses the difficulty of allocating suitable weight to different clustering attributes by employing NRCS runoff curve number. On superimposing monsoon rainfall pattern map over runoff curve number map, five hydrologic regions were proposed. L-moment based regional hydrologic homogeneity test led finalization of hydrological homogeneous regions.
The satellite images are expected to use for monitoring and identification of the disaster area. ... more The satellite images are expected to use for monitoring and identification of the disaster area. Subtraction of two images produces a differential image, which is useful to distinguish areas with surface condition change. In the case of identification of disaster areas the differential image is produced using images acquired before and after disaster in the area of interest. However the differential images have not been used efficiently due to some reasons. First reason is seasonal change of land surface properties between acquisition times of beforeand after-disaster images. Second reason is spatial resolution of satellite images. Although middle spatial resolution satellites such as Landsat/TM and SPOT are used to distinguish larger-scale disasters such as flooding and forest fire, identification of small-scale disasters, such as landslide and collapsed buildings by earthquake, need higher spatial resolution than 10 m. In this paper, the authors proposed the new method to identify...
In Sumatra in Indonesia, large-scale plantations of oil palm and acacia trees have caused 50 % re... more In Sumatra in Indonesia, large-scale plantations of oil palm and acacia trees have caused 50 % reduction of natural forests in the 25 years between 1985 to 2009. Both climate and land cover changes may impact on regional water cycle, which potentially leads to increase the risk of flood and drought. Therefore, hydrologic process understandings and their representations by hydrological models are important steps for achieving adequate water resources and water-related disaster management. Among various hydrological processes, rainfallrunoff processes in humid tropics, which is typically characterized by flow in a deep soil layer, have been poorly understood. This study conducts field investigations and modeling to simulate rainfall-runoff and flood inundation processes at the river basin scale in the Batanghari River basin in Sumatra, Indonesia. By reflecting such conditions in the model, it conducts a long-term hydrologic simulation with climate change projected based on MRI-AGCM (2...
Synopsis When a distributed hydrological model is used for real-time flood prediction, how to upd... more Synopsis When a distributed hydrological model is used for real-time flood prediction, how to update the spatially distributed state variables is an important issue to obtain accurate prediction. This study introduces three methods to update the state variables in a distributed hydrological model during a simulation. The introduced methods here, two kinds of ratio method, consider a spatial distribution of hydrologic variables in a basin. With the ratio method, state variables are updated successfully and better simulation results can be obtained than when the variables are not updated.
Synopsis This study proposes a physically-based distributed instantaneous unit hydrograph by adop... more Synopsis This study proposes a physically-based distributed instantaneous unit hydrograph by adopting the concept of IUH, which is derived based on physical runoff mechanism by combining DEM s, remote sensing and kinematic wave approximation. The heterogeneity of the watershed can be well represented by DEMs, remotely sensed data and kinematic wave approximation in the proposed physically-based distributed instantaneous unit hydrograph. As for ungauged area or the area with poor hydrologic record, the geomorphologic IUH proposed in the study is expected to be a reference for water resources designing and evaluation.
The most realistic and widely used approach to estimate the hydrological impacts of climate chang... more The most realistic and widely used approach to estimate the hydrological impacts of climate change is to combine the output of the GCMs with a hydrological model that contains physically-based mathematical descriptions of hydrologic phenomena. This study sets out to investigate the possible impacts of climate change in a hydrological view point including water resources and flood producing mechanisms on two main river basins of Japan, Tone River and Yodo River basins. The output of very high resolution atmospheric model is analyzed, and the runoff simulation results with the hydrologic model are described.
A natural rainfall-runoff process is conceptualized (or modeled) by hydrologist’s perception or e... more A natural rainfall-runoff process is conceptualized (or modeled) by hydrologist’s perception or experience in mathematical form. These rainfall-runoff models are usually calibrated and verified based on streamflow data at the outlet of interest. The streamflow data, aggregated response over a catchment is obviously required but is not sufficient information to identify conceptual parameters of such models since numerous parameter combinations can often result in either identical model performance measures or indistinguishable hydrographs. One of the efficient techniques to enhance the parameter identification is to use additional constraints (or complementary information) in model calibration. This study aims to exemplify the equifinality problem due to insufficiency of model identification based only on streamflow data in distributed rainfall-runoff modeling. Moreover, a potential use of additional constraints provided by a computational tracer method is presented in order to rejec...
칼만필터 알고리즘을 분포형 유출모형에 적용하였다 관측 유량과 상태변수인 유역내 저류량을 갱신하고 . 자 를 도입하였고 갱신된 저류량과 모형에 의해 모의된 저류량의 비율을 유역... more 칼만필터 알고리즘을 분포형 유출모형에 적용하였다 관측 유량과 상태변수인 유역내 저류량을 갱신하고 . 자 를 도입하였고 갱신된 저류량과 모형에 의해 모의된 저류량의 비율을 유역 내 각 지점의 수위 Q-S curve , 에 적용하므로써 분포화 된 상태변수를 효율적으로 갱신하였다 갱신된 상태변수와 상태변수 오차의 시간갱 . 신은 몬테 카를로 시뮬레이션을 이용하여 모의하였다.
Hydrologic frequency analysis provides basic information for the planning, design, and management... more Hydrologic frequency analysis provides basic information for the planning, design, and management of hydraulic and water resources systems for promoting the river basin quality and human health. It uses meteorological/hydrological extreme-value data and probability distribution functions to estimate T-year events (quantiles). Reviewing the history of hydrologic frequency analysis in Japan, this study describes goodness-of-fit criteria such as the standard least-squares criterion and Akaike information criterion and their applications. The jackknife and bootstrap methods are introduced as useful resampling methods for bias correction and quantile variability estimation. As future directions, this study proposes the incorporation of (1) partial duration series or peaks-over-threshold series, if available, instead of the annual maximum series; (2) a nonparametric method using empirical distributions for larger samples with more than 100-year observation period; and (3) probable maximum...
Many hydrological and meteorological applications require knowledge about spatial and temporal va... more Many hydrological and meteorological applications require knowledge about spatial and temporal variabilities of rainfall over an area. The intensity of point precipitation is only applicable for relatively small areas. For larger areas, design rainfall needs to be converted to average areal depths. Areal Reduction Factors (ARFs) have been commonly used to obtain this transformation. To estimate ARFs at sparely gauged basins, to derive the IntensityDuration-Area-Frequency (IDAF), it is essential to incorporate the scaling properties of rainfall in time and space. The IDAF curves are determined for the evaluation of design rainfall using a scaling approach. The variabilities of annual maximum rainfall intensity in area and duration are represented through the scaling properties in time and space. Thus the scaling relationships of mean rainfall intensity with area and duration are derived using the concepts of scaling properties. Using Generalized Extreme Value (GEV) the authors obtain...
Estimation of extreme flood for different return period is required in design of various hydrauli... more Estimation of extreme flood for different return period is required in design of various hydraulic structures. Regional flood frequency analysis is an effective method for estimating such extreme flood. Delineation of hydrologic homogeneous regions is key step in success of regional flood frequency analysis. This study deals hydrologic regionalization of Nepalese territory. Cluster analysis, a multivariate technique, is generally used to identify objectively hydrological regions. This work addresses the difficulty of allocating suitable weight to different clustering attributes by employing NRCS runoff curve number. On superimposing monsoon rainfall pattern map over runoff curve number map, five hydrologic regions were proposed. L-moment based regional hydrologic homogeneity test led finalization of hydrological homogeneous regions.
The satellite images are expected to use for monitoring and identification of the disaster area. ... more The satellite images are expected to use for monitoring and identification of the disaster area. Subtraction of two images produces a differential image, which is useful to distinguish areas with surface condition change. In the case of identification of disaster areas the differential image is produced using images acquired before and after disaster in the area of interest. However the differential images have not been used efficiently due to some reasons. First reason is seasonal change of land surface properties between acquisition times of beforeand after-disaster images. Second reason is spatial resolution of satellite images. Although middle spatial resolution satellites such as Landsat/TM and SPOT are used to distinguish larger-scale disasters such as flooding and forest fire, identification of small-scale disasters, such as landslide and collapsed buildings by earthquake, need higher spatial resolution than 10 m. In this paper, the authors proposed the new method to identify...
In Sumatra in Indonesia, large-scale plantations of oil palm and acacia trees have caused 50 % re... more In Sumatra in Indonesia, large-scale plantations of oil palm and acacia trees have caused 50 % reduction of natural forests in the 25 years between 1985 to 2009. Both climate and land cover changes may impact on regional water cycle, which potentially leads to increase the risk of flood and drought. Therefore, hydrologic process understandings and their representations by hydrological models are important steps for achieving adequate water resources and water-related disaster management. Among various hydrological processes, rainfallrunoff processes in humid tropics, which is typically characterized by flow in a deep soil layer, have been poorly understood. This study conducts field investigations and modeling to simulate rainfall-runoff and flood inundation processes at the river basin scale in the Batanghari River basin in Sumatra, Indonesia. By reflecting such conditions in the model, it conducts a long-term hydrologic simulation with climate change projected based on MRI-AGCM (2...
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