Water Flow Simulation of Tigris River Between Samara and Baghdad Based on HEC-RAS Model

Abstract

This work aims to use the digital elevation model (DEM) or 3-Dimensional surface to model and analyze the water flow in the Tigris River. The first stage of this study is based on filed data acquisition survey at 38 stations. These stations were adopted to implement the one-dimensional steady and unsteady numerical flow models. The HEC-RAS software was used to implement these models. The most important results of the steady-state model were that the maximum discharge and velocity and minimum flow area were 638.17 m 3 /sec, 2.12 m/sec and 301.42 m 2 respectively. These values occurred at station 66+700. While, the minimum discharge and velocity and maximum flow area were 504.5 m 3 /sec, 0.13m/sec and 4758.13 m 2 respectively. The results of unsteady state were analyzed based on the recorded discharge in the year 2018. The maximum and minimum discharge (flow velocity) were 638.12 m 3 /sec (2.42 m/sec) at the stations 94+666+7 and 635.57 m 3 /sec(0.14 m/sec) at station 00+00, respectively. The maximum and minimum Froude number were 0.52 and 0.02 at stations 94+666+7 and 04+800, respectively. These results help to identify the flow choking areas that cause defects. In addition, it can be the base for determining the critical sedimentation stations in which the bed level rises and aggravate the flow choking problem within the considered reach of the Tigris River.

Impact of Dam Materials and Hydraulic Properties on Developing the Breaching Dimensions

“…The average difference between the maximum and minimum values of both cases in the erodibility rate is approximately 0.8. A sensitivity analysis is applied with two scenarios depending on mathematical approaches modified by Froehlich [17] to examine the influence of more sensitive hydraulic factors (represented by the reduction of reservoir capacity) on breach width and time of completing breach as shown in Figures 9 and 10, respectively.…”

“…Two models are needed: the first is a hydrologic model and the second is a hydrodynamic model. The hydrologic model is used to determine the outflow hydrograph which is considered an initial boundary condition to a hydrodynamic model [17]. Many empirical equations are taken into account in 2D HEC-RAS software to calculate the breach parameters and formation time, such as Froehlich's (2008) approach as illustrated in Equations ( 1) and (2) [18].…”

“…Figure8: Variation of breach slope with embankment core in high and medium erodibility rates Also, Figure8shows that the lowest values of side slope and time of the breach and high values of width occur in the case of concrete face dams with high and medium erodibility rates. In contrast, high values of side slope and time of the breach and lowest values of width in the case of homogeneous zoned fill dam with high and medium erodibility rate is considered the worst case because of reduction in the relative compaction.A sensitivity analysis is applied with two scenarios depending on mathematical approaches modified by Froehlich[17] to examine the influence of more sensitive hydraulic factors (represented by the reduction of reservoir capacity) on breach width and time of completing breach as shown in Figures9 and 10, respectively.Figure9displays the relationship between the width reduction ratio and reduced water capacity ratios. It is noted that the maximum reduction in width ratio is 21% at 0.5 reduction capacity.…”

Investigating the Hydraulic Behaviours of an Alluvial Meandering River Reach Between Two Barrages

“…Kayyun & Dagher (2018) [12] presented a study for a reach with a length of 19.5 km lying in the northern part of the Tigris River between Al-Muthanna Bridge and Sarai gauging station at Baghdad city in Iraq and used a model for 2D unsteady flow for calculating the velocity and water surface elevation for the flooding scenarios of flow rate. [13] conducted a field data acquisition survey at 38 locations to examine the water flow in the Tigris River. These stations were selected to develop one-dimensional unsteady numerical flow models using HEC-RAS software.…”

Watershed Delineation from DEM by Model Builder in ArcGIS

“…In the present study, a two-dimensional HEC-RAS model was used to simulate the flood wave resulting from the hypothetical failure of the Al-Udhaim Dam on the Al-Udhaim River, Iraq, including the propagation of the resulting dam-break wave along 100 km downstream of the dam site for the overtopping scenario. Alwan et al [7] used the digital elevation model (DEM) or three-dimensional surface to model and analyze the water flow in the Tigris River. Then, Khayyun et al [8] simulated the catchment area's runoff of Hemren dam reservoir within the middle River Diyala reach beyond Derbendi Khan dam in the northeast of Iraq using the Soil Water Assessment Tool (ArcSWAT2012) model integrated with RS and GIS.…”