فهرست مطالب mahmood habib nejad

Prioritization of sub-watersheds and different areas has an important effect in watershed management. The purpose of prioritization of sub-watersheds is to provide a pattern for control and decrease flood hazards and evaluating the role of each sub-watershed in peak discharge of outlet flood hydrograph. In this study, Talar watershed was selected as study area, because of several floods was occurred in it and then factors affecting floods like rainfall hyetograph for different return periods, flow length, slope percentage, land use, soil hydrological group, amounts of CN and time of concentration were recognized. By combining ArcGIS software and ModClark hydrological model, the potential of flooding in Talar watershed classified into five classes: Very Low, Low, Medium, High and Very High within three return periods of 25, 50 and 100 years. The results showed that the contribution of sub-watersheds in flooding potential will be not only affected by its area but also the location of each sub-watershed and flood routing in main reach have remarkable effect on flooding regime of the watershed. Runoff production potential maps indicate that runoff production potential from downstream to upstream of the watershed is increasing and Chashm sub-watershed in Southeast of the watershed is considered as the most effective area and unit in flooding of the whole watershed because of heavy rainfall, high slope and large curve number (CN).

One of the most important consequences increased radiative forcing due to anthropogenic activities is global warming, that created varied and challenging changes such as climate change on ecosystems. Predictions show that the increased radiative forcing will continue. Regarding to the existence of several climate models and error correction methods, selection of the right model is one of the key challenges. In this study, the accuracy and efficiency of the fifth report on regional climate models including CanESM2, CSIRO Mk3, EC- EARTH, IPSL, MIROC51, HadGEM2, MPI, NorESM1 and GFDL and statistical downscaling error correction methods including Linear Scaling (LS), Change Factor (CF), Distribution Mapping (DM),  Local Intensity Scaling(LI), Power Transformation (PT) and Variance Scaling (VS) Using T and F tests, the Taylor diagram and 10 statistical indices during two control (1956-2005) and validation (2006-2015) periods were assessed in Birjand station. The results show that; comparing the average of monthly period increases the efficiency of models and methods exaggeratedly. The best model is different based on statistical indicators and time series period. CF downscaling method is not accurate in validation period. LS and VS downscaling methods are appropriate selection for precipitation and temperature parameters respectively. Also, average accuracy of all models for both precipitation and temperature parameters is better than a single model. MPI and Earth climate models have good performance in simulating precipitation and temperature data.

Different models have been designed to simulate incoming floods into urban areas from rural areas, one of the models is the EPASWMM. Mashhad urban watershed with 8 inde-pendent subbasins and area of 2,472 hectares, located in south of Mashhad city . Study area is the residential area of Mashhad Paydari township (Area= 95.6 ha) that located below the M2, M3 and M4 subbasins. Due to high peak flood events in M2, M3 and M4 subbasins, the capacity of urban transmission channels in the Paydari township is’nt suf-ficient and after every rain, a lot of runoff enters the residential areas. The purpose of this research is evaluate the efficiency of EPASWMM model in simulating runoff. The study area was divided into 12 hydrological units (OUT1 to OUT12) and after determine of input parameters of the model, the runoff gathering network in the form of nodes-channels was introduced into the model. Four rainfall events were used to evaluate and calibrate the model with (NS), (RMSE) and (R2) coefficients. In the calibration section of the model, the value of the (NS) coefficient for discharge in the first and third events was 0.94 and 0.92 respectively and for runoff height, 0.9 and 0.86, respectively and indicates simulation accuracy of EPASWMM model in both parameters. The results of the model evaluation section for the second and fourth events shows that the NS and R2 coefficients for three parameters of discharge, height and runoff were from 0.78 to 0.9 and 0.73 to 0.89 and indicates a large correlation between observational and simulated data. Flood reduction scenarios in hydrological units have been investigated according to the simulation results.

This study examines the relations of structures and shapes of streambed evolution after dam break floods. A flume was used to simulate dam-break floods with variations of initial upstream water levels and variance, from uniform to graded, of the bed sediments. Detailed measurements of the evolution and composition were made during these experiments. The data indicate that intense scour occurred immediately downstream of the “dam break” in both uniform and graded sediments. The resulting bed surfaces of graded sediments showed coarse-fine-coarse structures in the areas with the lowest scour and highest deposition and various type of cluster (i.e. line and heap). This pattern was not observed in beds of uniform sediment. The scour hole changes from circular to oval-shaped in both uniform and graded sediments with increasing bed slopes. Keywords: Dam break, Experimental, Bed-surface composition, Graded and uniform sediment, Scour.

Varied flows such as flooding resulting from dam break can happen due to earthquakes, seepage, bombing, overtopping, mistake in design and project performance as well as causing financial damages and human losses. Unsteady flow during flooding events has a high impact on flow field pattern, sediment motion, ecology and also, distribution of contamination in the river. In this study, the impact of various slopes, sediment diameters and unsteady flows with different discharges on sediment transport were carried out at the flume with 12 m length, 0.5 m width and height. In this research, two type of uniform sediment particle with 10 and 15 mm in diameter were spread over the bed of above mentioned flume with slope of 0.01 and 0.02. To build a dam physical model, a mechanical lift-gate was used at 2 m from the upstream inlet of the flume. Potential hydrostatic initial conditions of the fluvial experimental model resulted from dam-break was based on using three water depths of 35, 20 and 12 cm at the gate upstream and one water depth of 3cm at the downstream of the gate. By considering the above mentioned procedures, fluvial flows were produced and have been used with discharge between 0.07 to 0.66 m3/s. The result showed that by increasing the sediment particle size 1.35 times the sediment transport have been reduced by 1/4 for 35 cm upstream water depth and also by increasing the slope by 2 times from 0.01 to 0.023 for sediment with 15 mm and with initial upstream water depth condition was 35, 20 and 12 cm the sediment transport have been increased 3.42, 1.83 and 3.38 times respectively. The above mentioned points show the significance of fluvial flows and their effects on sediment transport and therefore the morphological changes of rivers. Result has been shown that high sediment transport rate and bed evolution was resulting from positive wave head and after that, sediment transport rate have been intensity decreased.

Soil salinization is a world-wide land degradation process in arid and semi-arid regions that leads to sever economic and social consequences.
We analyzed soil salinity by two statistical linear (multiple linear regression) and non-linear (artificial neural network) models using Landsat OLI data in Agh-Ghala plain located in north east of Iran. In situ soil electrical conductivity (EC) of 156 topsoil samples (depth of 0-15cm) was also determined. A Pearson correlation between 26 spectral indices derived from Landsat OLI data and in situ measured ECs was used to apply efficient indices in assessing soil salinity. The best correlated indices such as blue, green and red bands, intensity indices (Int1, Int2), soil salinity indices (Si1, Si2, Si3, Si11, Aster-Si), vegetation Indices (NDVI, DVI, RVI, SAVI), greenness and wetness indices were used to develop two models.
Comparison between two estimation models showed that the performance of ANN model (R2=0.964 and RMSE=2.237) was more reliable than that of MLR model (R2=0.506 and RMSE=9.674) in monitoring and predicting soil salinity. Out of the total area, 66% and 55.8% was identified as non-saline, slightly and very slightly saline for ANN and MLR models, respectively.
This shows that remote sensing data can be effectively used to model and map spatial variations of soil salinity.

Vegetative buffer strips include a special plant being passed by the flow before entering the waterbodies; so, it causes runoff volume reduction, accumulated pesticides and other pollutants of the flow by infiltration, uptake and sediment deposition. The present study has been conducted with aim to evaluate and comparing the impact of vetiver grass, native turf grass of Sari (Mazandaran) and a combination of the two mentioned species on the efficiency of vegetative buffer strips in reducing the surface water pollutants including sediment, nitrate and phosphate. The experiments were carried out using 1×10 m experimental plots and producing artificial runoff with a flowrate by 1.65 l/s during a year. the vegetative buffer strips used in this study reduced the runoff volume by 35-90%, sediment concentration by 42-94%, nitrate concentration by 35-88% and phosphate concentration by 28-95% so that, all maximum efficiencies were related to the treatment of vetiver grass-turf grass. According to the results, the vetiver grass has a high efficiency in reducing and controlling the runoff pollutants; but, due to the probability of the creation of concentrated flow among the bushes of vetiver grass, using a resistant plant adapted to the region climate with a density and uniformity similar to the turf grass is recommended to make the flow uniform and sheet and consequently increasing the efficiency of vegetative buffer strips to reduce runoff volume and pollutants before entering the runoff to the surface waters. Also, periodic mowing of the plants is given as an effective strategy to deal with the role of vegetative buffer strips as the source of nutrients and sediment.

As a cansequence of Marun dam construction on the Jarrahi River, qualitative and quantitative changes of inflow is an ecological threat on wetland ecosystem. In order to prevent the long- term negative impact of the projects on the ecosystem, it is necessary to assess the environmental flow and optimum water allocation for different uses. In this research, environmental flow indices were investigated using hydrological analysis of wetland inflow at Jarrahi River. Environmental flow estimated in Shadegan wetland are 6.83, 1.54 and 3.18 m on Montana method, environmental flow is estimated 1.54 and 3.6 m respectively. The results have shown that environmental flow indices were decreased after dam construction in all hydrometric stations. 3/s based on duration curve, Aqua France law and Smakhtin methods, respectively. Base 3/s in first and second part of year.