^{1}

^{1}

^{*}

^{2}

In the present study, the Karun River in Khuzestan province in Iran is that is somehow considered the river with the most water in the country was examined. To examine the depth and speed of the flow, which undoubtedly have the greatest impact on the environment and ecosystem of the river, two-dimensional simulation by CCHE2D model was used. In this study, it was observed that, firstly, the changes of depth and velocity along the river have good coordination and the highest changes were observed in the meander and arches. Moreover, due to using two-dimensional model, there is the possibility of examining changes of parameters in the longitudinal and transverse direction that shows the two-dimensional model is an efficient and powerful model in studying river flows.

Karun River is the longest river of Iran with a length of 950 km originating from the Zagros Mountains and after many twists and turns in Khuzestan Plain, it pours into Pars Sea. Karun has been the formation of the earliest human civilizations. Karun has always been of great importance because of its long history in shaping and prosperity of human and indigenous culture of Khuzestan. Today, the water of this old river is used not only to provide drinking water of people of Khuzestan, agriculture needs, and power generation in the upstream, but it has a lot of potential for recreation and tourism. One of the tools to study flow in Karun River Basin is numerical models. For this purpose, one-dimensional and two-dimensional numerical models have been used on a limited basis. Given that the Karun River is among the wide rivers, the use of two-dimensional models and numerical simulations to study compatibility are more compatible with real-world situations. In non-viable models, it is assumed that the flow characteristics change over time. Moreover, in this paper, we assume that roughness distribution is uniform in the entire computational domain. The wind effect is ignored in the calculation. Karun riverbed is generally formed of fine-sand sediments with silt, and in terms of being meander, coastal walls are erosive. In the main part of the Karun River, the soil of the walls is fine-grained texture and prone for agricultural activities. Magrebi (2011), models MIKE21 FM and CCHE2D are compared in simulation the flow pattern in River Bend (Karun). In this study, the pattern of turbulent flow in a range of Karun River has two 180 degree sharp bend in the form of two-dimensional depth-averaged in depth was modeled in unsteady by the mode above. Output Results from the models showed that both models are qualitative models correctly simulating the flow pattern in the study area. Nevertheless, there were differences in the results of the modeling by the above-mentioned software that are due to the quality of solving equations and different abilities of the two [

Karun river basin in terms of hydrology of Iran in general is of the Persian Gulf and Oman Sea basin. Karun is the river with most water in Iran and after Karkheh with 890 km in length is the longest river. Karun River has four main branches called Khersan, AbVanak, AbKiar, and Bazoft. Model of flow simulation module CCHE2D is an average depth two-dimensional developed for Steady and Unsteady flows

Navier-Stokes equation for turbulent average depth two-dimensional flows is as follows:

u and v are the average depth of the components in the x and y of local coordinates;

g: gravitational acceleration;

Z: elevation of the water surface;

h: Local water depth;

_{ }

First, to determine the number of appropriate points of computational grid, flow model was calibrated relative to it and then the calibration of the model for other computational parameters was developed. To calibrate flow models, there are two distinct varieties of parameters available. One is turbulence model that as mentioned earlier in section 3.4 includes: 1) Parabolic models mean depth 2) length complex model of mean depth and 3) two-dimensional k-emodel, and the second substrate roughness using a roughness of the bed defined by n Manning roughness coefficient. Considering that, the aforementioned models aimed at vortices and rotating turbulent flow processes simulating and the flow around hydraulic structures and the impact of such flows on erosion and scour around these structures and since the range intended to do this research has been extensive, during the calibration process, it was observed that by changing turbulence model, there has been no change in the output of models. So, in calibration, the effect of this parameter was ignored due to being intangible. After the calibration of two-dimensional flow model, it is the turn for the final implementation model. At this point, the model was run for a flood for 8 days that occurred in 2015.

By comparing the field view of depth and speed of the flow, it is understood that the magnitude of flow velocity is inversely related to the approximate of depth (

11 points of the path of the intended range shown are selected and for two 96 hours (peak of inflow hydrograph) and 192 hours (end of the hydrograph in eighth day) and the speed parameter against the distance has been plotted. Moreover, in

In all Figures 6-15 that is in all sections and other cross sections in this study,

the left of the diagram corresponds to the left side of cross-section (observer’s seeing angle is along the flow direction). At this point, difference between the level of water in 96 hours (fourth day) in the middle of the inflow hydrograph compared to the level of water in time 192 hours (eighth day) at the end of the hydrograph is nearly 1 meter. In

Hagivar, M.Y., Askar, M.B. and Moalemi, S. (2017) Investigation Flow Depth and Flow Speed Changes in the Karun River. Open Journal of Marine Science, 7, 289-299. https://doi.org/10.4236/ojms.2017.72021