جستجوی مقالات مرتبط با کلیدواژه « دبی اوج » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

The concentration time of catchments is one of the most important and common effective features in hydrological studies, particularly in determining the flow discharge for designing watershed management projects. Most of the catchments in the world especially in Iran were not equipped with hydrometric stations, and project managers are forced to use traditional empirical models to estimate concentration time and peak flow. The review of previous studies shows that experimental models for estimating concentration time have unfavorable results due to the change of environmental conditions outside the place where the model is presented. On the other hand, there is not enough information about the effectiveness of experimental models for estimating concentration time in many catchments in Iran, especially in semi-arid areas. The purpose of this study is to evaluate the accuracy of some experimental models for estimating concentration time in the sub-basins of the semi-arid region of the northwest of the country and to identify its determining factors.

This study was conducted in eight sub-basins including Alanagh, Ordakloo, Shekaralichay, Shiramin, Kurjan, Kalaleh and Livar from Urmia Lake and Araz River basins in Northwest Iran. Meteorological and hydrometric data were obtained from the Natural Resources of East Azerbaijan and stations belonging to the Ministry of Energy. The characteristics of the basin such as area, length, slope, height and shape were determined through field studies and drawing maps in the GIS platform. The concentration time was calculated using the hydrograph of the flows in the statistical period of 30 years (from 1367 to 1397) and it was estimated through six experimental models including Kirpich (1940), Kerby (1959), Chow (1962), Federal Aviation Administration (1972), Bransby-Williams (1980) and Ventura (2007). The relationship between concentration time and catchment characteristics was investigated by correlation matrix, Pearson's method. Nash-Sutcliffe efficiency coefficient, average error and root mean square error were used to evaluate the accuracy of the models.

According to the results, Shekaralichay sub basin has the shortest (66 minutes) and the Kalaleh sub basin has the longest concentration time (132 minutes). Bransby-Williams model had the lowest error (6.8 %) and the highest efficiency coefficient (73%); while the estimation error (36.2 %) and the Nash-Sutcliffe efficiency of Federal Aviation Administration model were 36.2% and-14.4% respectively. The slope was the most important main factor on the estimation of concentration time of the assessment in the Kirpich model (r= 0.83), Chow (r= 0.82) and Bransby-Williams (r= 0.73). Federal Aviation Administration model (1972) and Ventura model (2007) have a weak estimate in sub-basins with low slope and length.

The results showed that among the physical characteristics of the basin, the area, slope and length of the sub-basin play a more important role in changes in concentration time. This study showed that the slope percentage of the basin is the most important factor in reducing concentration time, peak discharge and increasing the speed of flooding in the studied sub-basins, so it is suggested to use soil protection plans in order to increase the concentration time for sub-basins that have a higher slope percentage. The evaluation of concentration time estimation models in eight catchments showed that the Bransby-Williams (1980) model with an average error of 6.80% and Nash-Sutcliffe efficiency coefficient of 73% provides the best estimation among others, so the use of this model in similar basins which do not have measuring stations, it is suggested.

Due to the heterogeneity in watersheds and the non-linearity of hydrological behaviors, it is very complicated and difficult to fully understand the relationships within watersheds. Therefore, in evaluating these systems, a modeling process is necessary. Over the last few decades, hydrological/hydraulic models have become essential in hydrology studies due to the development of programming languages and the provision of optimal and efficient algorithms for solving differential problems. The application of rainfall-runoff simulation models for flood events has been extensively studied by researchers in the field of water and soil protection, leading to the development of various models to simulate rainfall-runoff processes. One of the successful models in this field is the TOPKAPI-X model. This model was created in the 1990s at the University of Bologna by Professor Todini as a distributed rainfall-runoff model in watersheds. An important feature of distributed models is their ability to simulate components at any point of the watershed, allowing results to be extracted at any required point. Unlike lumped models that consider the entire watershed as a single unit, distributed models allow spatial distribution at any point in the watershed. Therefore, in this research, after calibrating and validating the TOPKAPI-X physical-distributed model in the studied basin, the model was optimized for flood estimation.

The Gamasiab basin is located in the west of Iran, in the northern region of the Zagros mountain ranges, to the north of the Karkheh dam basin, and primarily within the territories of Hamadan and Kermanshah provinces. The mountainous regions of this basin are mainly concentrated in the northern and southern parts, while its lowlands and plains are mostly located in the middle and southeastern parts of the basin (Ministry of Energy, 2014). In this research, the TOPKAPI-X model was used to simulate floods in the Gamasiab watershed. First, the watershed boundary was delineated using a digital elevation model (DEM) with a resolution of 30 meters. Land use maps, soil texture, watershed network, and climatic components were entered into the TOPKAPI-X model. The outlet location of the basin (hydrometric station) was used to simulate the flow using the TOPKAPI-X distributed hydrological model. Continuous time series data on a daily time step were used in this rainfall-runoff model. Specifically, daily rainfall data from 13 rain gauge stations and temperature data from 4 synoptic stations during the statistical period (1999 to 2020) were used to simulate the flow. After running the model several times, the general parameters were manually adjusted each time until the optimal values of the general parameters were obtained by considering the appropriate values of the evaluation criteria (NS and Bias) for the basin.

This research was conducted to analyze the flood discharge of one of the main sub-basins of the Karkheh dam basin using the TOPKAPI-X model on a daily time scale. In the TOPKAPI-X software environment, simulations were performed during the calibration period using input maps and observational rainfall, temperature, and discharge data. A visual comparison of the observed and simulated hydrographs allows for a general and quick evaluation of the model's accuracy. The graphical results of the comparison between the discharge generated by the TOPKAPI-X model with the calibrated parameters and the measured discharge in the Gamasiab basin were presented. The TOPKAPI-X model has the ability to estimate the maximum daily flow rates of the Gamasiab basin; however, some of the simulated flow rates are higher than the observed flow rates. Four criteria—NSE, R, BIAS, and RMSE—were used to evaluate the model. The evaluation results of the TOPKAPI-X model indicate the accuracy of flow simulation, with a Nash-Sutcliffe criterion of 0.697 during the calibration period (1999-2014) and 0.660 during the validation period (2015-2020) for the Gamasiab basin. Therefore, it can be concluded that this model has good performance for flow simulation.

The importance and usefulness of hydrological models for water resources management, understanding hydrological processes, and conducting impact assessment studies is clear. Hydrological models are crucial tools that enable scientists and policymakers to make informed decisions based on simulations of watershed behavior. Considering the increasing demand for water and the impact of climate change, hydrological simulation will be one of the essential methods for future water management. The results of this study showed that the TOPKAPI-X model has potential in simulating runoff in the selected basin. Due to the capabilities of the TOPKAPI-X distributed hydrological model, this software is recommended as a modeling tool for other basins.

Flooding is one of the environmental hazards that causes a lot of repeated damage to water and soil resources in different regions of Iran and around the world. Check dams as a mechanical practice have been built in many watershed areas of the country to control peak discharge and prevent soil erosion. Therefore, it is essential to examine the role of these mechanical practices in flood control at the level of watersheds. The current study aims to investigate the effect of the construction of three proposed structures (two masonry check dams and one embankment dam), with spillway heights of 9, 6, and 8 meters, on flood characteristics in Kander Abdolreza watershed, Fars province, Iran. In other words, this study examines whether the construction of these three consecutive structures fulfills the goal of the operation, which is flood control through a significant reduction in peak discharge and flood volume in the study area. Therefore, the most important variables in this study is the flood volume and the volume of reservoirs proposed for flood control. The amount of flood volume is extracted from the flood hydrograph, and the volume of reservoirs is obtained using a contour map and storage-height curves. It is obvious that if the volume of the reservoir is more than the volume of the flood, all the flood will be attenuated by the structure and the runoff would not pass through the spillway of the dam. 

In this study, the HEC-HMS model was used to simulate the rainfall-runoff process and the reservoir effect of each of the three proposed consecutive check dams on flood characteristics. The study area, Kander Abdul Reza watershed, is located about 27 kilometers southeast of Lamerd city, Fars province, Iran. According to the division of watersheds in the country, it is part of the Kol-Mehran basin which is a subbasin of the major basin of the Persian Gulf and Oman Sea. In this regard, after preparing the required data, including properties related to topography, rainfall, soil hydrologic group, and designed structures, the peak discharge and volume of flood under different return periods were estimated using the HEC-HMS model. Ghahreman-Abkhezr method was also used to estimate the intensity of rainstorms. The characteristics of the flood in the downstream were investigated in the absence of three proposed structures (two masonry check dams and one embankment dam) and in the next step, the effect of these reservoirs/dams on the hydrograph of the flood was analyzed. Due to the fact that the proposed structures are located upstream of the residential area and the highway, the basis of the design of the structures was the flood discharge with a return period of 100 years. Finally, using the obtained results, the percentage of reduction in the peak discharge of the flood under the influence of the construction of each of the reservoirs/dams was determined and compared.

The outcomes of SCS unit hydrograph for Kander Abdolreza watershed showed that the flood peak discharge in the return period of 2, 5, 10, 25, 50, and 100 years is equal to 7, 32, 46, 72, 91, and 116 m3.s-1, respectively; so that the time base of the hydrograph varies from 6.5 hours in the 2-year return period to nearly 9 hours in the 100-year return period. Meanwhile, the volume of runoff varies from 1.73 m3 in the return period of 2 years to 1053 m3 in the return period of 100 years. The results also showed that if the three proposed three consecutive structures were built, with a total reservoir volume of 614367 m3, the peak flood discharge would fall from 116 m3.s-1 to 32 m3.s-1 over a 100-year return period. In addition, the outcomes of the simulation of the rainfall-runoff process in the study watershed indicated that the reduction in the peak discharge and volume of the flood after the implementation of the proposed structural measures for the 50-year return period was 84% and 73%, respectively; and for the 100-year return period it was reduced by 72% and 57%, respectively. Thus, according to the results of the simulation of the effect of the designed structures, it can be claimed that the proposed structures for the study watershed would have the ability to mitigate and control floods.

The implementation of the proposed structural measures for the Kander Abdolreza watershed, including two masonry check dams and one embankment dam, in addition to reducing the peak discharge and the volume of flood flows, can stabilize the longitudinal profile of the stream channels, which is useful for the conservation of soil and water resources in the study area. At different return periods (2, 5, 10, 25, 50, and 100 years), the three proposed structures have the required capacity to store runoff and reduce the peak discharge in the study watershed; however, as the return period increases, the role of these reservoirs/dams in controlling the flood and reducing the peak flow decreases. Moreover, the effect of the proposed consecutive structures system on peak flow reduction is greater than the effect of these structures on flood volume reduction.In general, to increase the effectiveness of the watershed studies plans, it is recomended to include the study of the impact of the implementation of structural measures on the characteristics of flood flows in the service description worksheet of these projects so that the decision to carry out or not to carry out for structural operations in each basin or sub-basin is made based on the simulation results and with more detailed information. In addition, to better evaluate the proposed structural measures for flood control, it is suggested to prioritize the installation of hydrometric stations in ungauged watersheds that are prone to flood generation.

The development of residential and urban areas on the banks of rivers and flood plains, regardless of the hydraulic and hydrological conditions govering the upstream basin and the river, increases the risk of flooding. Therefore, the study of floods for the purposes of planning, optimal exploitation and management of this natural phenomenon is one of the important issues in water resources management. The current research aims to investigate the rate of land use change using the HEC-HMS hydrological model and geographic information system (GIS) and Landsat satellite images during the years 1991, 2001 and 2011 in the Rigan watershed of Kerman province with an area of 7091 square kilometers. It was investigated on the increase of flooding of surface runoff in the area. For this purpose, in the first step, satellite images were interpreted and processed, and changes in land use was determined and soil CN values were calculated. Then, with the help of HEC-HMS model, the rainfall-runoff process in this basin was simulated and the peak flood discharge values were obtained in each period, and finally the flood hydrograph of the watershed was estimated. The results showed that with the increase of urban impervious surfaces and destruction of agricultural lands and pastures in the study area, the rate of soil CN from 1991 to 2011 increased from 65.28 to 70.25, following which the peak flood discharge from 29 m3 / sec in 1991 to 29.3 m3 / sec In 2011 and also the volume of runoff has increased from 3.4 to 6 mm during this period. The obtained results can be of great help to the implementation of watershed projects.

In recent years, extensive practices have been done on flood control, erosion and sediment in the fields of research and implementation of watershed management. Therefore, the purpose of this study was to assess the effects of watershed management practices on the characteristics of runoff and suspended sediment load in two subwatersheds in Ghaleh Gol watershed in Lorestan province, Iran. In this research, for comparing the effect of watershed management practices (WMP) on discharge and suspended sediment load (SSL) from both subwatersheds, the flow velocity was measured and the SSL was sampled directly from the beginning of the rainfall events until the end of them. Results showed that in all measurements, the discharge and suspended sediment load of the southern subwatershed with watershed management practices was higher than the northern subwatershed without such practices. According to the results of ANOVA test, it was found that the difference between discharge peak (P=0.691) and suspended sediment load peak (P=0.840) was not significant in two subwatersheds. Also, according to the results, the difference between specific discharge and specific SSL was not significant (P>0.05). Based on these results, it was found that the implementation of WMP in the study area apparently has no the required performance to reduce the discharge and SSL, and the WMP have lost their performance before the end of their useful life. Therefore, in order to increase the performance of mechanical watershed management practices (MWMP), the biological and biomechanical practices has to be performed simultaneously.

Flood hazard assessment is an important topic that can reduce flood-related losses. Rainfall-runoff modeling plays a key role in the management of water resources in addition to protecting from flood hazards. The use of hydrological models to simulate the runoff necessitates the proper calibration of the different parameters. Therefore, In the present study, the Watershed Modeling System (WMS11.0) was evaluated to simulate peak discharge and volume of floods of Babolrood catchment. WMS model calibrated and validated using 3 and 2 rainfall events, respectively. Afterwards, design precipitation (DP) for 2, 5, 10, 25, 50, 100 and 500-year return periods was determined and flood resulting from DPs simulated. The results showed that the WMS model could accurately estimate the peak discharge (the error was about 5%) and the and flood volume (the error was less than 26%). But the model was not able to simulate properly the shape of the hydrograph. It also revealed that peak discharge and flood volume arising from 2 to 500-year return periods of rainfall vary between 50 to 300 m3/s and 6.6 to 32.4 Mm3, respectively.

Various problems regarding watershed issues that have occurred because of human activities and economic development, are attracting increasing attention. Subsequently, many researchers are concerned about the effect of land use change on runoff which depends on the size, average slope, and the watershed’s baseline land cover characteristics. Moreover, the extent of the land-use change effect on simulated runoff depends on the hydrological model used and the processes considered in this regard. Any change in Land Cover and Land Use (LCLU) would affect the runoff characteristics of a drainage basin to a great extent, which, in turn, influences the region’s surface water and groundwater availability, leading to further changes in LCLU. Therefore, it is necessary to evaluate the effect LCLU changes on a region’s runoff characteristics in general and on small watershed levels (sub-basin levels) in particular.Land use changes in developing countries usually affect forests and national reserves. This is due to human activities such as creating settlements, developing agriculture, and encroaching on forestlands. Poor hydrological measuring infrastructure and lack of expertise are amongst the main factors which prevents a comprehensive analyses of catchment scenarios and their impact on the environment. Changes in climate and land use/cover (LUC) play an important role in altering the runoff trend. Climate change influences the runoff and the regional water balance by affecting precipitation and temperature rates. While precipitation is particularly crucial in determining the amount of water for runoff, temperature mainly affects evapotranspiration, which is regarded as a kind of loss for runoff formation. Moreover, changes in LUC influence the runoff routing trend.For instance, the destruction of a forest may affect soil permeability and further alter the runoff generation trend. On the other hand, an increase in impermeability of the surface areas’ soil because of urbanization can decrease the infiltration rate and concentration time, leading in turn to an increased in surface runoff. As changes in runoff considerably affect water resources, investigation of the runoff responses to climate and LUC changes is essential for the preservation pf local ecology and sustainable utilization of water resources. Furthermore, environmental scientists and local planners need a model for estimating the impacts of land-use change on groundwater recharge, water supply, and wetland hydrology.There are several evidences indicating that changes in land cover have influenced the hydrological regime of various river basins. Furthermore, the effects of climate change on hydrological cycle and the runoff behavior of river catchments have largely been discussed in recent years. However, it is currently not clear how, to what extent, and at which spatial scale such environmental changes are likely to affect storm runoff generation, and consequently on the rivers’ flood discharges. Changes in Land Cover and Land Use (LCLU) affect to a great extent the runoff characteristics of a drainage basin, which in turn, influence the surface and groundwater availability of the area, leading to further change in LCLU.Land use/land cover (LULC) change is a dynamic and complex process that can be exacerbated by a number of human activities, including an increase in human population and population response to economic opportunities. While in the past, the rivers’ corrective operations were focused on building constructs for controlling the rivers’ flow and implementing construct operations, hydrological consequences of climate change and land use changes, flood plains’ economic and ecological developments, and the alteration of social views regarding rivers’ safety and ecological functions have directed the attentions to the more sustainable use of rivers. Unfortunately, river systems have not been monitored with sufficient spatiotemporal resolution over long periods to deal with the above-mentioned issues through field observations alone. Therefore, to make appropriate management decisions for watershed basins, the effect of land use change on runoff should be evaluated based on hydrological models.

To assess the impact of land use changes on the Khorramabad watershed’s hydrological behavior, land use map, CN and the runoff coefficient maps was prepared for 1985, 2000, and 2016, using Landsat satellite imagery. Moreover, HEC HMS computer model was used for modeling rainfall-runoff. 

The study’s results showed that the change in the region’s land use, especially the reduction of forest lands and increase of urban areas, has led to an increase in peak-flow discharge, an increase of runoff volume, the reduction of concentration time and lag time, the reduction of the time required for reaching the hydrograph time, and decrease of the watershed’s runoff, with the watershed’s peak discharge changed by 54.195 to 150 percent in 1985-2000 period, 82.867 to 210.714 percent in 1985-2016 percent, and 18.594 to 24.285 in 2000-2016, period, and the concentration time and the flood’s peak discharge time changed by -6.99 and -5.02 percent in 1985-2016 period, respectively. Furthermore, the results of implementing the model on precipitations with return periods indicated that with an increase in return time, the amount of discharge changes decreased. For instance, in 1985- 2016 period, the increase in the discharge rate in return times of 2 and 100 years was 22.55 and 16.87, respectively.

Land use changes vary in different parts of a land, including the conversion of forest lands to agricultural ones, ranch and agricultural lands to residential and urban areas, and agricultural lands into abandoned ones. In the north and northwestern part of the basin, severe destruction of forests and their conversion to agricultural lands, and in the south and southwestern part of the basin, the conversion of agricultural and rangeland lands into residential and urban areas was observed. Moreover, CN has particularly increased in these areas under the influence of land-use changes.

Flood is one of the natural hazards that causes numerous financial and life damages each year. Therefore, flood potential prioritizing is crucial to reduce the damages caused by it. The aim of this study was to evaluate the efficiency of the Analytic Hierarchy Process (AHP) in flood potential prioritizing of Barajin sub-catchments. So, flood potential of sub-catchments was determined using AHP and the results are compared with the outputs of the HEC-HMS model as observed data. The results showed that in addition to full compliance of the two maps, there is a significant correlation (0.9299 and 0.934) between flooding potential ranks and peak flood discharge ranks with the return periods of 25 and 50 years of sub-catchments. The weights of AHP were also showed that in the flood of sub-catchments, generally, hydro-climatic criteria (weight = 0.65) is more important than morphometric criteria (weight = 0.35); and the rainfall intensity is the most important sub-criteria (weight = 0.373). Based on the final ranking, sub-catchments of 5, 3, and 4 that are located in upland and mountainous areas, have high flood potential due to the high weight of tow sub-criteria, one rainfall intensity, and the other 25-years rainfall. The results of this study could be a good guide for controlling floods of the study area in addition to understanding the processes governing the watershed.

Evaluation of the impacts of past watershed projects provides useful insights for future projects. In this study, the hydrology and water resources status of Akujan Catchment of Qazvin Province has been the object of the study in which the effects of various measures of watershed managements were evaluated. For this purpose, the changes of water resources discharge, increased infiltration, water storage, peaks and volumes of catchment floods, were compared before and after the implementation of watershed management projects. Results showed that 114000 m3</sup> more runoff storage has been carried out by watershed management operations that 20.1% of this volume was related to the structural operations and 79.9% of it was due to biological and biomechanical projects of the catchment. Results of the flood analysis indicated that the role of structural measures in the change of time of concentration is low and even negative. Therefore the reduction of the peak flow and flood volume at the outlet of the catchment is due to the implementation of biological and biomechanical measures which reduces the peak flows by 42.7, 25.4, 20.8, 17.1, 15.3 and 13.8% and flood volumes by 41.8, 24.8, 20.2, 16.5, 14.8 and 13.3% respectively for the return periods of two, five, 10, 25, 50 and 100 years. Another observation is that the effect of watershed management practices on the reduction of flood peak and volume decreases when the return period of flood is increased.

Peak flow estimation is one of the major issues in water resources and flood management that have basic role in the design of hydraulic structures and biomechanics activities in basins. So that a proper assessment has a basic role in the success of administrative works. In this paper, using artificial intelligence methods (MLP Neural Network, the mixture of SOFM with MLP, the mixture of FCM with ANFIS) to estimate Yalfan River’s peak discharge in hydrometer local station. For these models, eight variables have been considered as the inputs that includes rainfall amount in the occurrence time of flood, rainfall of five days ago from occurrence of flood, curve number of the basin (CN), basic discharge and finally peak discharge are considered as the output. In the artificial intelligences after preprocessing of the data, the optimal structure of the models are determined with input and output data, evaluation criteria and trial and error. At the end, the MLP model had better performance compared to ANFIS+FCM, MLP+SOFM, GRNN models.

SWAT is a continuous, physically based and distributed hydrologic model which all several hydrological processes like discharge, sediment yield nitrogen are simulated for each one of it. The purpose of this study is to test the efficiency of the Soil and Water Assessment Test (SWAT) and its applicability as a flow simulator, and using SWAT-Cup software and the SUFI2 algorithm as a means to calibrate and validate Neka Watershed in Mazandaran Province. Four indices were used to assess the goodness of calibration, viz., P-factor, R-factor, R2 and Nash-Sutcliffe (NS). Runoff data (1995-2004) of four hydrometery stations were used for calibration and (2005-2009) for validation of this watershed. The results of these values for flows at four stations for calibration process in Ablo, Pain zarandin, Karkhane siman and Sefid chah were 0.85, 0.78, 0.78, 0.89 for P-factor; 2.55, 2.03, 1.71, 2.43 for R-factor; 0.76, 0.62, 0.69, 0.71 for Nash-Sutcliffe and 0.71, 0.82, 0.76, 0.63 for R2. The results of validation were 0.87, 0.88, 0.72, 0.72 for P-factor; 3.61, 2.24, 3.56, 1.78 for R-factor; 0.74, 0.66, 0.58, 0.64 for Nash-Sutcliffe (NS) and 0.81, 0.68, 0.73, 0.61 for R2 respectively. In general, the results showed that SWAT could be a proper tool for simulating the flow rate values of the Neka Watershed.

Urban watersheds have been a centerpiece among communities over the last few decades. Every growing urban watershed requires a system designed to store rainwater (runoff). Hence, estimating the amount of runoff and runoff generation percentage of different parts in an urban catchment system is substantial. Therefore, this was set as the cornerstone for assessing the hydrological response of different homogenous units of our study area. To this aim, land use maps were prepared for three different years (i.e. 1996, 2006, and 2016) using available archived data, census blocks obtained from National Cartographic Center, and satellite images in ArcGIS platform. Afterwards, the impact of land use changes on the peak discharge was analyzed over these years using ASSA (CivilStorm) software. The results revealed that the peak discharge in 2016 is significantly higher than the years before which stems from the increasing pattern of impermeable surfaces, in such a way that a 26% increase in impermeable surfaces from 1996 to 2016 has consequently increased the discharge by 24%.

Fast and accurate estimation in Peak flow is one of the major issues in water resources management that have basic role in the design of hydraulic structures and biological activities in drainage basins. So that a proper assessment has a basic role in the success of administrative tasks. In this paper, using artificial intelligence methods (Multi-layer Perceptron Neural Network and the mixture of Multi-layer Perceptron Neural Network with genetic algorithm) to estimate yalfan river, s peak discharge in Yalfan,s sediment and hydrometer local gaging station. For these two models, 8 variables have been considered as the inputs that includes rainfall related to day of peak flow,5 days rainfall that occurs before of the flooding day, curve number of the basin(CN) and base discharge and finally peak discharge is considered as the output. With artificial intelligence after preprocessing of the data, the optimal structure of the model is determined with input and output data by evaluation criteria and trial and error. In the final, with the mixture of artificial network and genetic algorithm model, the optimum neural network model was determined which results were an input to genetic algorithm model, this has been a good performance in runoff forecasting in Yalfan Basin.

One of the most important consequences of soil erosion is sedimentation. The detection and surveying the type and amount of sediment is important because of its effects on irrigation networks, environment, and reservoirs. This study was performed in order to investigate the suspended sediment changes under the influence of rainfall erosivity cycle in Sorkhab- Keshvar watershed in the Lorestan province. For estimating the suspended sediment, we used a combination of sediment rating curve of mean loads within discharge classes and average daily discharge data. Monthly and semi-monthly EI30-based erosivity indices were calculated in 13 rain gauging stations inside and around of the watershead. In the next stage, erosivity maps based on kriging interpolation were produced in order to calculate the average monthly and semi-monthly rain erosivities. After calculating monthly and semi-monthly sediment loads, their correlations with corresponding erosivities were investigated. The results show that the maximum and minimum of suspended sediment occured in Azar and Shahrivar (Iranian month equal to Nov. 22 to Dec. 21 and Agu. 23 to Sep. 22) with the values of 246216 and 1272 ton, respectively. Also, the maximum and minimum of rainfall erosivity occured in Dey (Iranian month equal to Dec. 22 to Jan. 20) and summer respectively with the values of 182 and 0.01 MJmm ha-1 h-1.The highest values of semi-monthly erosivity and sediment observed in second half of Dey and Azar (Iranian month equal to Dec. 22 to Jan. 20 and Nov. 22 to Dec. 21) with the values of 104 MJmm ha-1 h-1 and 148241 ton, respectively.Sediment and erosivity showed two peaks in the watershed, two peaks of sediment occured in Azar and Farvardin (Iranian month equal to Nov. 22 to Dec. 21 and Mar.21 to Apr. 20) and for the reosivity occurred in Dey and Farvardin (Iranian month equal to Dec. 22 to Jan. 20 and Mar.21 to Apr. 20).

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 model for estimating flood discharge.

The behavior of suspended sediment during flood events is not only a function of energy conditions، i. e. sediment is stored at low flow and transported under high flow conditions، but also is related to the variations in sediment supply and sediment depletion. These changes in sediment availability result in so-called hysteresis effects. Therefore، Hysteresis pattern analysis is of great importance in sediment studies in the watersheds. However، their analyses has been rarely considered. In this study، based on the discharge and sediment concentration data collected from 8 storm events occurred during March 2 011 to April 2012، event suspended sediment dynamics of 7 tributaries of the Lake Zarivar watershed was investigated using hysteresis patterns. Based on the fact that all sampling points were not active in all events، about 46 hysteresis patterns were obtained. The analysis of results showed that 16، 13، 11، and 6 events had clockwise، irregular، complex and counterclockwise patterns، respectively. Small tributaries of the Zarivar lake watershed showed the rapid responses to the variation of storm intensity and the most hydrographs of different storms were multi peak discharges and consequently high suspended sediment variations led to different hysteresis patterns. The diversity of patterns suggested that the detailed processes of sediment transport were not only complicated during one event but also varied from event to event. The reasonable and statistically significant relationship (p<0. 05) between suspended sediment yield and peak discharge of each sampling point indicated that the data from all events may be statistically well described by a simple regression equation، regardless of different inter and intra-storm variations of the suspended sediment.

A check dam is a small dam with a simple and low cost structure and because of its specific material and simple building technology, it has a wide range of applications in flood control projects. In this research, the effects of check dams on reducing the flood peak and increasing the time of flood flow to reach to peak were investigated for Kan basin in north-west of Tehran. The hydraulic and hydrologic situation of the Kan basin was modeled using HEC-HMS software. Using hydrologic modeling the effect of building check dams on flood characteristics was studied in three scenarios of river slope change. The results showed that check dams reduced the flood peak to reduce between 0 and 0.9% in the first scenario (0.5 of the natural slope) and from 0.4% to 3.5% and 3.9% to 10.6% in the second (0.1 of the natural slope) and third (0.01 of the natural slope) scenarios, respectively. The time to peak also increased from 10 to 50 minutes. In hydraulic-hydrologic modeling, the effect of constructing check dams with no sediment in their reservoir was investigated for rainfalls of different return periods. The results revealed that with increase in rainfall return period, the effect of check dams on reducing flood characteristics will decrease. For instance, in the case of 100 check dams, the percentage reduction in peak outflow will decrease from 22.8 to 1.2 % for rainfalls of 2 and 20 years return period, respectively. In general, construction of check dams has no considerable influence on reducing constructive effects of floods. In other words, check dams should be used together with other structural and non-structural flood control methods.

Estimating instantaneous peak flow in watershed is one of the most important problems that cause hydrologists and experts to work seriously on it. One the new methods in river engineering and suspended sediment estimation is application of artificial neural networks which uses the same algorithm of human brain to find the internal relation between data based on the training process. The objective of this study is to compare the efficiency of artificial neural network method and experimental methods for estimating instantaneous peak flow in Fars province watershed. For this purpose، 24 years of daily peak and instantaneous peak flow of seven hydrometric stations were considered and tested for outlier data. Then the estimation was done based on experimental methods including Fuller، Sangal and Fill-Steiner and artificial neural network method and were compared based on RMSE، MAE and R2. Results showed that estimation of artificial neural networks is more accurate than experimental methods in all stations which indicated the lower errors of artificial neural network method compared with experimental methods.

It is necessary to use empirical models for estimating of instantaneous peak discharge because of deficit of gauging stations in the country. Hence, at present study, two models including Artificial Neural Networks and nonlinear multivariate regression were used to predict peak discharge in Taleghan watershed. Maximum daily mean discharge and corresponding daily rainfall, one day antecedent and five days antecedent rainfall, sum of five days antecedent rainfall and monthly mean temperature were extracted in Gatehdeh, Mehran, Alizan, Joestan and Gelinak hydrological units and entered into neural network model (from upstream to downstream, respectively). The feed forward network was used with one hidden layer and back-propagation algorithm. Then, the models were trained, validated and tested in three stages. The observed and estimated peak discharges of the models were compared based on RMSE and r. The results showed that neural network has better performance than nonlinear multivariate regression.

Complex in hydrological and hydraulic processes are one of the distinguishing features of urban areas. Therefore, accurate determination of the input variables of urban models and their impact on model output is time consuming and difficult. Sensitivity analysis shows which parameters impact more severely the results and ranked model parameters according to their effect on model output which can be calculated using this method. In this study the sensitivity of affective variables that influence urban flood peak, was studied by using the SWMM model in Imam Ali town in Mashhad city. The initial value of the eight-parameter including percentage of impervious area (%Imperv), slope, width, N-Manning for impervious area, N-Manning for pervious area, depth of depression storage on impervious area, depth of depression storage on pervious area and percent of impervious area with no depression storage reduction (%Zero-Imperv) and increases in the range of acceptable change and flood peak discharge was selected as the dependent variable. Result showed that with 30% increase in the amount of impervious areas, peak discharge increases 3.38 percent and this parameter was recognized as the most effective parameter and percent of impervious area with no depression storage has the minimum impact on peak discharge. It is recommended to increasing in the amount of impervious areas that causes from land use change, urbanization, no doctrinaire infrastructures causes increases in peak discharge and flood risk hazard in urban area.