The present study has been conducted to evaluate the efficiency of Clark Instantaneous Unit Hydrograph Model in regenerating Flood unit Hydrograph in Bazoft watershed in Chaharmahal and Bakhtiari Province. The comparative evaluation is conducted between the 2h-Unit hydographs simulated using Clark model and the one obtained from averaging the observed ones. This comparison is made with the help of statistical criteria viz. relative error, root mean square of error, coefficient of efficiency and bias. It verified high level of compatibility between two unit Hydrographs using the dark model and the Hydrograph obtained by averaging the observed data.

Flood Hydrograph is a one of most important component in hydrological and hydraulics analysis. Estimation of Design Flood with consideration uncertainty of random variable is important in Design of hydraulic structure. In conventional method, peak of Design Flood is estimated by use of frequency analysis.In this approach uncertainty of other variable such as rainfall, loss and base flow is missed. In this paper Flood Hydrograph is generated in Jamishan dam catchment with consideration of uncertainty of random variable by use of combination of RPG model, HEC-HMS and Monte Carlo simulation. Result is shown; methodology that be used in this paper has good accuracy to Flood Hydrograph generation and 100 percent of volume, peak and Hydrograph of Flood is located in confidence band.

Flood Hydrograph simulation is affected by uncertainty in Rainfall - Runoff (RR) parameters. Uncertainty of RR parameters in Gharasoo catchment, part of the great Karkheh river basin, is evaluated by Monte-Carlo (MC) approach. A conceptual-distributed model, called Monte- Carlo, was used for basin simulation, in which the basin's Hydrograph was determined using the superposition of runoff generated by individual cells dividing the catchment in a raster-based discretization. A narrow parameter range was obtained through application of the MC method. Parameter range depended on goodness -of-fit measures. The results of various goodness-of-fit measures are discussed in this paper. The selected goodness-of-fit measures gave high weight to peak discharge to reduce peak discharge error.

Efficacy in estimation of storage coefficient in Clark method, as one of the applicable techniques for development of instantaneous unit Hydrograph, may have great effect on ultimate unit Hydrograph. The present study was therefore conducted in Bazoft watershed in Chaharmahal and Bakhtiari Province to determine the efficiency of developed Hydrograph using Clark method and to compare the Muskingum storage coefficient obtained through graphical, Clark and Linsley methods. Firstly, the time-area histogram of the watershed was developed. The 2h-unit Hydrograph was then derived using the data collected in Chelgerd climatological and Morghak hydrometric stations. The efficiency of Clark's instantaneous unit Hydrograph developed based on graphical, Clark and Linsley methods for calculation of Muskingum storage coefficient was ultimately evaluated. The results of the study revealed that the Clark's instantaneous unit Hydrograph resulted from graphical method for estimation of storage coefficient is more compatible with average unit Hydrograph existed for the watershed than other two methods.

Among the main objectives in hydrology are to forecast quantitatively the process of rainfall-runoff, and to determine Flood discharge at the outlet of a watershed. Flood discharge can be estimated using rainfall-runoff models which explain hydrological phenomena for unmeasured watersheds. Relationship between hydrology and geomorphologic parameters can lead to the estimate of hydrologic response of a basin. The purpose of this study is to investigate the consistency, accuracy and reliability of geomorphologic model (GIUH) in estimating the shape and discharge of Flood resulting from a rainfall with certain intensity and duration. The results of this model were compared with SCS (Soil Conservation Service), Snyder, triangular, Rosso and Geomorphoclimatic (GCIUH) unit Hydrographs. The results showed that in Kasilian basin with the area of 67/78 km2, GIUH model had the least amounts of main relativity (MRE) and square error (MSE). Furthermore the result showed that the efficiency of geomorphologic model ratio to Snyder, SCS, Triangle, Rosso and GCIUH in Kasilian Basin are 91.06, 99.11, 88.642, 48.19 and 4.94 respectively. Therefore the result of Geomorphologic model compared to other models (based on this study) is the most efficient model to estimate Flood discharge.

The Clark method is one of the most applicable techniques for development of instantaneous unit Hydrograph whose efficacy depends upon the accuracy in estimating storage coefficient. The present study was conducted in Kasilian watershed in Mazandaran Province to determine the efficiency of developed Hydrograph using Clark's method and to compare the Muskingum storage coefficients obtained through graphical, Clark, Linsley, Mitchell, Johnstone-Cross and Eaton methods. To this aim, the time-area histogram of the study watershed was initially developed. The 3h-unit Hydrograph was then derived using the data collected in Sangedeh climatological and Valikbon hydrometric stations. The efficiency of Clark’s instantaneous unit Hydrograph developed based on 6 methods for calculation of Muskingum storage coefficient was ultimately compared with the observed average 3h-unit Hydrograph of the study area. The results of the study revealed that the Clark’s instantaneous unit Hydrograph obtained from graphical method for estimation of storage coefficient with estimation error of less than 33.33% and efficiency coefficient of 83% could suitably simulate different components of the observed average unit Hydrograph for the study watershed.

Accurate prediction of Floods is especially important in arid areas with more irregularities and intensities. Lack of hydrometric stations in these areas of our country, along with the important advantage of the GIUH model, which allows the simulation of precipitation-runoff of a basin with the least information data, led the researchers to evaluate the above model in the basin. Consider the catchment of Minab as their goal. The quantitative values ​​of each of the geomorphological parameters of the GIUH model, the most important of which are the bifurcation ratio, length ratio and area ratio, have been calculated using GIS technology and with the help of HECGeoHMS add-on. In ranking waterways, the Strahler method was used as a basis. The Hydrograph model of the geomorphology unit in the study basin has had acceptable results according to the calculated average error equivalent to 17. 22% for the peak discharge of 4 selected events. However, in estimating the peak occurrence time, the amount of error is higher and in all events, the peak discharge time is less than the real time. In addition, the results of this model in the same basin under study also provided acceptable results with an average error rate of about 30% in calculating the peak discharge. The GIUH in Minab catchment has had acceptable results according to the mean error calculated for the peak discharge of 4 selected events. Therefore, it is possible to achieve the desired results from this model in similar conditions and by applying changes.

Natural rivers experience significant sediment transport rates during Floods.The purpose of this study was to investigate the effects of Flood Hydrograph intensity parameter on the amount of bed sediment transport rate. For this purpose, a real unsteady flow Hydrograph was created inside a 15 meters long tilting flume by installing an interface board between the computer and the pump inverter. Sediments with a d50 of 2.69 mm have been put uniformly on the bottom of the channel and the Flood Hydrograph has been applied on it after saturation. 20 cases of Hydrographs with different intensity parameters were tested and the erosion rate was obtained during the Hydrograph time. The results show that the maximum erosion rate always occurs near the peak of the Flood Hydrograph and the time delay between the peak of the Flood Hydrograph and the peak of the sediment Hydrograph is mostly positive. The erosion rate in the rising limb of the Hydrograph is higher than the falling limb, and the distance between them decreases in the hysteresis diagram as the flow intensity parameter decreases. The changes of bedload transport rate (qb) in terms of flow rate (Q) are clockwise hysteresis. By decreasing the Hydrograph intensity parameter by 32, 57, 75 and 87%, the total volume of transferred sediments decreases by 27, 51, 78 and 90%, respectively. A 50% decrease in the base time of the Hydrograph under the same conditions has caused a 46% decrease in the total volume of transported sediments.

There are various models for Flood prediction that are based on different conceptual basis. The current SCS-CN model is a well-known model in this field that is widely used in Iran and other countries. Recent researches focuses on improvement of this model and improve its efficiency but it is necessary to evaluate the improved models for catchments of Iran. The objective of this study is the comparison of current SCS-CN and developed Mishra-Singh (One Parameter) models for Flood Hydrograph and peak estimation using data of five catchments in Golestan province...