Mohammad Hemmati; Davood Nikkami; Hassan Ahmadi; Gholamreza Zehtabian; Mohammad Jafari
Volume 1, Issue 1 , May 2009, , Pages 21-31
Abstract
Soil is one of the four elements of life and one of the most important agricultural and rangeland production factors. Soil erosion has impact on fertility of upstream lands and indirectly causes downstream damages. On a global scale, more than 50% of rangelands and about 80% of farmlands are significantly ...
Read More
Soil is one of the four elements of life and one of the most important agricultural and rangeland production factors. Soil erosion has impact on fertility of upstream lands and indirectly causes downstream damages. On a global scale, more than 50% of rangelands and about 80% of farmlands are significantly suffering from soil erosion and sedimentation phenomenon. Despite of agricultural benefits of rainwater, its erosive energy in the primary stages, detaches soil particles and creates surface runoff which has the most severe impacts on soil erosion. The effective energy in this shape of erosion is called rainfall erosivity, which is rainfall erosion potential and depends on rainfall physical characteristics. Some different indices are developed for quantification of rainfall erosivity. Some indices emphasise on the amount of rainfall or rain intensity. Worldwide investigations show that applying a certain index, like EI60 in USLE equation has not sufficient credit and according to climatic condition the best rainfall erosivity index should be determined. In this research, after establishing 21 erosion plots in Kaboudeh Oliya village, Kermanshah city, on two land use types of dry farming of 6, 12, 16 and 17 percent slopes and rangelands on 25, 35 and 45 percent slopes with three repetitions, 15 rainfall events which produced surface runoff were monitored by a recording rain gauge and the amount of surface runoff and sediment were measured. According to the literature, 45 rainfall erosivity indices were chosen to be compared. For facilitating and increasing accuracy of calculations on rainfall erosivity indices, a computer program was developed to analyze and extract necessary factors from each storm. The result showed that in the study area, EI60 is the best rainfall erosivity index and has maximum correlation coefficient of 0.721 with soil loss.
Ali Reza Eslami; Abdol Rasoul Telvari
Abstract
The hydrologic events and physical structure of a basin is related to governing climatic conditions. Basins have different hydrologic responses considering their various morphologic and climatic characteristics. It is recommended to separate basins with respect to their major factors into homogenous ...
Read More
The hydrologic events and physical structure of a basin is related to governing climatic conditions. Basins have different hydrologic responses considering their various morphologic and climatic characteristics. It is recommended to separate basins with respect to their major factors into homogenous groups with the same hydrologic conditions. This grouping is effective so that models for estimating flood peak discharge in each homogenous group have higher performance than a single model for all basins. In this research, firstly different morphological characteristic of selected basins were derived using GIS. Based on factor analysis, major variables (factors) including; basin area, weighted-average slope, drainage density and annual mean precipitation were selected. Then, all basins were classified in homogenous groups with respect to major factors using cluster analysis and discriminate functions analysis, statistical methods, and Andrew’s curve as a graphical method. To investigate on the efficiency of grouping, two control basins were selected and their similarity to each homogenous group was carried out using above methods. By applying regression models developed for whole region and homogenous groups, flood peak discharges for two basins with different return periods were estimated. Simulated values compared with observed data and showed that models for homogenous groups have better performance than those for the whole region.
Mahmood Arabkhedri; Kolsoum Sedarati; Abazar Esmali
Abstract
Based on expert estimates, many Iranians believe that the amount of sediment yield is annually increasing. This study has attempted to assess the temporal trend in Suspended Sediment (SS) of Jajroud and Karaj rivers at Roudak and Sira stations. respectively with adequate data collected during four decades. ...
Read More
Based on expert estimates, many Iranians believe that the amount of sediment yield is annually increasing. This study has attempted to assess the temporal trend in Suspended Sediment (SS) of Jajroud and Karaj rivers at Roudak and Sira stations. respectively with adequate data collected during four decades. The SS yield data and SS concentration as well as flow rate data were analyzed. Preliminary investigation showed that more than 92 percent of the SS at Roodak and Sira stations is transferred by top two and three flow deciles (equal to 20 and 30 percent) of the effective or flood discharges. Among these, the highest decile (10 percent) is responsible for carrying about 80 and 64 percent of SS accounted for the two study sites correspondingly. Therefore, mainly analyzing the highest decile flow data was considered. Four techniques were performed including: a) fitting regression lines to the measured SS concentrations and weights vs. time, and b) graphical comparisons of dependent variables (average discharge, average SS concentration and weight) during the four decades, c) using the Kruskal–Wallis test, and d) using Kendall rank correlation coefficient. All interpretation techniques showed decreasing trends vs. time which were significant based on the two nonparametric techniques. Since, the highest decile of daily flows of study sites have not shown any increasing trends during study period, it can be concluded that unlike the general publics’ believes the amount of SS has decreased. A possible explanation for this descending trend might be as a result of 43 and 25 conservation projects implemented during recent 30 years in the upstream basins of Amirkabir and Latian dams, respectively. The descending SS trend does not necessarily mean lower rates of erosion in these basins; but it rather means lesser sediment delivery ratios.
Morteza Miri; Mohammadreza Kousari; Mehran Zand
Abstract
One of the most common and effective problems in long-term climate studies is the presence of gaps in the time series of various climatic and hydrological data. Therefore, the present study evaluates the accuracy of methods for infilling missing data of daily, monthly and annual temperature time series ...
Read More
One of the most common and effective problems in long-term climate studies is the presence of gaps in the time series of various climatic and hydrological data. Therefore, the present study evaluates the accuracy of methods for infilling missing data of daily, monthly and annual temperature time series in the arid regions of Iran. For this purpose, the observed daily minimum, average and maximum temperature data for the period 1987-2014 measured at 73 synoptic stations distributed all over arid regions of Iran were used. Methods of readjustment used include: Normal ratio method, linear regression, multivariate regression and Inverse Distance Weighting (IDW). In this study, the capability of each mentioned methods for infilling missing data of daily, monthly and annual precipitation time series in the arid regions of the Iran was investigated, while the proportion of missing data varies from 5 to 50% of total data. In order to compare and evaluate the accuracy of the four mentioned methods three statistical indicators, namely the correlation coefficient (R), the Root Mean Square Error (RMSE) and Nash coefficient were used. The results showed that in general, each of the methods mentioned had different functionalities at a special level of readjustment and time scale. On annual and monthly scales, linear regression and normal ratio methods are the most accurate method in readjustment temperature data in the arid region of Iran. The correlation value between the readjustment and observational data at different levels reaches more than 0.95 using these methods. On the daily scale, there is no significant difference between the accuracy of the methods used in the readjustment of temperature data, and almost all four of these methods have appropriate accuracy because in all methods the correlation between readjustment and observed data is more than 90%. However, multivariate regression methods with an average correlation of 0.99 showed the most accurate performance in readjustment daily data at different levels of readjustment. Generally, each method should be used in accordance with the conditions, and therefore it is recommended to develop a software package for infilling missing data.
Ali Ahani; Seyed Saeed Mousavi Nadoshani
Mehran Zand; Morteza Miri; Mohammadreza Kousari
Abstract
Climate change can lead to changes in the frequency, intensity, and duration of extreme climate events in different parts of the world. The purpose of this research is to investigate temperature and precipitation extremes in Lorestan Province. The data used in this study included precipitation and the ...
Read More
Climate change can lead to changes in the frequency, intensity, and duration of extreme climate events in different parts of the world. The purpose of this research is to investigate temperature and precipitation extremes in Lorestan Province. The data used in this study included precipitation and the maximum and minimum daily temperature of nine synoptic stations in Lorestan Province during a 28-year (1990-2017) common period. The matrices of minimum and maximum temperatures and precipitation daily data for each station were prepared and used to compute the extreme climate indices (26 precipitation and temperature extreme indices based on the recommendation of CLIVAR \ CLL expert group) using the R programming software. The results of studying the trend of cold and hot extreme weather indicators during the period 1990-2017 in the province using the Mann-Kendall trend test showed that for all stations, the hot indices have increased and more cold indices have decreased. In different regions of the province, positive and negative trends of hot and cold indices with different intensities have occurred. The highest upward trend of the warm extreme indices has occurred for the hot night’s index. Among the cold indicators, the greatest decrease occurred for several frost days and cold days indices. The decreasing trend of ice days is significant for 45% of stations at 99% level and the decreasing trend of cold days for 77% of stations at different levels of 90, 95, and 99%. The results of the study of the frequency of occurrence and trend of precipitation extreme indicators in Lorestan province showed that the total rainfall of this province, like many regions of the country, has decreased. In contrast, the occurrence of maximum rainfall in addition to being significant in the province has an increasing trend during the period 2017-1990. These conditions can indicate an increase in the number of occurrences of heavy and short-term rainfall events and, shorten the period of the rainfall season in the region.
Pari Saeidi; Seyed Hamidreza Sadeghi; Abdulrasul Telvari
Abstract
Sediment graph is an important tool for soil and water resources management of watersheds. It is therefore important to find an appropriate procedure to simulate sediment graph data in different watersheds with inadequate and unreliable suspended sediment data. However, achieving simple procedures based ...
Read More
Sediment graph is an important tool for soil and water resources management of watersheds. It is therefore important to find an appropriate procedure to simulate sediment graph data in different watersheds with inadequate and unreliable suspended sediment data. However, achieving simple procedures based on easily accessible data has been less considered. Hence, the present study was conducted in Galazchai Watershed in West-Azerbaijan Province, Iran, with an area of some 103 km2 to investigate the ability of synthetic sediment graph development by using hydrograph. Towards this attempt, a databank of 18 storm events occurred during autumn 2011 and spring 2014 was developed and corresponding total and direct hydrographs and sediment graphs were prepared. All total and direct sediment graph components were simulated using corresponding hydrograph components with the help of different bivariate regression models and the best performed model was ultimately determined by applying different criteria. The results showed that the simulation of different total sediment graph components was possible using hydrograph components except for base time and ordinates of 50 and 75 percent of peak. Direct sediment graph simulation results also verified the simulation ability of all components except for ordinates of 75 percent of peak. According to the results, simulation of temporal components with the lower relative errors had better performance than the other components. So that, for total sediment graph, the lowest relative estimation and validation errors for time to peak were 48.86% and 45.65%, respectively. Also, the best performed model developed for the direct sediment graph base time had the lowest relative estimation and validation errors of 23.03% and 21.75% and the highest coefficient of efficiency of 0.93.
Aiding Kornejady; Hamid Reza Pourghasemi
Abstract
The current study is aimed to map landslide susceptibility in the Chehel-Chai Basin is located in the Golestan Province. To this end, two data mining models namely support vector machine and boosted regression tree were employed due to their robust computational algorithm. Landslide inventories were ...
Read More
The current study is aimed to map landslide susceptibility in the Chehel-Chai Basin is located in the Golestan Province. To this end, two data mining models namely support vector machine and boosted regression tree were employed due to their robust computational algorithm. Landslide inventories were recorded through several field surveys using global positioning system (GPS), local information and available organizational resources and corresponding map was created in the geographic information system (GIS). Reviewing several worldwide studies, 12 predisposing factors including proximity to fault, proximity to stream, proximity to road, lithological units, soil texture, land use/ cover, slope degree, slope aspect, altitude, plan curvature, profile curvature and topographic wetness index (TWI) were chosen and the corresponding maps were produced in the geographic information system. In order to evaluate models’ results the receiver characteristic curve (ROC) and 30% of landslide inventories were used. Results showed that the SVM model with the AUC value of 0.82 had better performance on landslide susceptibility zonation over the study area and followed by the BRT model with the value of 0.77. Based on the SVM model results, about 45% of the Chehel-Chai Basin has high and very high landslide prone areas.
Shahriar Sobh Zahedi; Ramin Naghdi; Mohammad Reza Gharibreza; Ali Salehi; Ghavamoddin Zahedi Amiri
Abstract
The method employed in this study was based on experimental research and field study. In this method, the stored radiocesium of the forest region which was supposed to be converted into Poplar plantation has been compared with the stored radiocesium of the reference region. 11 core samples were taken ...
Read More
The method employed in this study was based on experimental research and field study. In this method, the stored radiocesium of the forest region which was supposed to be converted into Poplar plantation has been compared with the stored radiocesium of the reference region. 11 core samples were taken from reference region and then 7 core samples were selected from the transect which was a part of Poplar plantation that were taken by topographic characteristics in a depth of 25 centimeters, Having prepared the core samples according to the IAEA, they were packaged into the special Gama spectrometer containers. After that the amount of radiocesium of all samples has been measured by Bq kg-1 scale. The findings revealed that the amount of radiocesium in reference region was computed as 5894.1. Bq m-2 y-1. In the present study, soil loss rate during transect was estimated using proportional conversion models and mass balance I and II of 18.70, 22.72 and 18.64 ton / ha, respectively. These values were obtained for slope of 10-20%, canopy cover of 25% and clay loam soil under 1000 mm precipitation. This study recommended mass balance model II for estimation of erosion in changed land use areas and concluded that forest land use change to plantation due to reduction of long soil cover and plantation management by removing other seedlings and herbaceous cover increased the rate of soil erosion occurs. This process for many years has caused the erosion rate to exceed and has caused the loss of 0.1 cm of soil per year.
Rahim Kazemi; Jahangir Porhemmat
Abstract
Understanding the base flow can be useful in river flow analysis, rainfall-runoff modeling, calibration of models, water resource management in low flow conditions and determination of the amount of water storage in watershed. In this research, 22 stations were selected with the appropriate data and ...
Read More
Understanding the base flow can be useful in river flow analysis, rainfall-runoff modeling, calibration of models, water resource management in low flow conditions and determination of the amount of water storage in watershed. In this research, 22 stations were selected with the appropriate data and common period of the years of 1982-2012. The trend of flow changes during the months of the year was determined for all hydrometric stations in the study area and the driest month was determined. Then, the calibration of six recursive digital algorithms was performed using the long-term data of the driest month of the year and after obtaining optimal parameters of the models, the base flow separation for the whole period was performed. The performance evaluation of the models was done using root mean square error. The results showed that the major part of the river flow in the study area was related to the base flow and the minimum, maximum and average annual base flow index for the whole period was equal to 0.48, 0.62 and 0.56, respectively, representing more than 50% of ground water contribution to stream flow of the studied watersheds. Results of the evaluation of the models using the root mean square error showed that the mean error in the research area for all the methods ranged from 0.025 to 0.044. The minimum was related to Lynie and Holick, and the maximum related to the One-parameter digital filter. Over all, conclusion of the results of the calibration process and investing the correlation between calculated and measured data showed that there was a correlation with a coefficient of explanation of more than 80%. Calibration method with dry season data in the absence of tracer-based methods is suggested as the most suitable method for calibrating digital separation filters in the study area.
Jamshid Yarahmadi; Davood Nikkami; Ali Shahnavazi; Mohammad Ebrahim Sadeghzadeh
Abstract
Watershed residents' benefit increasing and soil erosion controlling are the main goals of agricultural sustainable development. Landuse optimization operation is an effective solution in order to maximizing the benefits, as well as minimizing soil erosion damages. Current research was executed in southern ...
Read More
Watershed residents' benefit increasing and soil erosion controlling are the main goals of agricultural sustainable development. Landuse optimization operation is an effective solution in order to maximizing the benefits, as well as minimizing soil erosion damages. Current research was executed in southern parts of Ahar Chaey Watershed in East Azerbijan Province. In this research, Multi-Objective linear programing based on Simplex method applied for optimizing landuse in form of three different scenarios: current landuses, implementation of management into current landuses and performance of the standard landuses by WinQSB software. Results showed that due to landuse optimization, irrigated orchards could be increased from 1.736 to 6.629 km2. In addition, based on suitable soils and adequate rainfalls, it is expected to expand the rainfed orchards up to 9.72 km2. Also, the weighted average of soil erosion reduces from 16.3 to 14.8 and from 10.11 to 9.5 tha-1year-1 within the first and second scenarios, respectively. This rate will reduce up to 6.8 tha-1year-1 in the standard landuse situation. On the other hand, maximizing results showed that the annual net benefits increases from 6.6 to 12.9 and 8.46 to 14 million Rails per unit area in the first and second scenarios, respectively. This rate increases up to 15.67 million Rails per unit area for standard landuse situation. Sensitivity analysis results showed that irrigated and rainfed orchards are of high sensitivity in maximizing profit functions due to high profitability of these landuse in unit area. In contrast, the rangelands, forests and drylands are of high sensitivity in soil erosion minimization, so that with increasing their area, soil erosion will increase significantly in the region.
Raouf Mostafazadeh; Amir Sadoddin; Abdolreza Bahremand; Vahedbordi Sheikh; Habib Nazarnejad
Volume 2, Issue 2 , July 2010, , Pages 83-93
Abstract
Assessment of flood control projects in the same conditions is essential in order to improve decision making that assist us in watershed management purposes. Focus of this study is on assessing hydrological effects of the Jafar-Abad watershed management project. The study area (109 km2) located in north ...
Read More
Assessment of flood control projects in the same conditions is essential in order to improve decision making that assist us in watershed management purposes. Focus of this study is on assessing hydrological effects of the Jafar-Abad watershed management project. The study area (109 km2) located in north of Iran in the Golestan province. Paired t-tests were performed for Indicators of Hydrologic Alteration (IHA) in Taghi-Abad gauging station, located in the outlet of the catchment, before and after construction of 58 check dams. HEC-HMS model was calibrated using 12 storm events and validated for study area. Calibrated HEC-HMS model was applied to rainfall-runoff modeling in sub-catchments and Level-pool method used for reservoir elements. Design flood hydrographs for 2-100 year return periods were simulated for both before and after check dams construction periods. The results of statistical analysis indicate that existing flood control measures had no significant impact on the hydrologic characteristics measured by IHA in 95% confidence level. The results indicated that constructed structures do not have important effect on IHAs and the amount of these effects was less than 1.5 percent in all cases. Also, by increasing in return period, the effects of structures on peak discharge and flood volume were reduced.
Seyed Ahmad Hosseini; Nasrolah Javaheri; Mehdi Habibi
Abstract
This study investigated the status of sediment transport and deposition in Khar-rud River, Qazvin province, Iran. The aim was to determine the possibility of construction of sand and gravel mining workshops in the margin of Khar-rud Flood-plain. Here with calculating sediment transport rate and specifying ...
Read More
This study investigated the status of sediment transport and deposition in Khar-rud River, Qazvin province, Iran. The aim was to determine the possibility of construction of sand and gravel mining workshops in the margin of Khar-rud Flood-plain. Here with calculating sediment transport rate and specifying the distribution of sediment deposits in various parts of the river, an applied program for sand harvesting from the river bed, is developed. In this project, after preparing the basic information, such as information about river geometrical shape, roughness coefficients of different sections, information related to size gradation of suspended sediments and bed material, river hydrology data and boundary conditions of downstream hydraulic system, using HEC-RAS model, sediment loads and its distribution along the river was simulated. Simulation was done based on classified data from daily flow discharges during a 37-year period. After calibrating the HEC-RAS model and selecting Yang sediment transport equation as the closest relationship to the sedimentary data measured by regional Hydrometric stations, the average volume of sediment yield from the river was estimated 1.75 million tons per year. Finally, considering the changes in the river bed elevation for each cross-section, the amount of sediment passing during simulated 37-year was calculated. Using the results of the model and sedimentation changes along the study reaches, the volume of sediment transport in each river cross section, the river width and its private region and considering the maximum permissible depth of bed-material removal equal to 1 m, the most suitable mining length and period in the different reaches of river was determined, discussed and showed in ARC-GIS environment. Based on simulation results, the average depth of sand which can be taken safely from the river-bed was estimated to be 40cm and the most suitable period of time for sand mining along the river was recommended from January to May. It was determined that HEC_RAS hydraulic model, covers about %63 of initial engineering judgments for the amount and location of sand mining.
Rahim Kazemi; Ali Reza Eslami
Abstract
Base flow and related index is influenced by morphometric, geologic and hydroclimatological factors. As a result, it is precondition data for planning and water resources management. In this research, base flow and related index were extracted from daily stream flow data using one parameter recursive ...
Read More
Base flow and related index is influenced by morphometric, geologic and hydroclimatological factors. As a result, it is precondition data for planning and water resources management. In this research, base flow and related index were extracted from daily stream flow data using one parameter recursive digital filter in eighteen hydrometric stations of the Caspian Basin. Physiographic, climatic, hydrological, and geological factors were calculated in GIS environment. Using factor analysis of the eighteen parameters, five factors were selected as independent factors. Statistical models were formulated to calculate several regressions between hydroclimatological and physiographic parameters. Further, residual analysis method was used to compare and evaluate the accuracy and efficiency of the models. Results showed that Hard Formations, the average height of basin, drainage density, and coverage of forest were the best predictors of the base flow index. Statistical models highlights importance of Q90/Q50 ratio as the suitable hydrologic index to estimate the base flow index. Besides, this model confirmed controlling role of Hard formations and the forest coverage on the base flow index.
Abdolali Adelpour; Majid Soufi
Abstract
Erosion and sedimentation study and design of the distance between spreading channels are basic requirement in flood water spreading projects. Different environmental parameters including topography and slope, soil texture, vegetation cover and flow resistance affect the hydraulic characteristics of ...
Read More
Erosion and sedimentation study and design of the distance between spreading channels are basic requirement in flood water spreading projects. Different environmental parameters including topography and slope, soil texture, vegetation cover and flow resistance affect the hydraulic characteristics of the flood water spreading area. So it isnecessary to investigate the effect of environmental parameters according to natural conditions and simulation of overland flow. This study was done in the Gareh Bygone plain, in the south of Fasa city. An open hydraulic flume with 120 m length, 0.4 m width and 0.25 depth was used to simulate concentrated overland flow with 0.1 mdepth. Three experiments were examined and for each experiment, discharge flow and mean flow depth were measured directly and other parameters such as mean velocity and shear stress were calculated. Erosion or sedimentation depths were calculated by comparing flume bed elevations in the cross sections with one meter intervals. Results of this study show that erosion and sedimentation phenomena were changed with theincrease or the decrease in trends of shear stress along the flume and shear stress parameter were also changed with bed slope and roughness coefficient and became maximum at 75 m from the top end of the flume. On the other hand, according to the bed elevations of cross sections in two steps maximum erosion depth occurred at 75 mfrom the start of the flume which was confirmed with maximum shear stress. So, we can conclude that channel erosion threshold was established in 75 m from the top end of the flume and it can be considered as channel spreading distance.
Hossein Saadati; Shaban Ali Gholami; Foroud Sharifi
Volume 1, Issue 2 , July 2009, , Pages 87-98
Abstract
Lack of hydrometric data is the main issue for research and executive plans. In the present study in order to solve this issue, the capability of SWAT model has been studied in terms of daily discharge simulation in un-gauged watersheds. This model can simulate six hydrological and biological processes ...
Read More
Lack of hydrometric data is the main issue for research and executive plans. In the present study in order to solve this issue, the capability of SWAT model has been studied in terms of daily discharge simulation in un-gauged watersheds. This model can simulate six hydrological and biological processes such as daily discharge, daily sediment, yearly and monthly water balance, water quality, agricultural products and estimation of vegetative cover for different animal grazing management systems. Simulation has been done for both gauged and un-gauged basins in Kasilian catchment for two time periods as calibration and validation of model. Calibration has been done using data derived from 4 years recording data (1987-1981) while validation has been done using 6 years data (1981-1986). Results show that, ABF, CN2 and REVAPC parameters are most sensitive and also Z and T-Laps parameters are low sensitive among other parameters. The model simulated runoff reasonable with r2=0.69, PBIAS=-2.5, and NS=0.72, whereas, the validation of model for the same data showed that r2=0.57, PBIAS=4.3, and NS=-0.54, which indicates that the performance this model is not quite valid for low stream flows because of sensitivity of hydrological parameters. The new version of SWAT model, modified during 2000 to 2005, has a capability in using GIS, thus it can be used in the same study area.
Seyed Aliasghar Hashemi; Sargis Ghazariyan
Abstract
In this research, two small sub-basins were selected in Darjazin Watershed of Semnan to evaluate the effect of ruck check dams on peak and volume of flood in small watersheds. Two watersheds were chosen as study area in a part of southern Alborz Mountain with arid and semi-arid climate. These watersheds ...
Read More
In this research, two small sub-basins were selected in Darjazin Watershed of Semnan to evaluate the effect of ruck check dams on peak and volume of flood in small watersheds. Two watersheds were chosen as study area in a part of southern Alborz Mountain with arid and semi-arid climate. These watersheds are located in upland of Mahdishahr city and many check dams are constructed for flood control in past few years. All check dams were examined during field operation and their sedimentation were assessed. Results showed that all check dam reservoirs were filled by sediment. In this research, the peak and volume of floods were assessed in three scenarios of 1) watersheds with no check dams 2) watersheds with empty of sediment check dam reservoirs and 3) watersheds with full of sediment check dam reservoirs. HEC-HMS model was used for rainfall-runoff simulation. . Mean comparison test by paired method for all three scenarios showed that flood peak and volume have significant difference at α=1% level. But, flood peak and volume in scenario 2 are computed less than that of scenario 1 and in scenario 3 are computed more than that of scenario 2. On the other hand, flood peak and volume in the scenario 3 slightly decreased by 4.8 and 5.7 percent respectively compared to scenario 1 where is not significant based on the objectives of project.
Mehdi Bashari; Seyed Hamid Reza Sadeghi; Abdolsaleh Rangavar
Abstract
Investigation of effective factors on soil erosion and their variability analysis is essential for soil and water conservation projects. The present research was carried out to survey the role of two north and south facing slope plots on soil erosion on storm basis at Sanganeh watershed located in Khorasan ...
Read More
Investigation of effective factors on soil erosion and their variability analysis is essential for soil and water conservation projects. The present research was carried out to survey the role of two north and south facing slope plots on soil erosion on storm basis at Sanganeh watershed located in Khorasan Razavi province, Iran. The study was conducted using a pair of small plots with dimensions of 2×2 meters. The plots were be designed using metal sheets and their outlet was directed towards collecting tanks. These plots were established close to each other at two different aspects. The generated runoff and sediment from plots caused by 12 storm events during October 2006 and May 2007 were collected and sediment concentration was ultimately calculated. The results of sediment concentration analysis verified a significant difference (p<0.01) between soil erosion study plots with very low quantities in plots installed in northern aspect. The difference was clearly associated with effect of slope aspects on vegetation cover.
Jalal Barkhordari; Davood Nikkami; Mohammadbagher Samadi; Monirosadat Tabatabaeizadeh
Abstract
Rainfall erosivity is one of the most important factors in determining soil erosion. This factor is usually expressed as erosion indices that are based on rainfall characteristics. In this study, after construction of 12 runoff-sediment plots in Nir Research Station in Yazd province, the amount of runoff ...
Read More
Rainfall erosivity is one of the most important factors in determining soil erosion. This factor is usually expressed as erosion indices that are based on rainfall characteristics. In this study, after construction of 12 runoff-sediment plots in Nir Research Station in Yazd province, the amount of runoff and sediment from each plot were monitored and measured for 12 rainfall events. Then, based on a world wide literature review, 61 rainfall erosivity indices were identified. The rainfall erosivity indices were determined for each of the storms with extracting the required parameters. In order to determining suitable rainfall erosivity indices, the correlation between the rainfall erosivity indices and soil loss values were determined. The results showed that PI602, PI302, RPI602, RPI302, RI60 with 0.730, 0.713, 0.703, 0.694 and 0.664 percent had highest correlation with soil loss amount. Generally, in the climatic condition of study area, the indices based on rainfall intensity with total amount of rainfall multiply in the square of 60 and 30 minutes rainfall are better than other indices.
Seid Saeid Ghiasi; Faezeh Rajabzadeh; Somayye Najirda; Sadat Feiznia; Aliakbar Nazari Samani
Abstract
Shallow landslide susceptibility assessment by using appropriate methods and determine of effective factors in reduce of its hazards is so effective. The aim of this study is to determine the effective factors on shallow landslide occurrence and investigation of Statistical Index Method (SIM) efficiency ...
Read More
Shallow landslide susceptibility assessment by using appropriate methods and determine of effective factors in reduce of its hazards is so effective. The aim of this study is to determine the effective factors on shallow landslide occurrence and investigation of Statistical Index Method (SIM) efficiency for landslide susceptibility mapping. So, determination of each class of factors’ weights was accomplished by using SIM. That was done by adoption of inventory landslide map and ten initial factors including: slope, aspect, rainfall, altitude, drainage density, plan curvature, land use, geology, geomorphological faces and rock unit sensitivity to erosion in ArcGIS 9.3. Then model efficiency was evaluated by using percentage of area under ROC curve and the results showed high accuracy (0.95) of SIM. Principal Component Analysis (PCA) was used for determination of primary causative factors of shallow landslide occurrence. Results showed that five variables of rainfall, slope, aspect, rock unit sensitivity to erosion and plain curvature are the most effective factors on landslide occurrence, respectively.
Seyed Hamid Reza Sadeghi; Gholam Reza Shojaee; Hamid Reza Moradi
Volume 2, Issue 3 , October 2010, , Pages 143-149
Abstract
The intensity and type of soil erosion are functions of climatic, topographic, soil and land use characteristics. The role of land use is more than others due to the human impacts. In order to study the relationship between land use change and soil erosion, the Manderijan watershed located upstream of ...
Read More
The intensity and type of soil erosion are functions of climatic, topographic, soil and land use characteristics. The role of land use is more than others due to the human impacts. In order to study the relationship between land use change and soil erosion, the Manderijan watershed located upstream of Zayandehrud dam basin, comprises 23000 ha, was selected. The satellite images of MSS1979, TM1990, TM1998 and ETM2002 were used to map land use as well as soil erosion features during the study periods. The relationship between the existence as well as areas of each particular soil erosion feature and land use was also investigated using regression and Chi-square analyses. The results of the study verified a significant relationship between areas of land uses and soil erosion features. The moderate sheet erosion was further related to the land use changes in particular in the form of cubic regression equation having the determination coefficient of less than 81% and relative error of below 39.65%. The Chi-square analysis was also certified the insignificant relationship between existence of each particular soil erosion feature and land use whereas the relationship between land use and soil erosion areas could be significantly approved. The results of the study therefore can be utilized for proper management of the area through devoting necessary attention into the land uses.
Jamal mosaffaie; Majid Ownegh
Abstract
Landslide is one of the natural hazards that makes numerous financial and life damages each year. By landslide hazard zonation, we able to detect susceptible areas to landslide and with applying developed methods and suitable management the abundance of land sliding and the amount of damages will be ...
Read More
Landslide is one of the natural hazards that makes numerous financial and life damages each year. By landslide hazard zonation, we able to detect susceptible areas to landslide and with applying developed methods and suitable management the abundance of land sliding and the amount of damages will be reduced. In this study potential landslide hazard evaluated using multivariate regression model at a part of Alamout watershed in general level (1:50000 scale). So first, landslide distribution map of area prepared using study of air photos and field surveying. After reviewing available resources along with reviewing the benefit of experts, all factors that can affect landslide were extracted and among them eight parameters including (lithology, slope percent, aspect, height, distance to fault, land use, rainfall and earthquake acceleration) were selected as landslide effective factors. AHP and pair comparing technique were used for numerical weighting to qualitative categories of land use, aspect, and lithology parameters. Homogeneous units map prepared using overlaying 8 maps of landslide key factors, and by crossing of homogeneous map and landslide distribution map. Categories of each parameter were detected in each landslide, and with weighting average of them, the effect of each parameter was determined in each landslide. Therefore 84 observations prepared for statistical analysis of landslides. Results showed that 5 parameters including lithology, slope, height, distance to fault and land use have meaningful relation with landslides that determining coefficient between these parameters as independent variables and logarithm of landslides area as dependent variable was 60.7%. Landslide hazard zonation map and landslide distribution map were crossed and efficiency of model was evaluated. The Chi square test was used for comparing of difference between hazard classes of model. Results show that model has higher efficiency in higher classes of hazard. Results show also measured chi square rate is meaningful at 99% of confidence interval, and there is suitable separation among landslide hazard classes.
Hamidreza Peyrowan; Ali Jafari Ardekani; Mohsen Shariat Jafari
Abstract
This research has been done for the study of morphology of Ghezel Ouzan River from Ostoor to Manjil dams in two gorge and floodplain basins at 37 years period based on aerial photos, topographic maps and field surveying. The results showed the mean sinuosity ratios of, 1.46 and 1.22 for gorges and floodplain ...
Read More
This research has been done for the study of morphology of Ghezel Ouzan River from Ostoor to Manjil dams in two gorge and floodplain basins at 37 years period based on aerial photos, topographic maps and field surveying. The results showed the mean sinuosity ratios of, 1.46 and 1.22 for gorges and floodplain basins so that they can be classified as meandering and sinuous river reaches respectively. More sinuosity at gorge basin is due to the geological and tectonically factors. In the other words, the river plan initiate and mature based on rock canal that originated from above mentioned geological factors. At floodplain basin in Pavehrood to manjil dam with 60 km length river reach, the river showed three obvious sinuous canaliform, sinuous point bar, sinuous braided and braided and anastomising plan . At period 37 years braiding extend in the boundary about 1.2 km widths in Hezarrood area. If the rate of widening of the river in this basin presumes in uniform rate, the velocity of the river widening is about 32 meters per year that is noticeable. Bank erosion with meandering form of the river in Haroonabad area through meandering growth and extensions of the loops occurred up to 850 meters at the mentioned periods. Based on central angel of meanders loops, 57.72 percents of loops are extended modes, 25.93 % very extended, 16.05 of others are new so the river has meandering hazard. Extension mode of the loop growth is the main mode with 56% frequency and based on water shear stress distribution, geometry of loops and relative radius of the loops, consequently accumulation point of the shear stress, the modes of translations, rotation, compounding and chute and neck cut off are observed. More than 75 % of canal shifting cases of the river is toward left bank so that the construction of any structures on the left bank of the river would be dangerous.
Rahim Kazemi; Jahangir Porhemmat; Bagher Ghermez Cheshme
Abstract
Understanding the interaction of drought phenomenon and hydrological response of catchments can lead to obtaining some information for optimal water resource management. The aim of this study was to investigate the temporal relationship between drought and groundwater contribution to stream flow, in ...
Read More
Understanding the interaction of drought phenomenon and hydrological response of catchments can lead to obtaining some information for optimal water resource management. The aim of this study was to investigate the temporal relationship between drought and groundwater contribution to stream flow, in Kaka–Reza Sub-catchment. In this study, the common period of 1382-2017 was considered for the corresponding hydrometric and rain gauge stations. The Standardized Precipitation Index (SPI) was then calculated at time scales of three, six, nine, 12, 18 and 24 months. Base flow and related index were calculated by B-Flow-Line and Halick digital filter method in monthly, annual and total time bases. Then the Standardized Base Flow Index (SBFI), the Base Flow Duration Curve (BFDC) and the base flow duration curve shape index (SBFDC) was calculated. Changes in BFDC and the corresponding shape index and the relationships between SPI and SBFI were investigated and analyzed using the correlation method. The results showed that the average Base Flow Index during the research period was equal to 0.52 and its minimum and maximum were equal to 0.46 and 0.57, respectively. Also, the trend of bas flow changes is a decreasing trend with a low slope. The trend of changes SBFDC decreases over study period with a low slope. The rate of slope change is also from one to three percent, and close to the straight line, which indicates the tendency for base flow to be stable in the long time. The greatest impact of the drought phenomenon on the river base flow is in the time step of nine and twelve months. The correlation between SPI and SBFI with a coefficient of determination 0.87 confirms the increase in the groundwater contribution to base flow, with a delay of nine to twelve months.
Mohsen Tavakoli; Haji Karimi; Hadi Norollahi
Abstract
Climate change and global warming is one of the most important issues in the world that is discussed in public and professional meetings. Long term climate change forecasting has an important role on water resources planning and management, due to fragile climate of our country. The present study aimed ...
Read More
Climate change and global warming is one of the most important issues in the world that is discussed in public and professional meetings. Long term climate change forecasting has an important role on water resources planning and management, due to fragile climate of our country. The present study aimed to investigate the effects of climate change on discharge changes in Golgol Watershed as one of the Ilam dam sub-watersheds. In this research, first, temperature, precipitation and potential evapotranspiration data were downscaled and then, hydrological condition of the watershed is simulated using SWAT hydrological model. Next, the results of downscaled HadCM3 data under two scenarios of A2 and B2 were downscaled using SDSM and in the next step stream flow of three period including 2010-2039 (2020s), 2040-2069 (2050s), 2070-2099 (2080s) and base period of 1990-1961 (Baseline), simulated using SWAT model. Finally, the effects of climate change assessed until the end of the century. The results indicated that annual discharge will decrease for 2020s, 2050s and 2080s under A2 scenario by 6.3, 16.9 and 24.1percent, and will decrease under B2 scenario by 10.9, 8.8 and 13.2 percent, respectively. Resualts demonstrated that climate change as one of the negative phenomena that affects on the amount of water in Ilam Dam should be considered by managers and planners.
