Soil erosion and sediment yield from watershed are among key limitations to achieve sustainable land use and to maintain the water quality. Development of the sediment GRAPH (SG) is essentially required for accurate estimation of sediment yield from the watershed. However, development of SGs for watersheds is a tedious and time consuming task. Development of the sediment GRAPH models based on easily accessible physical characteristics of a watershed and precipitation data is therefore a viable and convenient tool for designing the efficient soil and water conservation measures. In this regard, driving synthetic SGs using INSTANTANEOUS UNIT sediment GRAPH (IUSG) is an applied approach in watersheds where detailed discharge and sediment data are not available. However, the performance of this approach in watershed scale with different governing conditions has rarely been evaluated. The present study formulated IUSG for Kojour watershed comprising an area of some 500 Km2. The Watershed located at east of Nowshahr City in Mazandaran Province, northern Iran. The suspended sediment samples were taken from Kojour River during eight storm events in 2008 and corresponding SGs were then developed. The results showed that the IUSG model is unable to predict observed SGs components of peak, time to peak, total sediment yield, and the base time having respective estimation errors of 764, 111,750 and 101%.

The usage of GEOMORPHOLOGIC parameters for estimating of UNIT HYDROGRAPH are a basic role in hyrological science. Due to lack of observed data in basins. Relationship between HYDROlogy and GEOMORPHOLOGIC parameters can lead to estimate HYDROlogic response of a basin. Dynamics and static parameters such as velocity and rainfall intensity plus bifraction ratio length ratio, area ratio length and slope of the main stream affect on response of basin. To make relation between these two elements can estimate the output HYDROGRAPH of a basin. In this research project by this method for representative basin of Kasilian in north Iran HYDRO GRAPH were estimated and then by other synthetic methods such as Snayder, SCS and triangular SCS were compared. It is mentioned that the giuh by ROSSO method also acquised. After then these methods compared by observed HYDROGRAPH, the result was satisfied and they have no significant differences.

Given the increasing trend of application of GeoGRAPHic Information System (GIS) for natural resources study in one hand and complication of biological, GEOMORPHOLOGICal, HYDROlogical and ecosystem mechanisms on the other hand, scale is an overlooked but very impressive and flourishing concept. As for any natural resources study consistent with its phase, various maps are used and produced so in order to make the achieved results usable for planning as well as management of resources, determination of scale of the study and application domain for the results is very significant. Since using GIUH model in the basins without HYDROlogical data have been widely recommended by HYDROlogist and this model developed in accordance to the relationship between GEOMORPHOLOGICal properties of basins and their effects on HYDROlogical responses, so before using that it is essential to determine the optimal scale (in view points of accuracy, time and cost) which in this paper will be selected from 1: 50000 and 1: 25000 scales, inclusively used in topoGRAPHic maps in Iran, using multi-scale analysis. Of course, it should be mentioned that giving a comparison between the results of GIUH and the recorded data as well as the model’ s effectiveness in our research basin has not been the purpose.

Estimating the runoff in the basins lacking statistics is always considered by researchers And managers in planning, development and implementation of many projects of water Resource. One of the methods for estimating the runoff is to use geomorphology INSTANTANEOUS UNIT HYDROGRAPH which estimates the HYDROGRAPH of flood based on quantitative geomorphology factors. In this study, first the quantitative geomorphology of the Nash and Rousseau methods including k (scale parameter), n (shape parameter) and speed (Meters per second) were obtained. In the next step, INSTANTANEOUS UNIT HYDROGRAPH was obtained by GIUH method and ultimately flood HYDROGRAPH was created for 20 selected events from 1991 to 2007 in kasilian region and compared to the observational HYDROGRAPHs. Through sensitivity analysis, infiltration Index (φ ) had higher sensitivity analysis, infiltration Index (φ ) had higher sensitivity and n (Parameter of shape) were less sensitive. Also, by comparing peak discharge values and computational HYDROGRAPH widthsin the state where the discharge of HYDROGRAPHs is 50 and 75% of peak discharge, observational data revealed that the Rousseau method and lower error than the Nash method and Nash method had a higher accuracy than Rousseau in terms of the volume and time.

Among the main objectives in HYDROlogy are to quantitively forecast 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 ungaged watersheds. If the dimensions of flood HYDROGRAPH (which is the result of the watershed response to rainfall) are known, then the importance of models which are based on geomorphology of a basin will be very clear. The purpose of this study is to investigate the consistency, accuracy and reliability of GEOMORPHOLOGICal and geomorphoclimatical models in estimating the shape and discharge of flood resulting from a rainfall with certain intensity and duration. The results of these two models were compared with Nash, Rosso and SCS models. The results showed that the efficiency of GEOMORPHOLOGIC model ratio to geomorphoclimatic, Nash, Roso and SCS are 106.56, 171.12, 106.79 and 112.64 percent respectively, and that geomorphoclimatic model ratio to Nash, Rosso and SCS is 106.57, 100, 21 and 105.69 percent, respectively. Therefore, the result of GEOMORPHOLOGIC model compared to other models (based on this study) is the most efficient model to estimate flood discharge.

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 study of relations between morphologic characteristics of basins and their HYDROlogic response is one of the important issues in the science of HYDROlogy. GEOMORPHOLOGIC INSTANTANEOUS UNIT HYDROGRAPH (G.I.U.H) and Geomorphoclimatic INSTANTANEOUS UNIT HYDROGRAPH (Gc.I.U.H) and GRAY UNIT HYDROGRAPH are some results of the efforts in this field in order to evaluate the efficiency of these models in determination of the shape and ordinates of direct runoff HYDROGRAPH, Navrood representative basin in southwest ledge of Caspian Sea in west of Gillan Province was considered. Database of 6 events of rainfall-runoff in non-melting seasons was collected. Ordinate of UNIT HYDROGRAPH and direct runoff HYDROGRAPH were calculated by using the above models for selected events, separately. The results show that G.I.U.H and Gc.I.U.H models in comparison with GRAY model are better fit for use in determination of peak discharge in direct runoff HYDROGRAPH but there is no significant difference among them in determination of time to peak, base time and volume of direct runoff. In addition, Gc.I.U.H model in comparison with G.I.U.H is of a higher efficiency for determination of the ordinates of direct- runoff HYDROGRAPH especially in cases with less peak discharge.

INSTANTANEOUS UNIT sediment GRAPH (IUSG) is one of the methods for predicting sediment GRAPH of the flood events and its application needs to estimation of storage coefficient (Ks), dimensionless shape factor (ns), time to peak (tp) and INSTANTANEOUS sediment supply. Investigation of relationships among the mentioned parameters and rainfall and water discharge characteristics could facilitates use of IUSG in ungaged drainage basins. In this research concurrent flow and sediment discharge of five flood events in Poledouab HYDROmetric station monitored hourly .IUSG parameters calculated using observed sediment GRAPHs and rainfall hyetoGRAPHs and their relationship investigated with excess rainfall and peak water discharge of flood events. The results show that correlation coefficient (r2) of power regression equation between Ks and rainfall excess is greater than peak flow (0.79 and 0.42).dimensionless shape factor of ns shows statistically weak relationship with rainfall excess and peak flow but its ratio to time to peak of sediment GRAPH (ns/tp) resulted in statistically meaningful relationship with the rainfall excess and peak flow (respectively 0.85 and 0.67 of r2).application of the obtained equations in this research for predicting sediment GRAPH of some flood HYDROGRAPHs and comparing the results with the sediment rating curve methods show that rising limb of the sediment GRAPH could be predicted more accurately than falling limb of sediment GRAPH.

Applications of rainfall-runoff models, are to determine the HYDROlogic behavior of watershed and to simulate the flow, for designing hydraulic structures and specially evaluating the impacts of operations on the flow regime. According to deficiency of HYDROmeter data in most of Iran’s watersheds, using simple and convenient HYDROlogic models and developing them for watersheds without stations is essential. In this context, several methods have been proposed.This study has been compared the consistency, accuracy and reliability of GEOMORPHOLOGIC, geomorphoclimatic and nash INSTANTANEOUS UNIT HYDROGRAPHs, in estimating outlet runoff HYDROGRAPH characteristics, in Manshad watershed.For this purpose, six storm events were chosen, by using the area’s HYDRO-meteorological data. Then, the methods’needing parameters, including the area’s morphometric characteristics and the events properties, were calculated.Thus, outlet runoff HYDROGRAPHs, for each method were determined. Evaluations that have been carried out by using the mean relative error, the root mean square error and the Nash-Sutcliffe indices, confirmed the higher efficiency of Nash model, in estimating peak discharge, with an error of 23.75, time to peak with an error of 28.21 and the complete shape of HYDROGRAPH, with efficiency criterion of 0.4, than the other methods. In addition, this method has a high potential in simulating the actual amount of flood volume, with an error of 9.90. Thus, nash model, compared to other models (based on this study), is the most efficient mod el for estimating flood discharge.

The INSTANTANEOUS UNIT HYDROGRAPH (IUH) concept is widely applied for runoff estimation in watersheds with scanty data. In this paper, the method of GEOMORPHOLOGICal UNIT HYDRO GRAPH of reservoir (GUHR) was applied to Liqvan watershed located in East Azarbaijan, Iran. This method is based on the cascade of linear reservoirs which are assumed to contain the stream flow of related sub-watershed area. Hence sub-basins are replaced with consecutive reservoirs according to watershed geomorphology. Indeed the model is the routing of flood through these reservoirs and to determine the UNIT HYDRO GRAPH in the basin outlet. The results showed GUHR has efficiency enough in simulating the rainfall-runoff by the use of watershed GEOMORPHOLOGIC characteristics of a basin. The sensitivity analysis of model was carried out by changing the parameter values. Results showed that to decrease in K values caused to increase in the peak of HYDRO GRAPH (qp) with less time of peak (tp) and vice versa.