SYNTHETIC UNIT HYDROGRAPH

The Journal of The University of Duhok

The Storm Runoff Volume and its Peak are important for designing and operating dams and different hydraulic structures. Watershed Modeling System (WMS) version (8.1) and The HEC-1 v (4.1) hydrological models were used in this study to estimate the Synthetic runoff hydrograph resulting from two storm events over Solag Basin which is located in Sinjar District north of Iraq, making use of available recorded storms rainfall and Synthetic unit hydrograph technique. Direct runoff hydrographs are determined using Natural Resources Conservation Service (NRCS), Snyder Synthetic Unit Hydrograph and Clark methods. Nash model was used to compare the efficiency of the Synthetic runoff Hydrograph using both Synthetic and recorded discharge data for Solag basin which were available for two storms within water years 1991-1992. Synthetic unit hydrographs are important in flood studies and water resources management.

Water Resources Management, 2007

The predictability of unit hydrograph (UH) models that are based on the concepts of land morphology and isochrones to generate direct runoff hydrograph (DRH) were evaluated in this paper. The intention of this study was to evaluate the models for accurate runoff prediction from ungauged watershed using the ArcGIS R tool. Three models such as exponential distributed geomorphologic instantaneous unit hydrograph (ED-GIUH) model, GIUH based Clark model, and spatially distributed unit hydrograph (SDUH) model, were used to generate the DRHs for the St. Esprit watershed, Quebec, Canada. Predictability of these models was evaluated by comparing the generated DRHs versus the observed DRH at the watershed outlet. The model input data, including natural drainage network and Horton's morphological parameters (e.g. isochrone and instantaneous unit hydrograph), were prepared using a watershed morphological estimation tool (WMET) on ArcGIS R platform. The isochrone feature class was generated in ArcGIS R using the time of concentration concepts for overland and channel flow and the instantaneous unit hydrograph was generated using the Clark's reservoir routing and S-hydrograph methods. An accounting procedure was used to estimate UH and DRHs from rainfall events of the watershed. The variable slope method and phi-index method were used for base flow separation and rainfall excess estimation, respectively. It was revealed that the ED-GIUH models performed better for prediction of DRHs for short duration (≤6 h) storm events more accurately (prediction error as low as 4.6-22.8%) for the study watershed, than the GIUH and SDUH models. Thus, facilitated by using ArcGIS R , the ED-GIUH model could be used as a potential tool to predict

Journal of the American Water Resources Association, 2003

A synthetic triangular hyetograph for a large data base of Texas rainfall and runoff is needed. A hyetograph represents the temporal distribution of rainfall intensity at a point or over a watershed during a storm. Synthetic hyetographs are estimates of the expected time distribution for a design storm and principally are used in small watershed hydraulic structure design. A data base of more than 1,600 observed cumulative hyetographs that produced runoff from 91 small watersheds (generally less than about 50 km 2 ) was used to provide statistical parameters for a simple triangular shaped hyetograph model. The model provides an estimate of the average hyetograph in dimensionless form for storm durations of 0 to 24 hours and 24 to 72 hours. As a result of this study, the authors concluded that the expected dimensionless cumulative hyetographs of 0 to 12 hour and 12 to 24 hour durations were sufficiently similar to be combined with minimal information loss. The analysis also suggests that dimensionless cumulative hyetographs are independent of the frequency level or return period of total storm depth and thus are readily used for many design applications. The two triangular hyetographs presented are intended to enhance small watershed design practice in applicable parts of Texas. (KEY TERMS: surface water hydrology; hyetograph; design storm; small watersheds).

Journal of Hydrology, 1974

Heerdegen, R.G. and Reich, B.M., 1974. Unit hydrographs for catchments of different sizes and dissimilar regions. J. Hydrol., 22: 143--153.

Environmental Monitoring …, 2011

Hill torrents cause a lot of environmental and property damage in Pakistan every year. Proper assessment of direct runoff in the form of hill torrents is essential for protection of environment, property, and human life. In this paper, direct surface runoff hydrograph (DSRH) was derived for a large catchment using the geomorphologic instantaneous unit hydrograph concept. The catchment with hill torrent flows in semi-arid region of Pakistan was selected for this study. It was divided into series of linear cascades and hydrologic parameters required for Nash's conceptual model, and were estimated using geomor-phology of the basin. Geomorphologic parameters were derived from satellite images of the basin and ERDAS and ArcGIS were used for data processing. Computer program was developed to systematically estimate the dynamic velocity, its related parameters by optimization and thereby to simulate the DSRH. The data regarding rainfall-runoff and satellite images were collected from Punjab Irrigation and Power Department, Pakistan. Model calibration and validation was made for 15 rainfall-runoff events. Ten events were used for calibration and five for validation. Model efficiency was found to be more than 90% and root mean square error to be about 5%. Impact of variation in model parameters (shape parameter and storage coefficient) on DSRH was investigated. For shape parameter, the number of linear cascades varied from 1 to 3 and it was found that the shaper parameter value of 3 produced the best DSRH. Various values of storage coefficient were used and it was observed that the value determined from geomorphology and the dynamic velocity produced the best results.

Journal of the Civil Engineering Forum

Flood forecasting at Wonogiri Reservoir is restricted on the availability of hydrologic data due to limited monitoring gauges. This issue triggers study of unit hydrograph modeling using Geomorphological Instantaneous Unit Hydrograph (GIUH) which is based on Geographic Information System (GIS). Analysis of physical watershed parameters was conducted on Digital Elevation Model (DEM) data using software Watershed Modeling System (WMS) 10.1 and ArcGIS. Nash model and S-curve method were used to process triangular GIUH into hourly Instantaneous Unit Hydrograph (IUH) and Unit Hydrograph (UH) and then was compared with the observed UH of Collins method. A sensitivity analysis was conducted on parameter of RL and Nash-model k. Evaluation of accuracy of the simulated GIUH runoff hydrograph was also conducted. The GIUH model generated UH with smaller peak discharge Qp, also slower and longer of tp and tb values than the observed UH. Accuracy test of the simulated GIUH runoff hydrograph using...

Environmental Modelling & Software, 2008

In recent years, geomorphological instantaneous unit hydrograph (GIUH) approach to estimate the runoff from a watershed due to different storm patterns has gained wide acceptability for watersheds with scanty data. In this study, a user-friendly event based computerized GIUH model, GIUH_CAL, was developed. GIUH_CAL model incorporates an infiltration component. Depending on the availability of soil and infiltration data, the model offers a choice among three methods of infiltration calculation, viz., Richards' equation, phi-index method and Philip two term model. The graphical user interface (GUI) of the model is based on mouse-driven approach with pop-up windows, pull-down menus, sub-menus, toolbar, statusbar and button controls including comprehensive context-sensitive help file. GIUH_CAL model displays generated instantaneous unit hydrograph (IUH), unit hydrograph (UH) and direct runoff hydrograph (DRH) of the watershed graphically and processes statistically. Modelling efficiency (ME), coefficient of residual mass (CRM), root mean square error (RMSE) and coefficient of determination (r 2 ) are used as the performance criteria. The model was tested for two distinctly different watersheds, i.e., a 4th order Guptamani watershed in tropical sub-humid region and a 3rd order Upper Chhokeranala watershed in semi-arid region of India. The results show that model performs satisfactorily for both test watersheds and performance is much better with Richards' equation option of infiltration calculation as compared to phi-index method and Philip two term model.Thus, GIUH_CAL model can be adopted as a standard tool for modelling rainfallerunoff transformation process in scantily gauged watersheds.

Open-file report /, 1997

Contents III IV Contents 16=6 miles, main channel slope: 3.13-55.3 feet per mile, and percentage of impervious cover: 7.32-40.6 percent). The estimation equations are most reliable when applied to watersheds with SJ areas less than 25 mi .

Human, Riparian, and Aquatic Communities, 2000

The basic principles underlying the most commonly used physically-based models of the rainfall-runoff transformation process are reviewed. A thorough knowledge of these principles is a pre-requisite for flood hazard studies and, thus, this chapter reviews several physically-based methods to determine flood discharges, flow depths, and other flood characteristics. The chapter starts with a thorough review of linear system theory applied to the solution of hydrologic flood routing problems in a spatially aggregated manner --Unit Hydrograph approaches. The chapter then proceeds to a review of distributed flood routing approaches, in particular the kinematic wave and dynamic wave approaches. The chapter concludes with a brief discussion about distributed watershed models, including single event models in which flow characteristics are estimated only during the flood, and continuous event models in which flow characteristics are determined continuously during wet periods and dry periods.