mohammad fayazmohammadi

In the March and April of 2019, a huge flood covered several provinces in the southwest of Iran and the route of these floods was finally Karun and Arvanroud rivers through Khuzestan province. The purpose of this study is to measure the current speed and direction, temperature, salinity, water level, suspended sediment concentration, sediment transportation, discharge of Karun and Arvanroud rivers in flood conditions. In tidal rivers such as Karun River in Khorramshahr and Arvanroud River at the Iran-Iraq border, the tidal wave causes severe changes in flow pattern, and water level, so that requires continuous measurement over a tidal cycle (about 24 hours) to estimate a net flux of water and suspended sediment. Field measurements were performed on 5th April 2019 in spring tide in two stations in Karun and Arvanroud rivers. Analysis of the data shows that in flood conditions, water level fluctuations reduced drastically, so that the tidal range in Khorramshahr has decreased from about 100 cm to 26 cm. The average of salinity and current speed in Karun and Arvanroud stations were 0.62psu and 2.1psu, and 1.6m/s and 1.9m/s respectively. The direction of the flow, against the usual, was continuously towards the sea. The maximum suspended sediment concentration were 380g/m3 and 67g/m3 at Karun and Arvanroud stations, respectively. According to the above data, the average water discharge in Karun and Arvanroud were 2153m3/s and 7883m3/s, and the average sediment flux were 142 kg/s and 454 kg/s, respectively.

Arvandroud is the most important and only navigable river in Iran. It is where the river flows into the sea and the flow velocity is drastically reduced, causing the deposition of suspended sediments and reducing the depth of the confluence of the river and the sea. This decrease in depth at the entrance of the Arvandroud is such that it has restricted the entry of high-capacity vessels, and its dredging seems necessary to supply water to vessels on this international waterway. In the present study, the effect of dredging the Arvand estuary and also constructing an earthen pier in the Arvandkenar position on the physical parameters of flow velocity and water level fluctuation has been simulated.

For simulation, Mike 21.3's three-dimensional hydrodynamic model was used in two dimensions. This model performs based on the irregular triangular meshing approach and the main computing platform of the model is the HD module, which is based on the numerical solution of 2 and 3-dimensional Navier-Stokes average equations for the non-compressible state, taking into account Bozinsky and hydrostatic pressure. Equations of continuity, momentum, temperature, salinity and density are also considered. In the initial settings, the initial conditions of the model, consisting of temperature and salinity, are uniform for the whole field at 25 °C and 32 psu, respectively. Initially, the water level and flow velocity in the whole basin were considered zero. Due to the small width of the river, the wind effect has been ignored. The model has a sea boundary downstream and a river boundary upstream. Temperature and salinity at the sea border were applied by nesting method from the mother model of the Persian Gulf to the daughter model. The time series of water level fluctuation at the sea border was constructed from the four main components of the tide (M2, S2, O1, K1) related to the SHATT AL ARAB OUTER BAR and applied to the model. At the upper boundary of the river, the temperature and salinity were constant, and 26 ˚C and 2.39 psu were adjusted, respectively. At this limit, the water level fluctuation was adjusted so that the net discharge of the river was 600 m3/s.

In the validation stage, it was found that the result of the root mean square error test for water level fluctuation in Faw was 0.16 m, indicating good accuracy of the model results compared to field measurements. The results showed that if the Arvand mouth is dredged to reach a depth of 8 m and a width of approximately 300 m, the water level after dropping will drop to a maximum of 10 cm near the mouth, and the flow velocity in the dredged area will decrease. In addition, if 33% of the river section in Arvandkenar region is blocked, the difference in water level on both sides of the gorge will be up to 13 cm, and the maximum tidal velocity in the middle of the gorge will reach 0.57 m/s from 0.87 m/s in normal condition.

Dredging of the Arvandroud estuary reduces the flow rate in the dredging canal and this in turn increases sedimentation in the dredging canal. However, reducing the width of the river can compensate for this slowdown and prevent sedimentation. These two methods should be used in combination to reduce the maintenance costs of the channel.

Arvand River is a vast river in the southwest and on the border of Iran and Iraq, which is threatened by a variety of pollutants such as industrial effluents, fertilizers, chemical toxins and municipal wastewater that have adverse effects on the environment and ecosystem. The purpose of this study is spatial analysis of pollution changes in Arvand River using GIS.

In this research, pollution distribution modeling using GIS in Arvandrud river has been used using three-dimensional and hydrodynamic model of Coherence. The continuity equation, Navira-Stokes equations in three dimensions and salinity and temperature transfer equations are solved by separation method. The applied boundary conditions include temperature, salinity and discharge changes for the open river boundary and temperature and salinity changes and the application of tidal components O1, S2, M2 and K1 for the open sea boundary are used in the model.

We call the outputs of the Coherence model, which are in NetCDF format, in the GIS environment, then georeferences the contamination of a specific time (tidal mode), and finally classifies it in the GIS environment.

In this regard, the changes in the pollution of the taxonomic river and the Arvand River are classified on a scale of 1 to 5, with rank 1 indicating the lowest degree of pollution and rank 5 indicating the highest degree of pollution. According to the percentage of area covered by pollution in different stations, it was observed that the highest level of pollution in the first station in the mode of mode and low water with a value of 32.27%, in the second station in the state of low tide with a value of 32.87% And in the third station, it is 28.48% in fashionable and watery mode.

Rivers affected by erosion and sedimentation, which are subject to various changes, including changing the direction of transverse and longitudinal movements, the shortcuts, changing river bed elevation change, change, change size and geometrical properties route pointed. Erosion and sedimentation studies provide the opportunity to identify the behavior of river morphology, the effects of different measures to reorganize its behavioral performance evaluated on quantitative and qualitative data And thereby allows detection of unstable and applying measures to protect and advance engineering measures It was already possible. Arvand River is one of the most important navigable rivers in Iran, and it’s the most traffic place for oil floating which don’t have any system for delivery waste materials and discharging these waste materials in water making oil pollution. Arvand River vast river in southwestern Iran in the Iran-Iraq border and the connections of the dejle, forat and Karun emerged. This study range to which the mouth of the Arvand River in the northern part of the Persian Gulf to the middle of Abadan, about 48 km from the river encompass. In this research for simulating the way of diffusion of oil pollution in Arvand Rood the Arc GIS and surfer software and three dimensional hydrodynamic model (COHERENS) are using, has been employed to solve the equations of continuity and Navier-Stokes in three dimension as well as equations of salinity and temperature. Also for displaying data Ferret software is using. First the model is verfing by using field information and then the result are showing as different senarios for diffusion oil pollution. Including modeling, taking into account different rates for Arvand, spill pollution at different times of the tidal cycle, leaks in different areas and with different loss amounts to is the possible crisis management. In this study, three-dimensional hydrodynamic model of coherence, is used to simulate the flow velocity the Navier-Stokes equations in three dimensions and equations are solved transfer salinity and water temperature separation method. Boundary conditions applied، including changes in temperature، salinity and flow rate، temperature and salinity changes and apply for open border river and tidal components O1, S2, M2 and K1 open sea in the model used for the border. To create files bathymetric mapping of the Armed Forces of hydrographic maps in the scale of 1:25, 000 use software and GIS georeferenced digital interpolation were then. In this study, a computational grid of 80 x 83 meters with an accuracy that range in size 96/52 * 97/48 km covers. One of the most effective tools in the interval erosion and unsustainable use of aerial photographs. The aim of this study was to determine the scope of erosion and sedimentation in Arvand River is using GIS. GIS is a computer-based technology that uses geographic information systems as a framework for managing and combining data, solve problems and understand situations in the past, present and future uses. Software of GIS to identify areas of erosion and sediment has been used in Arvand River And also output the final maps with erosion and sediment pollution is classified. To show the flow rate in different parts of the river, three cross-section upstream, mid-stream and river mouth for the average speed for different times and different places been brought, According to the average upstream speed is observed that the flow rate of water flow rate on the beach on the coast of Iran is Iraq, In the middle sections of the river, the average flow rate on the coast of Iran, Iraq coast, at some point in the middle of the river mouth of the river can be seen that the average speed is lower and on both sides of the river. Because of Arvand River is a tidal river, when the diffusion of oil pollution happen in specified place in high tide, it polluted the outside areas of river, and when it happen in reflow it quickly reached to Persian Golf and controlling it become difficult. The accessible result, represent the effect of tidal on oil pollution diffusion.
Table 1: different parts of the Arvand river coast erosion and sediment
long range (%) long range (km)
62. 57 45. 54 sediment on the beach
26. 75 19. 47 Beach erosion
10. 67 7. 77 Established beach
100 Total Most of the beaches in the study area are related to sediment The length of this range is 62 percent and more of beach fixed and erosion Due to the different horizontal sectioning to speed on the river, and the output flow velocity of the coherence we conclude Where the water flow rate is high, more erosion, and where less water flow speed, sediment more. Where the sediment is covered zone is the highest pollution

Water resources under threat of pollution such as industrial waste, fertilizers, pesticides and urban sewage that negative effects on the environment and ecosystems. Arvand Rood is one of the most important navigable rivers in Iran, and it’s the most traffic place for floating which don’t have any system for delivery waste materials and discharging these waste materials in water making oil pollution. In this research, modeling pollution in the Arvand River using three-dimensional and hydrodynamic model to simulate how the pollution is studied, the Navier-Stokes equations in three dimensions and equations are solved transfer salinity and water temperature separation method. Boundary conditions applied, including changes in temperature, salinity and flow rate, temperature and salinity changes and apply for open border river and tidal components O1¡ S2¡ M2 and K1 open sea in the model used for the border. The results of modeling pollution in Arvand After running the model revealed that the pollution is pollution in the Arvand River according to location and time of release, In other words, in the Arvand River pollution from one point to another and from season to season is different, in fact, pollution is reciprocating mode. Diffusion of oil pollution in Arvand rood is depending to current. And in low tide because of same side of river current with low tide pollution reached to the Persion Gulf with high speed. The results shows, represent the effect of tie on diffusion pollution.