مجله مهندسی و مدیریت آبخیز
سال هشتم شماره 2 (تابستان 1395)

Flood is a sudden happening and quick and destructive event that causes death and financial sensible and unsensiable damages in different parts on the world and Iran annually. Control or decreasing these destructive impositions needs precise and accurate studies. So, recognition of the places with runoff generation potential is very important. In current study, two major aims of investigation of the application of distributed ModClark model in flood hydrograph simulation and determination of flood source area in distributed and sub-watershed condition were investigated in the Khanmirza watershed, Chaharmahal-e-Bakhtiari Province. For this reason, at first, inputs of model were extracted by ArcGIS 9.3 and then model was calibrated and validated. In next step, in order to determine flood source area for cell units and sub-watersheds, by applying "Unit Flood Response" method, at first, design rainfall with return periods of 25, 50, and 100 years at the Aloni station were extracted and then influence of each cell and sub-watershed on output hydrograph of the outlet watershed were obtained. The results of model based on comparison between equal-width discharges show that at validation step, the model was simulated the flood hydrograph with high precision with root mean square error, efficiency coefficient, and R2 of 1.53, 0.89, and 0.74, respectively. Also, according to the results of current study, based on the flood volume relative error, peak discharge, base time, and time to peak, ModClark model had lower error in predicting the flood volume and peak discharge. The final results showed that flood source area increases in sub-watersheds from downstream to upstream, while it doesn’t follow any distribution in cell units.

Site selection is the most significant and fundamental process in dam construction. Site selection of dam is one of the most important and effective steps of project implementation. Optimal site selection impacts on reducing the costs of dams establishing. Today, this matter is considered by managers and decision makers. So, different methods apply to site selection. Different parameters are important in text of site selection such as the sub-basins characteristics and hydraulic characteristics. This research determined the optimal location of stone–mortar dams implementation based on nine effective criteria in ten sub-watersheds in Yakhlaqan Makoo region. In this research, criteria weighting was done by AHP method. Then in order to implement stone-mortar dams, Priority of sub-watershed is identified by TOPSIS and VIKOR methods. According to the results, efficient criteria of stone-mortar dams site selection were the catchment area and channel length with 0.191, 0.204 weights. While, the road distance and villages distance were the inefficient criteria with 0.033 weights. The results of both methods identified sub-basins D1, D and H as suitable sub-basins to site selection. The purpose of this research was introduction of the decision support system techniques in identifying and ranking suitable sub-basins in the feild of stone-mortar dam's site selection.

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.

Recently soil erosion and sediment yield has become one of the most important problems of the environment. Soil erosion risk assessment and sediment yield are first steps to confront with this problem. In this regard, various models and methods proposed. What is certain, first of all must be verified the functionality of these models. The present study is carried out to KanSoleghan watershed in order to estimate the soil erosion risk and sediment yield. RUSLE 3D was used in geographical information system platform. Rainfall Erosivity (R), were obtained from monthly and annual data and IDW techniques, Soil Erodibility (K) were obtained from soil data and regin map, Land cover Management (C) using remote sensing techniques (with use of NDVI), LS using digital elevation model, Soil Conservation Practice with using slope percent map. Eventually based on RUSLE 3D model combining these factors together, annual average risk of soil erosion was obtained 22.20 t.ha-1.y to estimate the sediment delivery ratio was used several models, accordingly, the estimated annual sediment yield was overestimated in all models. Sedimentation basin was calculated using statistics gauging stations sooleghan (1.82 tons per hectare per year). Our study indicated that LS factors of the RUSLE 3D model (r2=0.68) were the most effective factors controlling soil erosion in the region. In general, it can be said that the reliability of the used data and used methods is too low and too many uncertainses exist for areliable calculation of soil loss amounts in kan soleghan watershed using the RUSLE 3D Model.

The riverbed and margin vegetation causes to increase in roughness against flow, decrease in average flow velocity, reduce water-energy, and alterations in layer velocity distribution (the flow velocity profile) across the river. In current experimental research, the effect of branching vegetation on the stream flow and bed formation is analyzed. The flow conditions are examined in experimental channel with 7 meter length, 25 cm width and height through different flow rates (3,5,7 lit/s) and slopes under different(0.001, 0.003, 0.005) and densities of vegetation (50, 25 and 12 percent). According to the processed data, it can be implicated that the difference between flow level, substrate, and rate is affected by the types of vegetation density; thereby existence of vegetation causes resistance to flow and depth increment. In all experiments, through the vegetation density increment, the bed erosion increases compared with the primary condition in which the most and least alterations are observed in 50 and 12-percent density, respectively. In the condition of equal flow rate with density increment, the flow depth is increased. The bed particle displacement in the section covered by vegetation is increased through density increment in which flow level in 50 is more than 25 and 12-percent density, as well as, flow substrate erosion and alteration whereas sediment (particles accumulation) is appeared frequently under less density at the end of section covered by vegetation.

Knowledge about optimizing use of rain water under different systems for overcoming water stresses, maximization of crop yield and how their effects is very important. So in this research effect of Rain Water Catchment (RWC) systems under five treatments viz. control (A), eliminated of vegetation and pebble with a gravel filter (B), eliminated of vegetation and pebble without any gravel filter (C), insulated some portion by plastic with gravel filter (D) and insulated some portion by plastic without any gravel filter (E) on activity of photosynthetic parameters have been assessed. The research was conducted in a randomized complete block design with 3 replications for each treatment. RWCs were designed in 8, 5, and 0.5 meters for the length, width and depth respectively, as well as with 9 % downward slope. To facilitate runoff infiltration in root region; a gravel filter was created that was 10 cm diameter and 30 cm depth respectively, in all treatment. Four photosynthetic factor viz. Photosynthetic rate per unit leaf area, stomatal conductance, transpiration rate and substomatal CO2 adsorption were measured after 10 and 23 days after one rainfall event in 2011. Results showed there are significant differences between measured factors except substomatal CO2 adsorption under different treatments. Totally results of this research showed that two Rain Water Catchment systems including insulated some portion by plastic without any gravel filter (E) and eliminated of vegetation and pebble without any gravel filter (C) had maximum positive effect on activity of photosynthetic parameters in Apricot seedlings versus control treatment (A) exhibited minimum activity of photosynthetic parameters in Apricot seedlings. It can say the effect of treatments in runoff delivery to the Apricot seedlings is the cause of obtained aforementioned results.

Aquaculture cylindrical tanks are growing in the world due to the less water consumption and more product efficiency. Study on Hydraulic of this tank is the first step for recognition of sedimentation and solid removal efficiency. This paper is a laboratory study based on flow velocity analysis in different flow depth. The results show that the flow velocity gradient increased in the vector of inlet current toward tank inner bank and due to the incoherence of ISO-velocity layers in different depth, the secondary currents shaped particularly near the tank bank. Also, related to jet current forces, reflected current formed in different parts of the tank pyramid by incidence of jet current to bank of the tank. Local velocity in the middle and beneath depth increased and reflected current depreciate in longer distance on circular current. By increasing the outlet central discharge, the current velocity increased in deeper depth. Due to the local and secondary flows, there is not a match velocity pattern for different discharges in tank. Range of ratio of local velocity to average velocity with depth of 0.2 from tank bottom changes between 0.6 and 1.78 for inlet discharges. Also the results show that the calculated Froude number in each local point related to ratio of local radius to tank radius.

Among the widespread studies have made on drought, rangelands drought has just received little attention. This study investigates the effect of drought on rangelands of Isfahan province. For this, Standardized Precipitation Index (SPI), Rainfall Anomally Index(RAI), Percentage of difference between the measured rainfall and Statistical Index Annual Precipitation(SIAP) were assessed in different time periods and their relation with these type of rangelands production in Isfahan province were studied. In this study, the monthly precipitation data in Esfahan, Meyme and Shahreza stations and forage production data in Charmshahr, Moote, Gardaneshadian rangelands in the period 1998-2007 were used. To investigate the relationship between indices and pastures production, the Pearson correlation was used. The results showed that only in Moote pasture, there were significant relationship and in the other pastures due to the special conditions, there was no correlation between these two variables The results indicate that effect of time periods were more than effect of indexes and spring rains have the greatest effect on the production of rangelands with Artemisia sieberi type in Isfahan province. Finally, the percentage of difference between rainfall in the range 3 month with 0.867 and then RAI 3 with 0.863 and SPI 3 with 0.802 were determined as the most appropriate index of drought.

Identification the source areas of surface runoff and flood prone zones and their impact on residential expansion are important. The aim of the present study is to consider the impact of potential runoff coefficient and flood inundation for different recurrence intervals in analyzing residential expansion for the current land use pattern as well as suitable land use allocation based on the systemic land use planning of Iran in the Ziarat watershed in Golestan Province. The pre-processed Landsat TM image 2010 was used to determine the land use map of the study area and then a suitability analysis is then carried out to establish the potential residential development area in the framework of Iranian systemic land use planning model. The raster layers of slope, soil type, and land use were prepared and the potential runoff coefficient values were determined using the attributes. Floodplain zonation maps were delineated by integrating HEC-RAS and ArcGIS in different return periods. The results indicate that the residential area covers 3.4% of the study area and 9% of the study area was assigned as 1 and 2 suitability classes, according to land use planning model. On the basis of the potential runoff coefficient map, the average runoff coefficient was 0.51%. Based on the combined flood zone maps and runoff coefficient, the flood prone areas will increase for 25, 50, 100, and 200 year floods for both current and determined residential land uses. The areas of flood-secure regions in current residential land use were 318.47, 317.46, 316.44, and 316.44 ha for different design floods respectively. Increasing the return period from 20-50 to 100-200 years lead to an increase of flood zone extent (3.5 ha).

Runoff as one of the water balance components of a basin, is of great importance in watershed and water resources management. Suitable estimation of runoff is requires to determination of runoff coefficient. In this study, runoff coefficient was estimated for return periods of 25 and 50 years using rational, SCS and Cypress-Creek methods for basins up to 50 square kilometers. GIS software was used to overlay layers and basin analysis. Chow, s table was used to correspondence different methods. Due to the lack of compliance with Chow, s table and estimating lower runoff coefficients than reality in most of the study area, Rational Method did not provide suitable results. Cypress-Creek method was also effective in some basins due to it similarity with the SCS method. Average equivalent runoff coefficient of C25=0.37 and C50=0.41 demonstrated high accuracy of SCS method compared with two other methods. According to the soil conservation service method, minimum and maximum runoff coefficients of 25- year return period were related to Chalakrud 1 (0.06) and Safarood 4 (0.61) watersheds, respectively. Also, the minimum and maximum runoff coefficients of 50- year return were 0.1 (for Chalakrud 1) and 0.65 (for Safarood 4), respectively. According to the results of three methods, the lowest runoff coefficients were obtained for watersheds with the highest area and the lowest rainfall intensity.