FLOOD ROUTING FOR A SPECIFIC ORIENTATION OF PLANNED DEVELOPMENTS FOR AL-SHAMIYA RIVER IN IRAQ AS CASE STUDY

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1 Journal of Civil Engineering and Technology (JCIET) Volume 4, Issue 2, July-December 2017, pp. 1 12, Article ID: JCIET_04_02_001 Available online at http: // ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed FLOOD ROUTING FOR A SPECIFIC ORIENTATION OF PLANNED DEVELOPMENTS FOR AL-SHAMIYA RIVER IN IRAQ AS CASE STUDY Imad Habeeb Obead Asst. Prof, Civil Engineering Department, College of Engineering-University of Babylon, Hilla-Iraq Aliaa Adnan Khodaier M.Sc. Graduate Student-Civil Engineering Department-College of Engineering-University of Babylon, Hilla-Iraq ABSTRACT Flood routing in branched rivers is an important issue in open channel hydraulic. Consequently, in this work the simulation of flood waves was performed in Al-Shamiya branched River, a fully hydraulic approach was involved by solving the Saint Venant equations using a four-point implicit finite difference scheme as a numerical method. HEC-RAS software was used to conduct the solution of flood routing problem, the hydraulic model of Al-Shamiya river included a main channel with total of 12 cross sections for main channel. The model was calibrated Manning's roughness coefficient adopted herein of (n=0.04) led to the best agreement between the calculated and observed data for the Al-Shamiya river in study area for main reach, also the time weighting factor was (θ=1). The present results indicate that the proposed hydraulic control approach was by deepening the reach by (0.42 m) and modifying the side slopes by (5:1, and 7:1) respectively for control section, or constructing compound section by adding extended berms with filling embankments. Key words: Flood Routing; Saint Venant Equations; Hydraulic Control; Al-Shamiya River. Cite this Article: Imad Habeeb Obead and Aliaa Adnan Khodaier, Flood Routing For A Specific Orientation of Planned Developments For Al-Shamiya River In Iraq As Case Study, Journal of Civil Engineering and Technology, 4(2), 2017, pp // 1 editor@iaeme.com

2 Imad Habeeb Obead and Aliaa Adnan Khodaier 1. HYDRAULIC ROUTING METHODOLOGY Hydraulic flood routing approaches employ conventional Saint Venant equations with both continuity and momentum equations. The continuity equation is [1] : + = ±q (1) and the momentum equation is: +. +g.a +S = 0 (2) in which Q is the flow rate; A is the cross-section area; q is lateral inflow/outflow per unit length; and h is the head of water: h= z+y, where y is the water depth, and z is the elevation of the river bed bottom above an arbitrary datum such as mean sea level. x is the distance along the channel; Sf is the friction slope; and g is the gravitational acceleration; β momentum correction coefficient; and (t) is time. Equations 1 and 2 represent a system of nonlinear hyperbolic partial differential equations, for which analytical solutions can only be obtained under certain linearization assumptions for simple channel geometries and boundary conditions [2]. 2. NUMERICAL SOLUTION METHOD In this research, the weighted four-point implicit finite difference method is selected to solve a Saint Venant equations for its versatility and computing efficiency. The numerical method was performed to the Al-Shamiya branched River at the reach from Shamiya Barrage with reach length of Km. to conduct analysis of the following parameters: maximum flood wave discharge, maximum flood wave elevation, and time of arrival of flood wave to a major section along the river in a case study as shown in figure (1). Figure (1) Schematic diagram of the Al-Shamiya branched river The reach was divided into (55) cross sections, the location of the cross-sections on Shatt- AL-Shamiya and the lengths of sub reaches were illustrated in Table (1) below. 2 editor@iaeme.com

3 Flood Routing For A Specific Orientation of Planned Developments For Al-Shamiya River In Iraq As Case Study Table (1) Location of the cross-sections along AL-Shamiya river [4] Section No. Station Location (km) Sub-reach Length (m) The approximations of the derivatives and constant terms in the four point weighted difference scheme were performed as follows: (1) The space derivative of Saint-Venant equations approximated as: = % / % +(1 ) (3) / % = % +(1 ) % (4) / / ( &. = () *+., -. *+., (() -. ( () *+., -. ( () *+., -. +(1 ) (5) ' / / (2) The time derivatives in Saint-Venant equations (Continuity) were approximated as: ' = ' ' + ' ' (6) / 0 / 0 / = + (7) / 0 / 0 / The friction slope Sf is modeled with Manning s formula: 1 2 = 1 3 = 4 ' 56/7 (8) Where; Sο is the channel bed slope; n is the Manning coefficient, and R is the hydraulic radius(r=a/p), in which P is the wetted perimeter as shown in figure (2). Figure (2) Definition sketch of the wetted perimeter P, wetted area A, and top width T of an open channel cross section 3 editor@iaeme.com

4 Imad Habeeb Obead and Aliaa Adnan Khodaier There are other ways of representing the Saint-Venant equations which were based upon the same hypothesis but expressed in terms of different set of dependent variables. Hence, the water depth (y) in Eq. (2) can be replaced by the water surface elevation (h), The derivative of (h) with respect to the longitudinal axis (x) along the channel yields: % = Since[ 9 = 1 ;]; (9) % = 8 1 ; (10) Therefore; the momentum equation can be now expressed in term of (h) by using Eq. (10) in Eq. (2). Finally, neglecting lateral seepage and lateral overland flow per channel length (q), the constant terms were approximated as: 1 2 ) =>?/0 = ' 5@6/7 (11) B@ = = > 0 C = = ' >' 0 (12) (13) D@ = = ' E@ = ' F@ (14) G@ = = F >F 0 Substituting the necessary terms in the continuity equation yields: (15) ' ' + ' ' 0 / 0 / + / +(1 ) = 0 (16) / Multiplying Eq.(16) by ( xi+1/2) to take the following form: HB I>? I>? I I / =>? B = J++(1 )HB=>? B = J+ KHC I>? 0 / =>? +C I>? I I = C =>? C = JL = 0 (17) Again, substituting the necessary terms in the momentum equation and by multiplying this equation with ( xi+1/2),which yields: / KB I>? 0 / =>? +B I>? I I = B =>? B = L+M(NB 0 C) I>? =>? (NB 0 C) I>? = +PC = I>? (h I>? =>? h I>? = + R =>.1 I>? 2=>?/0 )T+(1 )U(NB 0 I C) =>? (NB 0 C) I = +PC = I I V h =>? +h I = + R => I.1 2=> WX = 0 (18) The terms with subscript (j) in continuity and momentum equations are known either from initial conditions or from the solution of Saint-Venant equations at the previous time step. Since cross sectional area (A) and channel top width (B) are functions of water surface elevation (h), the only unknown terms in these equations are discharge (Q) and water surface elevation (h) at the (j+1) th time step at nodes (i) and (i+1) [figure 3]. Therefore, there are only four unknowns in these equations. All remaining terms are either constants or are functions of these unknowns. As there are N-1 grids in a time line, a total of [2 (N-1)] equations were formed for one time line between the upstream and downstream boundary. There are two unknowns (Q and h) in each of the N nodes giving a total of 2N unknown along each time line. The system of 2(N- 1) equations with 2N unknown require two additional equations to be determinate. These two additional equations are supplied by the upstream and downstream boundary conditions. The 4 editor@iaeme.com

5 Flood Routing For A Specific Orientation of Planned Developments For Al-Shamiya River In Iraq As Case Study resulting system of 2N non-linear equations with 2N unknowns was commonly solved by the Newton-Raphson iterative technique to handle the non-linearity in the equations [3]. Figure (3) Finite difference discretization of (x-t) solution plane representing 1-D flow domain with respect to time 4. CASE STUDY The study area adopted herein is Shatt AL-Shamiya. It was part of Euphrates river in Iraq, the upstream boundary of our study begin from Shamiya Barrage with reach length of Km and an average bed slope range of (7-12cm/km), in which a part of AL-Kifil/AL-Shanafia irrigation project. The designed discharge for the barrage is 1200 m 3 /sec, with upstream level of 23 m.a.s.l., the Barrage consists of radial steel gates, hydroelectric power plant, and navigation lock. The downstream of the study area was bounded by Al Khwarneq barrage which is similar to the Shamiya barrage, but its consist of 5 slots. Table 2 includes all the available hydraulic and spatial information for AL-Shamiya Barrage [4]. Table (2) Hydraulic characteristics for Al-Shamiya barrage Details Value Location Euphrates river/iraq No. and Dimension of slots 6 gates of (6.3 12) m The radius of radial gates 10.5 m Methods of gates operation Manually/Electrically Maximum designed discharge 1200 m 3 /sec Maximum designed level U/S 23.5 m.a.s.l. Normal operation discharge U/S m 3 /s Barrage sill level D/S 16.5 m.a.s.l. Hydroelectric power 6 MW 5. RESULTS AND DISCUSSION In the present work, hydraulic model was developed using HEC-RAS Version 4.1, which performed unsteady flow analysis for networked channels. The observed flow hydrograph accompanying to the steady state flow in control section upstream at the head regulator of Al- Shamiya River was shown in figure (4). The downstream condition used herein considered at the downstream end of the Al-Shamiya river observed stages hydrograph shown in figure (5). 5 editor@iaeme.com

6 Imad Habeeb Obead and Aliaa Adnan Khodaier Figure (4) Inflow hydrograph for upstream boundary (station No. 1) [after (QWRD), 2016] Figure (5) Stage hydrograph in downstream boundary (station No.55) [after (QWRD, 2016] Hydraulic approach involves complex numerical equations with high accuracy however using a lot of data, especially physical data and river specifications. In the study area, the routed flood hydrograph produced by the Saint Venant model with an acceptable accuracy in flood routing required parameters which based on the calibration process performed previously by researchers, such as time step period ( t = 1 day), Manning s coefficient (n =0.04), and finite difference weighing factor(θ=1) Steady State Flow Scenario According to the Directorate of Water Resources in Qadisiyah Governorate/Iraq, the steady discharge was (70 m 3 /sec), the water surface elevation compared to both bank elevations and full bank elevations per each investigated sections along the reach were shown in figure (6) below. Figure (6) Variation of river bank, full bank and water surface elevations for all investigated sections along the study reach for steady flow The bank-full discharge at a river cross section is the flow which just fills the channel to the tops of the banks. Such a discharge therefore marks the condition of incipient flooding [5]. As illustrated from figure (6), almost all sections along reach were sufficient to hold a steady 6 editor@iaeme.com

7 Flood Routing For A Specific Orientation of Planned Developments For Al-Shamiya River In Iraq As Case Study discharge. The last Two section (No.50, and 55) were approaches to critical case with maximum differences in elevations of (0.63m and 0.53 m) respectively. Figures (7, 8, and 9) were demonstrated the differences between full-bank and flow water elevations for upstream, downstream control sections and critical cross-section pointed in station No. (50). Figure (7) Control section (No.1) in Al-Shamiya barrage for steady discharge scenario Figure (8) Section (No.50) along Al-Shamiya reach for steady discharge scenario Figure (9) Control section (No.55) for steady discharge scenario The deficiency in the riverbank's holding capacity corresponding bank-full levels suggested by author, which can be written as: Y Z = [1 \ ]8^ \ ] _ 100% = [1 bcde. \ ] _ 100% (19) Where; ηd is the deficiency of riverbank's holding capacity, YB is the bank-full elevation (m), and yn is the normal depth for a specified discharge in a channel (m).table (3) demonstrated the deficiencies of each section along the reach. Table (3) Deficiency of riverbank's holding capacity for different channel sections Section No. Elev.(m) ηd % editor@iaeme.com

8 Imad Habeeb Obead and Aliaa Adnan Khodaier Section No. Elev.(m) ηd % If the peak discharge exceeds the riverbank s holding capacity, then water would be spread out into the floodplain. Consequently, the more hazard or insufficient section were pointed from section No. (5) to section No. (50) Flood Propagation Scenario The flood wave propagated downstream reach based on existing cross sections was produced, the flood discharge was (200m 3 /sec), the water surface level versus the bank elevations and full bank elevations per each investigated sections along the reach were shown in figure (10). The simulation results illustrated that most of the cross sections were breached except of the control section No. (1), whereas the downstream control section (No.55) has reached a critical state. Figure (10) Variation of river bank, full bank and water surface elevations for all investigated sections along the study reach for flood scenario As shown in figure (10), all sections along reach were breached under the flood discharge of (200 m 3 /sec), except section No. (1), the maximum differences in elevation were occurred for sections No. (1) of (2.71 m and 1.75 m) for both bank-full and normal bank elevations respectively. Figure (11) shows the difference between full-bank and flood water elevations for downstream control sections in station No. (55). Figure (11) Control downstream section (No.55) for flood scenario 8 editor@iaeme.com

9 Flood Routing For A Specific Orientation of Planned Developments For Al-Shamiya River In Iraq As Case Study 5.3. Hydraulic Control along Reach Deepening Critical Sections along the Reach One of the specified development plan of Al-Shamiya reach involves increasing its lower bound normal operation upstream discharge from (20 m 3 /sec) to (75 m 3 /sec). Figure (12) shows the critical section corresponding this state of operation, with the most appropriated trapezoidal section containing the entire existing flow area prior to hydraulic control process. The inclination angle of left side slope of trapezoidal section is (θ1= 83.3 ο ), while the inclination angle of right side slope of trapezoidal section is (θ2=78.7 ο ), the bed width is (B= 51.6 m), and the depth of water about (2 m). Figure (12) Critical section corresponding steady state flow of (75 m 3 /sec) To make control on the reach considered in present work, different values of bed levels for critical cross section No. (50) can be taken and used in the HEC-RAS. Herein, the value was less than the values of the existing bed levels by ( = =0.417m), thus the bed level was( m)and corresponding elevation of flow water was obtained to be (14.41 m).consequently, the riverbank holding capacity improved by decreasing ηd from 95.9% to 94.1% Modifying Channel side slope (H: V) For practical purposes and implementation requirements, a proper side slope was considered to be in convenient with downstream control section No. (55) as a sufficient section for steady flow condition. Figure (13) shows the improved section No. (50) with a combination of increment in flow depth, and side slopes (, where left side slope of (5:1) and right side slope of (7:1) respectively. Figure (13) Improved trapezoidal cross section for steady flow condition The hydraulic and geometric properties of both existing irregular section and most appropriated trapezoidal cross section were given in table (4). 9 editor@iaeme.com

10 Imad Habeeb Obead and Aliaa Adnan Khodaier Table (4) Hydraulic and geometric properties for critical section (No.50) with hydraulic control Section No. 50 Cross section Shape Full-bank depth(m) Water depth(m) Wetted Perimeter P(m) Flow Area A(m 2 ) Hydraulic Radius R(m) 5.4. Hydraulic Geometry Due to Flood Flow By performing HEC-RAS run for flood flow condition for (16 days) and with fixing all the values of the other parameters, it was found that the flood water level would be (22.02 m.a.s.l.) in section No. (50) at the beginning of the twelfth day, as shown in figure (14) below. Remarks Irregular Non-sufficient Trapezoidal (depth increment ) Sufficient, non-applicable Trapezoidal (combination) * Sufficient, and applicable 55 Irregular * with free-board of (0.5m) Sufficient for steady and flood conditions Figure (14) Obtained stage elevation hydrographs (m.a.s.l.) for different time steps ( t) during flood period in critical section No. (50) Thus, the hydraulic control of breached sections along reach (among many possible options) will be based on enlarge the improved trapezoidal section shown in figure (13) above to hold the exceed water quantity produced by flood wave. Otherwise, it would create back water effect that may endanger the surroundings of the reach. The extra flow area was provided to new section by mean of fill embankment along the critical sections (from No.5 to No. 50) to provide berm. The berm was provided in such a way that the bed line and bank line were maintained parallel: G f = g(h 2 h i )g j? (20) In which; Bw is the berm width (m), Zf is the fill side slope, Zc is the cut side slope, and d1 is the full bank depth (m). For channels with silt laden water, the actual capacity of the channel is worked out with 2:1 side slopes in filling, i.e., Zf =2. Let Bw1 is left side berm width: G f? = (2 5) 1.98 = 5.94 q Then, the left side berm width = 6.0 m Let Bw2 is right side berm width: G f0 = (2 7) 1.98 = 9.90 q 10 editor@iaeme.com

11 Flood Routing For A Specific Orientation of Planned Developments For Al-Shamiya River In Iraq As Case Study Then, the right side berm width = 10.0 m. therefore, and to approve the implementation requirements, using the same side berm width of (10.0m). Let the full depth of channel section is (Df), thus: D f = flood water level-channel bed level = = 8.67 m. A schematic compound cross section for modified section No.50 of full bank flow condition was shown in figure (15) below. Some comparative characteristics for sections along studied reach were summarized in table (5) below. Figure (15) A typical schematic of improved cross-section (not to scale) Table 5 Characteristics of breached sections and improved one along studied reach for flood condition Section No. Flow Area (m 2 ) Wetted perimeter P(m) Hydraulic radius R(m) 5-45 * * values are averages for hydraulic parameters. 5.5 Conclusions From the point of view hydraulic, the relevant treatments of study problem, can be summarized: The results obtained herein illustrated that the most applicable hydraulic treatment, would be deepening the reach by about (0.42m) and modifying exist side slopes of critical cross section by (5:1, and 7:1) respectively to be sufficient to steady flow conditions (long return period). Operating the reach such that the (75 m 3 /sec) discharge will produce a water level downstream the AL-Shamiya reach of (14.41 m) at km (29.386). Alternative treatment for flood flow (of short return period) scenario was proposed by presented a compound section adding extended berms and extra flow area to previous cross section by using fill embankments editor@iaeme.com

12 Imad Habeeb Obead and Aliaa Adnan Khodaier REFERENCES [1] Chanson, H., (2004), Environmental Hydraulics of Open Channel Flows, Elsevier Butterworth Heinemann, Linacre House, Jordan Hill, Oxford.UK. [2] Orouji, H., Haddad, O. B., Mehdipour, E. F., and Marino, M. A., (2012), Flood routing in branched river by genetic programming, Water Management, Proceedings of the Institution of Civil Engineers, ICE Publishing, [3] Chow, V. T., Maidment, D. R., and Mays, L. M., (1988), Applied Hydrology, McGraw- Hill, Inc. [4] QWRD (Qadisiya Water Resource Directorate, Ministry of Water Resources, Iraq.), (2016), Report about Shatt Al-Shamyia. [5] Kalpalatha.Ganamala and P. Sundar Kumar, A Case Study on Flood Frequency Analysis, International Journal of Civil Engineering and Technology, 8(4), 2017, pp [6] Rituparna Choudhury, B.M. Patil, Vipin Chandra, Uday B. Patil and T. Nagendra, Assessment of Flood Mitigation Measure For Mithi River A Case Study, International Journal of Civil Engineering and Technology, 7(3), 2016, pp [7] Williams, G. P., (1978), Bank-Full Discharge of Rivers, Water Resources Research, Volume 14 (6). [8] Chow, V. T., (1959), Open-Channel Hydraulics, McGraw-Hill Book Company editor@iaeme.com