Floods have direct impacts on the organisms of rivers and indirect impacts on ecosystems of rivers. In this study we perform a water quality model of the zarjoob river by Hydrologic Engineering Center-River Analysis System (HEC-RAS) model, specifically for Carbonaceous Biochemical Oxygen Demand (CBOD) , Dissolved oxygen ( DO ) and nitrite ( No2 ) based on the hydrodynamic simulation for normal and flood condition  to determine the extent of pollution loading in the river. Results showed that trend of dissolved oxygen in flood conditions was reversed compared to dry conditions and showed a slight increase along the river. Downstream of zarjoob river on flood condition, whenever the BOD decreased, DO concentrations increased from 5.5 mg/L to 6.2 mg/L, indicating that water quality was not as sensitive to variations of the BOD as expected. This study showed that rainy events were important environmental factors positively affecting aeration, which raised the dissolved oxygen content of the Zarjoob River except for nitrite. This paper is the first report of the innovative use of HEC-RAS model Without the help of accompanying qualitative analysis models such as Qual2K, WASP … to simulate water quality in an urban river.

Geometric and morphological characteristics of each river are its main characteristics by which the management planning of the basin and the conservation of natural resources around it is done. Estuaries are formed at the mouth of rivers in a border area between sea and land. Deformation of estuaries due to sedimentation and erosion changes the pattern of river flow. In this research, the hydrodynamic model (HD) is used to calculate the flow rates and velocity and the sediment transport model (ST) is used to calculate the suspended load and bed level. The results of the hydrodynamic model showed that the maximum speed at 17 km of Shalmaneh station (beginning of the third interval) is approximately 4.7 m /s. This value decreases to about 1.5 meters per second as we approach the end of the estuary. Due to the importance of the role of floods in bed changes, the model was implemented using the 25-year flood discharge of Shalmanrood River (355 cubic meters per second) for a period of one year. After that, the river route was divided into three parts and the behavior of Shalmanrud river was studied according to the deformation created in the sections of each part. The maximum amount of sediment in the first part is 0.41 m in non-flood condition and 1.1 m in flood condition. In the second part, sedimentation increases and in non-flood state reaches 0.8 meters and in flood state reaches 2 meters. In the third part, the amount of sediment will be more than the first and second parts. The maximum amount of sediment in this part is 0.53 m in non-flood condition and 1.4 m in flood condition.

Growth irregularity and yield reduction in some transplanted rice growing area treated with thiobencarb (TB) has been reported particularly if TB is applied in non-flooded conditions, without any more information. This experiment was carried out in order to study the effect of time of herbicide application and time of flooding on response of rice and weeds to TB doses. The experiment was laid out as a factorial split-plot in a randomized complete block design with 3 replications. Treatments included factorial arrangement of time of TB application (before and after transplanting) and time of flooding (before and after TB application) as main plot and TB doses (0, 1, 1.5, 3, 4.5 and 6 kg.ai.ha-1) as subplot. Results showed that TB efficacy in barnyardgrass and sedges control in 4 week after transplanting was similar and in 6-week after transplanting TB efficacy on barnyardgrass control was better. Irrespective of time of herbicide application, the dosage required for 50 or 90% barnyardgrass and sedges biomass reduction was less in non-flooded condition compared with flooded condition, but herbicide selectivity on rice decreased in non-flooded situation. In waterlogged soil that the experiment was carried out, TB caused mortality of transplanted rice seedlings, the maximum 12% and 4% when TB was applied before and after flooding and also 9% and 5% if TB was applied before and after transplanting respectively, which occurred in maximum investigated dose. By increasing TB dose 50% more than recommended dose (3 kg.ai.ha-1), and better control of weeds rice leaf area increased and if TB dose was increased more, despite better weed control, rice leaf area decreased indicating phytotoxicity of TB. Overall rice produced 25 and 15 % more LAI and tiller respectively, by applying TB at flooded plots compared with non-flooded plots. Rice height response to TB dose and time of application was similar to leaf area and decreased more if herbicide was applied before flooding. Also productive (panicle-bearing) and unproductive (nonpanicle-bearing) tillers were affected by time of flooding and TB dose, if applied after and before flooding the most productive and unproductive panicles were produced respectively. Grain yield, biological yield and harvest index trends were presented by three parameters Gaussian model (R2≥84%). Based on these models, by increasing the TB rate these traits increased and then decreased, but reduction in lower doses of TB occurred if TB was applied before flooding. Overall, based on the results of this research, TB cannot be recommended in paddy waterlogging soils if they are facing flooding limitation in early season when TB is applied. Albeit better weed control in non-flooded treatments TB causes delayed growth irregularity and yield reduction when fields are treated in non-flooded condition. Continuous application of TB in successive years exacerbated TB phytotoxicity.

To study the morphological and agronomical traits and determine heterotic patterns at the reproductive stage of 96 mutant rice genotypes (M2), two separate experiments were carried out under drought stress and flooding conditions at Gonbad Kavous University, Iran, in 2016 using a randomized complete block design with three replications. A factor analysis was conducted to reduce the number of variables to fewer independent factors, and three and four factors were identified under the flooding and drought conditions, explaining 68.3% and 76.05% of the total variance, respectively. Cluster analysis using the selected factors by the Ward’s minimum variance method and Euclidean distance led to grouping of the mutant rice genotypes. The best cutting points of the dendrograms were determined by the discriminant function analysis and four clusters were identified at both irrigation conditions, which were also significantly different. Genotypes of the first and second clusters had the highest yield and its components under the flooding condition. In contrast, under the drought condition, genotypes of the third and fourth clusters were higher yielding and more tolerant to the drought stress. Mutants No. 4, 18, 25, 28, 29, 43, 44, 48, 53, 72, 79, 88, 90, 91, 94 and 95 were present in the first and second clusters of the flooding condition, and in the third and fourth clusters of the drought-stress condition, indicating their superiority over other mutants in terms of grain yield and drought tolerance. The results obtained from this study can be used for selecting suitable parents for hybridization from different clusters to produce new rice cultivars.

The aim of this study was to investigate the variation in concentration of macro- and micro- nutrients in soil and shoots of Quercus castaneifolia seedlings growing in flooded and non-flooded conditions. For this purpose، one-year old seedlings of this species were subjected for 120 days to three different conditions: (i) well-drained control (ii) permanent flooding and (iii) periodic flooding in an experiment as a completely randomized design. The results showed that flooding reduced the ratio of Organic carbon، Total Nitrogen and available Potassium in the soil. Potassium concentration in permanent flooding was reduced to 49% in comparison to control treatment. Also، in the permanent flooding، availability of Fe and Mn increased to 42% and 51% with respect to controls، respectively. Under flooding conditions، nutrient accumulation decreased in leaves of stressed seedlings. In addition، the reduction in N، Ca and Mg in permanently flooded seedlings was greater than those in seedlings growing under periodic flooding. The Zn concentration in leaves diminished as a result of the permanent flooding. In both flooding regimes، Mn concentration in leaves with respect to controls increased 2. 5 times، whereas Fe concentration increased 2. 5 and 3. 5 times، respectively. There was found a positive significant correlation between most of nutrient concentrations of soil and leaf. In conclusion، macro-nutrients in soil and shoot of seedlings under flooding stress were reduced whereas micro-nutrients increased. Taking into account that some macro-nutrient concentrations in soil and leaf of seedlings grown in periodic flooding were greater than those in permanent flooding، it is concluded that for growth of Q. castaneifolia seedlings، periodic flooding is more favorable environment than permanent flooding.

This present study was conducted to determine particle size characteristics of suspended sediments transported by base and flood-flows in the Kojur River in Kojur forest watershed with an area of 50000 ha. Sediment samples were analyzed based on Stokes’ law using a modified pipette and applying the GRADISTAT software. Results showed 81.1, 3.4 and 15.3% for sand, silt, and clay, respectively, in base flow conditions while under flood conditions, the same values were 56.5, 17.0 and 26.5%.

Today, the management of flooding and surface runoff in urban areas is very important. In this study, adequacy of surface water collecting network in Masal city for passing the design flood is considered. The basic information about the climate, topography and land use provide for simulation of surface water collecting network using MIKE SWMM computer model. Hydrologic simulation in RUNOFF block was performed by entering the physiographic characteristics, pattern and the time distribution of precipitation for 10 return periods. For hydraulic simulation, the inputs from junctions and conduits characteristics were entered to EXTRAN block, and also the geometrical properties of the channel, grids, boundary conditions and outlets were fed to the model for simulations. The results showed that existing condition has not been able to pass design flood and this matter causes surcharge and flooding conditions in location of junctions more than 360 minutes. Therefore with technical and application considerations and with a trial and error procedure, adequate sizes of channels for passing design flood was determined so that in occurring of design flood, surcharge and flooding conditions have been omitted completely or become minimum (less than 15 minute) and according to that, the typical sizes of channels for passing design flood were proposed. Also in this, the sensitivity analysis of model was examined in RUNOFF block. Area and the percent of imperviousness with sensitivity index equal 2

Flood can be having devastating effects on watersheds and human life, so, recognize of flood prone areas have a high influences on flood management. The aim of this study is to assessment of flood susceptibility at Talar watershed with an area of 2067 square kilometers. For this purpose some flood conditioning factor such as elevation, land slope, curvature, topographic wetness index, stream power index, average rainfall, distance to the river, hydrologic group of soil, maximum depth of soil, and land-use have been used. Flood conditioning factor have been prepared using related software and then converted to raster format. In the next step the 135 flood location in the study area were determined. These flood location were divided into two groups consisting of 93 locations for calibration and 42 locations, for validation. Then with comparatively analysis between previous floods coordinates and impressive environmental parameters on flood occurrence the probability of flooding for each class of each parameter was calculated. Faunally was obtained the flood risk map of the study area. Based on the flood risk map, the territory was divided to 5 class sensitivity, very high, high, medium, low and very little. The results have been showed that the frequency ratio method with 80% accuracy have high performance in determination of flood prone areas in Talar watershed.

Hypoxia is a potential threat to various horticultural cropsin lands prone to flooding. Citrus is mostly known as a sub-tropical crop that is often exposed to environmental stresses. In order to evaluate response of six different citrus genotypes, including sour orange, rough lemon, Trifoliate orange, Troyer citrange and two local genotypes labeled; CRC1 and CRC2 to flooding conditions, an experiment was carried out in factorial experiment based on a completely randomized design with two treatments including flooded and control plants and three replications. Flooding stress significantly decreased leaf chlorophyll content, and plant total fresh and dry weights (P≤ 0.05). Flooding caused a significant increase in foliar concentration of proline in CRC1 and CRC2 (P≤ 0.05). Guaiacol peroxidase activity was significantly increased in Trifoliate orange. CRC2 and sour orange showed a significant increase in superoxide dismutase activity (P≤ 0.05). The longest survival period in continuous flooding condition was observed in Troyer citrange and Trifoliate orange (more than 60 days); while sour orange was the most sensitive genotype (less than 30 days). The best thriving genotype at the end of recovery period was Troyer citrange, while sour orange showed the least ability to re-establish. The results suggest that among the studied genotypes, Troyer citrange and Trifoliate orange are able to resist for longer periods of flooding exposure. Troyer citrange had the highest capacity to re-establish after being flooded to their critical surviving point. Furthermore, CRC2 tolerated anoxic condition and recovered more successfully than the other sensitive genotypes.

Because of data lacking in the most of watersheds, many researchers applied spatial analysis in GIS environment to study the hydrological and flooding condition. This study aims to map flood susceptibility through frequency ratio technique using some parameters such as digital elevation technique, slope, curvature, topographic wetness index, stream power index, average rainfall, distance from river, geology, soil type and land use in Pole-Doab, Shazand Watereshed, Makazi Province, Iran. First, digital map of all of the parameters were prepared based on raster format using Arc GIS 10.1 and SAGA GIS2 softwares. To prepare land-use map IRS-1C satellite image, ENVI 4.8 software and maximum likelihood algorithm were applied. Then flood inventory map was produced by mapping 95 flood prone locations in the study area using documented information on the May-2003, May-2004 and March-2004 floods. These 95 locations divided into two groups including 67 points (70%) and 28 points (30%) for calibration and validation, respectively. For calibration, flood prone locations defined as dependent variable and ten parameters that are affecting flooding condition were introduced to frequency ratio as independent variables. Then flood probability was determined for each class of each parameter. Finally, obtained weights for each class in GIS were implemented in corresponding layers and using the overlay algorithm, susceptibility and probability maps were prepared. Based on the susceptibility map, study area was divided into 5 classes as very high, high, medium, low and very low sensitivity. The findings of the assessment of frequency ratio histogram indicated that the likelihood of very high and very low flooding classes are equal to 67.86 and zero percent, respectively. Therefore, the obtained frequency ratio histogram confirms the adequacy of the implemented method in flood susceptibility and probability mapping for the case study.