IRANIAN JOURNAL OF WATERSHED MANAGEMENT SCIENCE AND ENGINEERING
Year:2016 | Volume:10 | Issue:34 |Papers Count:15

Flood is a hydrologic process whose dimensions change under different natural and artificial conditions of the earth surfaces as well as climatic conditions. Flood can be taken as a natural disaster and will bring about damages and casualties, if this phenomenon is not well recognized enough, or if it is not controlled or stopped. Appropriate planning can be taken into account to reduce the financial damages and civilian casualties caused by floods, by recognizing flood hazard and its spatial distribution. In this research, a method was suggested to determine flood hazards, based on main factors affecting hazard, and then applied for Hendijan-Jarrahi basin in the southwest of Iran. The results show that seven factors, including the intensity of flood potential, flood frequency, flood damage, flood casualties, the population exposed to the flood, residential places and lands exposed to the flood, were recognized as the main parameters to control flood hazard. Afterwards, the matric of hazard factors were identified by weighting to each of them and determining their domains based on data of floods during the last 50 years in second order basins of the country. Flooding areas also were recognized by using the Landsat TM+ 2002. In addition, the intensity of flooding potential were estimated with different return periods by applying the data of hydrometery stations and using regional analysis of daily and instantaneous peak flow for applying to ungaged basin. the layer of flood hazard were prepared based on 5 factors including flood frequency, flood damage, civilian casualties, the population and residential areas exposed to flooding. Then after, the flood hazard zoning were recognized and mapping, by combining and overlaying the layer of flood hazard with the layers of flooding areas and flooding intensity. By applying the model in Hendijan-Jarrahi basin, it was inferred that in this basin the maximum flooding took place in a fourth order Khairabad basin, following by Zohreh basin in Hendijan, otherwise, downstream Hendijan basin had the order of sever flood hazard. Moreover, Allah basin located in the upstream of Jarrahi had the maximum specific flood discharge yet the flood hazard in this basin was low risk. Also, the flood hazard is in the mean level of risk in Maroon and downstream of Jarrahi. Therefore, flood intensity and flood hazard do not much in one area, so it should be into account the basins which are flood prone to control the flood and reduce the flood risk.

Karkheh, the third largest river of Iran, is high importance due to strategic environmental conditions caused by major water and agricultural projects, industrial and urban water supply. Since the probable morphological             #                        #   # =                       # =               #    #   can affect many water utilities such as ponds and irrigation channels, therefore in the present study, in a                                 #  =                  /   V/    # X #  K   +             erosion and sedimentation and some of its features such as changes in geodetic, cross-section shape of river and total sediment load were all examined and simulated using HEC-RAS model. The simulation period of this research was between 2001 to 2013. The results show that near Karkheh Reservoir Dam, which is upstream studying area the erosion condition of the river is higher but in the middle and lower areas of the river, less erosion can be seen. Furthermore, in the simulation of sediment transport functions Ackres-White, Larsen and Engelund-Hansen have offered better results regarding erosion and sedimentation changes of river. Also morphological studies of Karkheh River showed that construction of Reservoir Dam has failed to prevent the displacement of the central axis of Karkheh River. The results of this survey can be a good reference for the condition of Karkheh River and the effects of constructing Reservoir Dam on its condition for various engineering projects, dewatering and water transport.

Global warming caused by emissions of carbon gases into the atmosphere is a serious threat to sustainable development in developing countries Such as Iran. Carbon sequestration in terrestrial ecosystem is a sustainable approach, with no environmental risks. This research was conducted to assess its impacts on relieving climate change effects. Soils have a good capability in storing carbon. Herein this research, carbon sequestration was assessed in Sorkhehhesar Jajrud. Cupresus arizonica, pinus eldarica and rangeland plants were cut dried and sent to laboratory. Meanwhile soil samples were taken and sent to lab too. Based on random systematic statistical method, 6-10 sampling plots of 10 x 10 m. size were allocated for each species at planted and unplanted (control) parts, separately. Soil sampling was made in center of each plot at 0-20cm depth after removing the organic layer of the soil surface to measure carbon sequestration, N, P, K, pH, moisture, bulk density, silt, sand, clay and gravel amount. T-test was used and also Levenn test was used for two independent samples. In order to assess the normality, K-S test was used. it is a best fit test. Also in the end, LSD test was used to assess different parts of plants. It was concluded that pinus eldarica, cupressus arizonica and rangeland plants were significantly traps carbon in the soil. This is normally named as carbon sequestration. pinus eldarica and cupressus arizonica are different significantly in carbon sequestration with outside (no plant)but as for the comparison of them with range land plant there is no significant difference though the rate is much more in the first and second species.

Drought is an atmospheric phenomenon that can effect on various parts of the environment. Groundwater resources is the drought-affected sectors which less are considerate than other sectors. Aspas Plain in Fars province in recent years have a significant reduction in groundwater levels. So, the role of management in this plain is important. In this research, we use a cross-correlation function (CCF) for investigating long-and short-term drought on groundwater resources. For this purpose, the standardized precipitation index (SPI) Monthly (one, three, six, nine, 12, 18, 24 and 48 months) in the period (1985-2010) was calculated, also groundwater resources index (GRI) of the plain during the statistical period (2002-2010) were obtained from 61 wells in the plain. Cross-correlation function showed that short-term drought with delay and long-term drought simultaneously have been effected on ground water resource. Most relationship is between groundwater and SPI 24, which linear regression results showed that almost 80 percent of the average variance water table of Aspas Plain affected by changes in rainfall (SPI 24) and nearly 20 percent of it is influenced by other items.

Geotextiles has been used to conserve eroded hillslopes, decrease soil loss and prepare bed for plant growth over the course of past few decades. In this study we tried to investigate the effectiveness of geotextiles for reducing runoff and sediment yield from an experimental micro-catchment. Two micro-catchment (control & treatment) were selected then the jute geotextile was installed as a buffer along contour line against superficial flow. Then, each micro-catchment was equipped with a flume at its outlet to measure runoff rate during storm events. Other variables (i. e. vegetation cover, soil, surface scree and slope steepness) were monitored during study period. Results showed high runoff and sediment variations during measurement period, so that the maximum and minimum specific sediment yield were equal to 2. 48 and 0. 69 gr. m-2 for events 30-Jan-2015 and 29-March-2015, respectively. Also, compare mean test revealed significant differences in specific sediment yield between two micro-catchments (P<0. 05) but no differences in runoff. High slope steepness along with considerable impervious outcrops are corresponding to high runoff generation even after installation of geotextile. Results from RRE confirmed high performance of jute geotextile in reducing sediment. For storm 29-Mar-2015 the highest RRE was obtained, equal to 50. 49 per cent which indicate tremendous sediment reduction in treated micro-catchment in comparison to control. In this event the geotextile reduced Specific sediment yield by half.

unpredictable, rare and random nature of natural rainfall. The rainfall simulator, as an alternate effective approach, facilitates quick measurements of different hydrologic components. However, calibrated suitable conditions and optimization of governing situation have been rarely taken in to account. Therefore, the Nozzle Type Rainfall Simulator Laboratory was established at Tarbiat Modares University to simulate rainfall similar to storm events happened in Mazandaran Province climate. In the current study, the potency of creating different rainfall intensities by permuting intake discharge, water pressure and nozzle decoration and also their effects on simulated rainfall characteristics were investigated. The results indicated that in different water pressure, the simulated rainfall characteristics were significantly different. The results also showed that drop size distribution and their velocities produced by manufactured nozzle coded as Apd4, in optimum pressure (10 to 50 kpa), were 0. 5 to 4. 7 mm and 4. 8 to 9 m s-1 respectively. Besides, The results also indicated that a rainfall with intensity of 30 to 120 mm h-1 with coefficient of uniformity ranged from 80 to 95% by 27 nozzle spacing 0. 85 m could be properly simulated under intake optimum pressure.

Global warming caused by emissions of carbon gases into the atmosphere is a serious threat to sustainable development in developing countries Such as Iran. Carbon sequestration in terrestrial ecosystem is a sustainable approach, with no environmental risks. This research was conducted to evaluate watershed management mechanical operations including water harvesting, terracing, sediment trapping dams, banquette and furrow in different regions of the country (nine provinces) in atmospheric carbon sequestration and to offer optimal options for these regions. For this purpose, field operations were done for soil, biomass and litter sampling, using systematic randomized method in representative sites and control sites. According to research results, regions in the hillsides of the Zagros mountains including Lorestan, Fars, Kermanshah and Kurdestan showed the maximum carbon sequestration potential in about 54 to 112 ton carbon per hectare. In Hirkani regions in Mazandaran province, water harvesting system operation sequestered about 18 ton carbons per hectare. Watershed management operation in center and west part of country with Iranotorani cover type cannot affect in soil organic carbon stock and rangeland biomass, significantly. In study areas, indigenous terracing and water harvesting systems have higher efficiency in carbon sequestration, respectively and different sediment trapping dams did not show significant effect in this case.

Climate change impacts are very dependent on regional geographic features and local climate variability. Impact assessment studies on climate change should therefore be performed at local or at most at the regional level for the evaluation of possible consequences. However, climate scenarios are produced by Global Circulation Models with spatial resolutions of several hundreds of kilometers. For this reason, downscaling =    #       # #      #                               =              #                      impacts happen. A stochastic weather generator, however, can serve as a computationally inexpensive tool to produce multiple-year climate change scenarios at the daily time scale which incorporate changes in both mean climate and in climate variability. In paper, LARS-WG model were used to downscale GCM outputs and then assessment of the performance were done for generated daily data of precipitation, minimum and maximum temperature and sunshine hours. Study area is Ghare-su basin in Gorgan and the station is      # ‘                     }                      = #        W’¤ VW’’’      # }   =                  #          #         =    # }V          #      ’\ž                 +   #    #                             #          #                    $      =      =                  #          #         =    #      <              =           ? X+ |; <' ¶ ; X' X      result, it is found that performance of model is appropriate for generating daily above listed data in Gharesu basin. So, it is possible to predict the climatic parameters from GCM output using LARS-WG model. Also minimum and maximum temperatures have highest and sunshine hours have lowest correlation.

In recent decades, rapid changes of land use and land cover in the suburbs of major cities in Iran, especially Tehran as the capital, has been growing with important consequences such as the destruction of natural resources, environmental pollution and poor growth of cities. Land use changes and investigation of their causes and factors in a certain time period can be very vital for planners and managers. Purpose of this research is investigation of first grade Markov chain model efficiency for estimating land use changes and land cover for Tehran city and its suburbs during the period of 30 years. In this research multi-temporal LANDSAT satellite images of 1975, 1990 and 2005 were used. Initially, these images were classified in six classes and to the maximum likelihood method. Then, using land cover maps obtained for each period of 15 years, the transformation matrix for land cover classes were calculated between each both time periods. Finally, using the transformation matrix of the first period, the results of land use changes for 2005 was predicted by Markov chain model. Accuracy of the predict with Markov chain model were checked with the help of existing land use maps for 2005. The results showed that the highest percentage of difference is related to arable lands class (0/64622 percent) and the lowest percentage of difference is seen in green space class (0/00551 percent). It is worth noting that in all cases the magnitude of these differences was generally less than 7%, that this number is justified the useful and usable Markov model and its accuracy to predict changes well.

The purpose of this study is, the landslide hazard zonation in Nojian watershed with the models overlay Fuzzy, AHP and GIS the technique. In this study in order to obtain hazard zonation map, were studied 9 factors. This factors in GIS software were prepared to map, and then was classification and weight. These maps were overlapped with the landslides distribution map, until be determined role the classes in landslides distribution. Finally, the 7 factor, lithology, slope, aspect, distance from the fault, land use, precipitation and elevation were identified as factors influencing in landslides the watershed. The maps the landslide hazard zonation was prepared based on these 7 factors and the methods of AHP and Fuzzy Gamma operator 0. 7, 0. 8 and 0. 9 in GIS. The indexe Quality sum (Qs) also were used for evaluate the accuracy of zonation maps. The results the evaluation the maps showed that the amount the indexe Qs for AHP model equal is by 0. 7, and for Fuzzy Gamma operator 0. 7, 0. 8 and 0. 9 is respectively equal is by 0. 75, 0. 71 and 0. 63. Therefore, conclude that the operator the Fuzzy gamma 0. 7 compared to other methods is has better utility in the landslide hazard zonation the Nojian watershed, and is reasonable that, be done take any environmental planning with respect to it.

The field experiments of runoff and erosion process at plot scale using rainfall simulators have been recently more considered, because of both advantages of natural conditions of soil and treatable characteristics of rainfall. A portable rainfall simulator was therefore designed and constructed in Faculty of Natural Resources of Tarbiat Modares University, with a water pomp, three nozzles of BEX: 3/8 S24W and a tripod to get the nozzles to the suitable height of raindrop fall (max 4. 5 m). As the full falling cone, the raindrops ejected from the nozzles at the height of 4. 5 m could cover the whole area of 1×2 m2-plot at ground level uniformly, due to the pressure of the system. The raindrop’ s diameter distribution and velocity were calculated using high speed photography and image processing technique and the uniformity of rainfall on the plot area was then determined using Christiansen coefficient. The results of rainfall characteristics measurements showed that the median diameters of 1. 07, 1. 00 and 0. 98 mm, mean diameters of 1. 14, 1. 05 and 1. 02 mm, mean velocities of 4. 53, 4. 08 and 4. 00 m s-1, kinetic energies of 10. 26, 8. 32 and 8. 00 J m-2 mm-1 and uniformity coefficient of 90, 87 and 91 % were calculated for rainfall intensities of 30, 60 and 90 mm h-1, respectively.

Flood frequency analysis can be considered as one of important methods of flood estimation, forecasting and management in river basins. Structural river engineering and flood control practices are major convenient flood mitigation approaches, whereas, flood frequency analysis is the first steps to achieve this purposes. In this paper maximum and partial duration series as two convenient flood frequency analysis methods were applied in some hydrometric stations in Talar and Babolrud basin in Mazandaran province, regarding to the lack of the recorded flood data series or missing data in hydrometric stations and necessitate of application of more accurate methods. This research has shown that the results of maximum and partial duration series are very sensitive to the length of the data series, which is depends on the existing of the extreme flood values in observation series. It can be concluded that application of partial duration series can have reasonable estimation in the case of not suitable and short period of data series, in comparison with application of maximum series with an enough data series period. This result can show the capability and importance of partial duration series for flood frequency analysis in hydrometric station with short duration data series.