Clark Instantaneous Unit Hydrograph Research Articles

Applicability of geomorphological approaches combined with the modified Clark’s model for flood hydrograph estimation

Among the techniques available for modeling direct surface runoff (DSR), the Unit Hydrograph and the Instantaneous Unit Hydrograph (IUH) have been widely used. Clark's IUH (CIUH) stands out, mainly in its distributed version known as ModClark, which has two parameters: time of concentration (tc) and storage coefficient (R). The best procedure is to determine tc and R from observed rainfall-runoff datasets, however, they usually are not available due to a lack of monitoring or insufficient temporal discretization. Thus, geomorphological approaches have been developed to allow the estimation of tc and R from relief information of the watershed, however, their use is little disseminated in literature. In addition, only a few studies have evaluated the influence of spatial discretization of the watershed on the definition of tc and R (parameterization) and its impact on the application of geomorphological approaches for the ModClark. This work aimed to evaluate the ModClark performance for estimating DSR hydrographs in two Brazilians watersheds (Cadeia river watershed and Jaguara creek watershed), using four little-known geomorphological approaches (PST, POA, PD, and PMC) for the determination of its parameters under two parameterization schemes: lumped and semi-distributed. The following findings were evidenced: i) the application of the ModClark presented a satisfactory performance for estimating DSR hydrographs; ii) the characteristics of the selected rainfall-runoff events also had a significant influence on the estimation of the DSR hydrographs; iii) the lumped parameterization scheme provided more adequate parameters for ModClark, thus resulting in more accurate DSR hydrographs; iv) PST gave the most accurate estimated DSR hydrographs for the Cadeia river watershed under both schemes and for the Jaguara creek watershed under the lumped scheme, whereas PMC outperformed the other approaches for Jaguara creek watershed under semi-distributed; and v) for watersheds with geomorphological characteristics similar to those of the watersheds analyzed in this study, PST would be the most suitable geomorphological approach for determining the ModClark’s parameters.

Hillslope Contribution to the Clark Instantaneous Unit Hydrograph: Application to the Seolmacheon Basin, Korea

In this study, the time–area curve of an ellipse is analytically derived by considering flow velocities within both channel and hillslope. The Clark IUH is also derived analytically by solving the continuity equation with the input of the derived time–area curve to the linear reservoir. The derived Clark IUH is then evaluated by application to the Seolmacheon basin, a small mountainous basin in Korea. The findings in this study are summarized as follows. (1) The time–area curve of a basin can more realistically be derived by considering both the channel and hillslope velocities. The role of the hillslope velocity can also be easily confirmed by analyzing the derived time–area curve. (2) The analytically derived Clark IUH shows the relative roles of the hillslope velocity and the storage coefficient. Under the condition that the channel velocity remains unchanged, the hillslope velocity controls the runoff peak flow and the concentration time. On the other hand, the effect of the storage coefficient can be found in the runoff peak flow and peak time, as well as in the falling limb of the runoff hydrograph. These findings are also confirmed in the analysis of rainfall–runoff events of the Seolmacheon basin. (3) The effect of the hillslope velocity varies considerably depending on the rainfall events, which is also found to be mostly dependent upon the maximum rainfall intensity.

Sensitivity analysis of relationships between hydrograph components and landscapes metrics extracted from digital elevation models with different spatial resolutions

Evaluation of sensitivity of hydrograph components and landscape metrics extracted from various spatial resolutions reveals relationships between landscape metrics and outflow properties with the lowest error. In the present study, 14 Digital Elevation Models (DEMs) with different resolutions derived from a vector and raster-radar source were analyzed to evaluate sensitivity of relationships between simulated hydrograph components and landscape metrics using multiple regression methods in the Galazchai Watershed, West Azerbaijan Province, Iran. To this end, DEM, slope, flow length and direction and time of concentration were developed in the vector and raster scales of 1:25000 and Advanced Land Observing Satellite-1 (ALOS) with different resolutions using ArcGIS 10.5 and ArcHydro software. Accordingly, 588 Direct Runoff Hydrographs (DRHs) were produced and clustered using Clark's Instantaneous Unit Hydrograph (IUH) model. The results showed that the best regression fits for flood volume and peak discharge were determined with Number of Disjunct Core Areas (NDCA) and Patch Density (PD) landscape metrics. Furthermore, the best regression fitted for time to peak and base time were observed with Core Area (CA) and Normalized Landscape Shape Index (NLSI) landscape metrics. In addition, the sensitivity analysis shows that the most sensitive spatial resolutions in modeling relationship between flood volume and peak discharge were determined at 5, 10, 20, and 30 m. The results revealed that hydrograph components in association with landscape metrics had high sensitivity to spatial resolutions, while the relationships between hydrological components and landscape metrics without considering the optimal spatial resolutions resulted in unacceptable results.

Changeability of simulated watershed hydrographs from different vector scales and cell sizes

The effects of various vector scales (125000–1:250000) and cell sizes (5–200 m) on the modeling performance of hydrographs was evaluated using the time-area histograms (TAHs) based on Clark's Instantaneous Unit Hydrograph (IUH) model for the Galazchai watershed, Iran with an area of 103 km2. Some 960 direct runoff hydrographs (DRHs) were produced and clustered based on Relative Errors (REs) for hydrograph components, Coefficient of Efficiency (CE) and Root Mean Squared Errors (RMSEs). Results showed that the vector scales of 1:25000 with cell sizes of 30 and 100 m, and also 1:25000 with cell sizes of 20 and 200 m were the critical vector scales and cell sizes from the viewpoint of CEs and RMSEs, respectively. In addition, the mean relative errors resulting from flood volume, peak discharge, time to peak, and base time were estimated to be – 3.06, + 8, − 4.51 and + 5.42% for the critical scales and cell sizes as a result of clustered simulated hydrographs. The mean values of CE and RMSE were also estimated as 73 and 2%, respectively.

Effect of Time-Area Percent Curves in Development of Clark Model Unit Hydrograph

This paper describes the effect of time – area percent curves in the development of Clark model unit hydrograph. This hydrology modelling study refers to event base modeling in order to derive the unit hydrograph from Clark instantaneous unit hydrograph. For this study, Kelani river basin up to Hanwella gauging site has been represented as the study area. Hydrologic Modelling System software developed by HEC, USA (HEC-HMS) has been used for the development of unit hydrographs under the Clark UH transform model. Three numbers of different time – area percent curves of Kelani river basin have been asynchronously used as input to the Clark UH transform model in order to obtain different simulations. The parameters, time of concentration Tc and storage coefficient R values were calibrated and validated individually, against the various percent curves for the future analysis. The best suitable percent curve is identified based on the goodness of fit criteria, Nash-Sutcliffe Efficiency (NSE) with high accuracy. For the Loss model, initial and constant rate method was preferred. In the Meteorological Model, Gaged weight was considered for rainfall analysis. For the Transform Model or Direct Runoff Model, Clark UH is considered. For the Base flow model Recession, constant option was preferred. The Calibration (manual and automatic) was conducted for the storm events of May 2017, December 2014 and November 2012.Validation was conducted for the storm event of June 2014. The calibration and validation process was conducted for analyzing the hourly rainfall-runoff data for storm events observed during the monsoon seasons of the relevant years. The conclusions of the study would be very much applicable for the key personnel for taking structural and non-structural measures against the flood menace which is a frequent challenge over the study area concerned.

Accuracy of sedimentgraph modeling from topography map scale and DEM mesh size

The evaluation of scale effects on modeling performance of sedimentgraphs as the ultimate outputs of the hydrological simulation is vital for adaptive watershed management. The present study therefore analyzed effectability of simulated sedimentgraphs components in association with different topographic maps with various vector scales. The whole procedure was materialized to select the critical scale and cell size for the Galazchai Watershed, Iran. To this end, the stormwise sedimentgraphs were modeled for 23 recorded events using the Clark's Instantaneous Unit Hydrograph (IUH) model stemmed for developing Instantaneous Unit Sedimentgraphs (IUSGs) incorporated with dimensionless sediment concentration distribution (DSCD) based on the vector scales of 1:25000, 1:50000, 1:100000 and 1:250000 and cell sizes of 5, 10, 20 30, 50, 100 and 200 m. Some 644 direct sedimentgraphs (DSGs) were then evaluated based on Relative Errors (REs) for sediment volume, peak sediment, time to peak, base time and the Coefficient of Efficiency (CE). The results confirmed that REs for peak sediment, time to peak and CE were sensitive to cell size. The results further verified that the cell sizes of 5, 20, 30, 50 and 100 m were critical cell sizes in viewpoint of time to peak. In addition, the vector scales of 1:50000 with cell size of 50 m, and 1:100000 with cell sizes of 5 and 10 m were critical vector scales and cell sizes based on RMSE evaluation criterion. It is concluded from the current research that the accuracy of simulation of sedimentgraph was influenced by map scales and mesh sizes.

The importance of the objective functions and flexibility on calibration of parameters of clark instantaneous unit hydrograph

The paper compares the results of automatic calibration of Clark’s synthetic unit hydrographs. Optimal values of model parameters were determined by the objective functions: percentage error in peak flow (PEPF), percentage error in volume (PEV), peak-weighted root mean square error (PWRMSE), sum of absolute residuals (SAR) and sum of squared residuals (SSR). The last part of the analysis assesses the flexibility of studied model. The research was performed in the upland watershed of Grabinka – left tributary of the Wisloka river located in Southern Poland. The analysis reveals that the smallest differences between the maximum flow in the observed and calculated flood culmination were obtained when applying PWRMSE function. This paper also indicates, that Clark’s model was efficient for describing the analyzed floods.

Application of HEC-HMS programme for the reconstruction of a flood event in an uncontrolled basin / Zastosowanie programu HEC-HMS do odtworzenia wezbrania powodziowego w zlewni niekontrolowanej

Abstract The paper presents an assessment of the applicability of HEC-HMS programme to simulate a precipitation flood event in an ungauged basin. The programme has been developed by the Department of the Army Corps of Engineers and enables conducting hydrological calculations for basins with different characteristics and including a number of meteorological factors. The application of this model in Polish conditions was verified in the basin of the Stobnica River - a right tributary of the Wisłok River. The calculations were carried out for the flood event caused by a continuous rain, which occurred in April 1998. Four hydrological models were compared: geomorpho-climatic instantaneous unit hydrograph by Nash - GcIUH_Nash, Snyder's synthetic unit hydrograph with the determination of parameters by regression models - Snyder_reg and standard method - Snyder_ stand and Clark's instantaneous unit hydrograph - IUH_Clark, where the model parameters were optimized in the programme. The calculations revealed that the best simulation results were obtained with the Snyder_stand and Snyder_reg models. Further research should be directed to verifying the applicability of HEC- -HMS programme for hydrological analyses of much more extensive hydrometric material and basins with different characteristics.

Uncertainty of areal average rainfall and its effect on runoff simulation: A case study for the Chungju Dam Basin, Korea

This study investigated the relationship between the errors involved in the areal average rainfall estimation and the runoff simulation (hereafter, rainfall and runoff errors). The error statistics of the observed areal average rainfall were estimated and used for the generation of input data for the runoff simulation. The Clark instantaneous unit hydrograph was used for this runoff simulation. The runoff model parameters were estimated using several sets of rainfall-runoff data observed, whose statistics were then used for the sensitive analysis of the model simulation on the parameter sets. The rainfall error in this study was defined as the relative difference between the observed and generated areal average rainfall. On the other hand, the runoff error was designed to consider the runoff volume, peak flow and peak time, respectively. This study was applied to the Chugnju Dam Basin, Korea. The results obtained are as follows: (1) The variation of model parameters estimated in this study were about 30% of their means. Also, the effect of this error in model parameter estimation on runoff simulation was found to be maximum 15% of the peak flow. (2) The estimation error of areal average rainfall was found roughly proportional to the areal average rainfall itself. Both the rainfall and runoff errors were found to have no obvious biases. However, the variance of the peak flow error was found to be significantly higher. (3) The relationship between rainfall error and runoff volume error was roughly one to one, however, the rainfall error has become amplified by more than 50 % and transferred to the peak flow error.

A practical estimation of Clark IUH parameters using root selection and linear programming

AbstractThe values of the parameters of the Clark instantaneous unit hydrograph (IUH) are often relying on the subjective decision of the researcher, which leads to large variations of their values. Therefore, an objective method minimizing the subjective judgement in the IUH modelling procedure while providing a reduced range of acceptable values is proposed. The proposed method uses a basin average IUH to mitigate the robustness problem of the Clark IUH parameters. Using linear system theory, the z‐transform is applied to the average IUH and then the IUH polynomial is factored into the recession and time‐area curve (TAC) components based on a convolution relation between the Clark IUH parameters. During this calculation, the root selection method was adopted to verify the storage coefficient R from the recession component and a linear programming technique was applied for determining the TAC for the basin of interest. The Wi River basin was used to test the applicability of the proposed method. The results showed that the components of a single reservoir and the TAC for Clark IUH were separated effectively, and acceptable values for the parameters were obtained. Copyright © 2011 John Wiley & Sons, Ltd.

COMPARISON BETWEEN CHARACTERISTICS OF GEOMORPHOCLIMATIC INSTANTANEOUS UNIT HYDROGRAPH BE PRODUCED BY GcIUH BASED CLARK MODEL AND CLARK IUH MODEL

A great number of developing countries do not have sufficient rainfall-rainoff data of watersheds. For designing a hydraullic structure, considering the basic characteristics of synthetic unit hydrograph is quite indispensable. The geomorphoclimatic approach considers the rainfall and the properties of the watershed. This method can provide a better representation of the runoff estimation. In this study, a geomorphoclimatic instantaneous unit hydrograph (GcIUH) model has been developed. It's derived from the parameters of the CLARK instantaneous unit hydrograph (IUH) which completes its shape. GcIUH based Clark model was applied from the Kasilian watershed in northern part of Iran, The Direct Surface Run Off (DSRO) hydrographs are estimated by the GcIUN based Clark model. Its DSRO hydrographs have been compared with the DSRO hydrographs computed by the Clark IUH model option of the HEC-HMS package. On the basis of quantitative evaluation of the model, it was found that the model is applicable for predicting storm surface runoff in the study area.

COMPARISON BETWEEN CHARACTERISTICS OF GEOMORPHOCLIMATIC INSTANTANEOUS UNIT HYDROGRAPH BE PRODUCED BY GcIUH BASED CLARK MODEL AND CLARK IUH MODEL

A great number of developing countries do not have sufficient rainfall-rainoff data of watersheds. For designing a hydraullic structure, considering the basic characteristics of synthetic unit hydrograph is quite indispensable. The geomorphoclimatic approach considers the rainfall and the properties of the watershed. This method can provide a better representation of the runoff estimation. In this study, a geomorphoclimatic instantaneous unit hydrograph (GcIUH) model has been developed. It's derived from the parameters of the CLARK instantaneous unit hydrograph (IUH) which completes its shape. GcIUH based Clark model was applied from the Kasilian watershed in northern part of Iran, The Direct Surface Run Off (DSRO) hydrographs are estimated by the GcIUN based Clark model. Its DSRO hydrographs have been compared with the DSRO hydrographs computed by the Clark IUH model option of the HEC-HMS package. On the basis of quantitative evaluation of the model, it was found that the model is applicable for predicting storm surface runoff in the study area.

Application of a regionalized Clark IUH model with limited hydrologic data availability

AbstractTo aid prediction of the flow hydrograph in a basin with limited data, a practical approach to determining a regionalized Clark instantaneous unit hydrograph (IUH) model is presented. The proposed model is described in terms of the synthetic time–area concentration curve, the concentration time, and a special regional similarity value that is valid in the whole basin. The latter was estimated from a Monte Carlo testing procedure based on the normal probability distribution of transformed regional similarity values composed of the time of concentration and the storage coefficient in gauged basins. The time–area concentration curve and the concentration time were calculated from a rational equation as in conventional methods. The method of transformation adopted was the Box–Cox power transformation, which is known to make non‐normal values resemble normal data. By introducing the regional similarity value into a Clark IUH, a statistically best estimate of IUH for given data conditions and its quantified degree of uncertainty were realized. The Wi River basin in Korea was used to test the applicability of the regionalized Clark IUH. The performance of the suggested methodology was evaluated by assuming an ungauged sub‐basin at the site. The results showed that the IUH model developed in this work was an effective tool, predicting a reliable hydrograph within the study area even though only limited data were available. Copyright © 2008 John Wiley & Sons, Ltd.

Runoff estimation for an ungauged catchment using geomorphological instantaneous unit hydrograph (GIUH) models

AbstractA geomorphological instantaneous unit hydrograph (GIUH) is derived from the geomorphological characteristics of a catchment and it is related to the parameters of the Clark instantaneous unit hydrograph (IUH) model as well as the Nash IUH model for deriving its complete shape. The developed GIUH based Clark and Nash models are applied for simulation of the direct surface run‐off (DSRO) hydrographs for ten rainfall‐runoff events of the Ajay catchment up to the Sarath gauging site of eastern India. The geomorphological characteristics of the Ajay catchment are evaluated using the GIS package, Integrated Land and Water Information System (ILWIS). The performances of the GIUH based Clark and Nash models in simulating the DSRO hydrographs are compared with the Clark IUH model option of HEC‐1 package and the Nash IUH model, using some commonly used objective functions. The DSRO hydrographs are computed with reasonable accuracy by the GIUH based Clark and Nash models, which simulate the DSRO hydrographs of the catchment considering it to be ungauged. Inter comparison of the performances of the GIUH based Clark and Nash models shows that the DSRO hydrographs are estimated with comparable accuracy by both the models. Copyright © 2007 John Wiley & Sons, Ltd.

GIUH based Clark and Nash models for runoff estimation for an ungauged basin and their uncertainty analysis

Runoff estimation is an important aspect of river basin planning, development and management. Geomorphological instantaneous unit hydrograph (GIUH) approach holds a great potential for estimation of runoff from ungauged basins because of its direct application to ungauged basins, without going for cumbersome procedure of regionalization. In this study, GIUH is derived from the geomorphological characteristics of a basin and it is related to the parameters of the Clark instantaneous unit hydrograph (IUH) model as well as Nash IUH model for deriving its complete shape. The developed GIUH based Clark and Nash models are applied for simulation of the direct surface runoff (DSRO) hydrographs for ten rainfall‐runoff events of the Ajay basin upto Sarath gauging site of eastern India. The geomorphological characteristics of the Ajay basin are evaluated using the GIS package, Integrated Land and Water Information System (ILWIS). A comparison of the performances of the GIUH based Clark and Nash models in simulating the DSRO hydrographs by employing some of the commonly used error functions reveals that the DSRO hydrographs are computed with reasonable accuracy by both the models, which simulate the DSRO hydrographs of the basin considering it to be ungauged. The relative sensitivity and the degree of uncertainty associated with each of the input parameters of the GIUH based Clark and Nash models have been quantified. The uncertainty analysis reveals that apart from the velocity (V) parameter, the length of the highest order stream (LO) is the only geomorphological parameter which results in higher degree of uncertainty in derivation of unit hydrograph using the GIUH based Clark and Nash models, and hence, it is to be evaluated with greater precision for accurate runoff estimation from ungauged basins.

PROJECTION OF URBANIZATION EFFECTS ON RUNOFF USING CLARK INSTANTANEOUS UNIT HYDROGRAPH PARAMETERS1

ABSTRACT: To alleviate serious flooding problems brought upon by rapid urbanization in the Beargrass Creek watershed, located in Louisville, Kentucky, the U.S. Army Corps of Engineers undertook a major flood study in 1973. In order to predict flood conditions in 1990, the year when the watershed was expected to undergo complete urbanization, trends in the Clark Instantaneous Unit Hydrograph (Clark IUH) parameters were utilized to determine the 1990 unit hydrograph and flood conditions. Based on the results from this flood study, this paper demonstrates the applicability of using projected Clark IUH parameters for modeling future runoff conditions in an urbanizing watershed. Values of these parameters, as estimated from maximum annual historical flood data, are used to develop regression models for predicting future Clark IUH parameters. Using the projected parameters, selected annual flood events since 1973 are simulated in order to verify the accuracy of these projections. Results show a close correspondence between the simulated and observed flood characteristics. Hence, the use of projected Clark IUH parameters is an appropriate procedure for modeling future runoff conditions in an urbanizing watershed.