Development of Flood Routing Model Using Hec-Ras Software for Mutha River in Pune City

International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249-8958, Volume-8 Issue-5, June 2019

S. J. Chate, P. T. Nimbalkar

Abstract: A flood is an overflow of water from the river during was based on statistical correlations between upstream and which water spreads over active and inactive flood plain because downstream gauge stations, measured rainfall in the of natural and artificial reasons of flooding causing damage to catchment area and gauge/discharge data of tributaries etc. property as well as human lives. In Maharashtra, Pune City, faces Flood routing is a mathematical Model for predicting the problems of floods and damages during monsoon. Many bridges changing magnitude, shape and celerity of a flood wave which over Rivers get submerged, resulting failure of communication facility, inundation of the city and surrounding area during this propagates through a river. The main purpose of flood routing period. Maximum flood recorded in Pune city is in the year 2005. studies in most of the engineering works is to calibrate the Unsteady flood model in HEC-RAS was proposed to be set up model for water level and discharge hydrographs for specific using available geometrical and hydraulical data of Mutha River. reach / reaches based on the past data; and to estimate the The Mutha River reach of length 14.905 km is proposed to be changes in the hydrographs under the estimated worst simulated from downstream of Khadakwasla dam to Mula scenarios. –Mutha confluence. The flooding are usually caused by the release of water from the reservoirs located in the Upper reaches of Mula & Mutha Rivers. This paper describes the setting up of II. STUDY AREA hydraulic model In HEC-RAS 5.0 for Mutha River in Study reach. In Maharashtra, every year Pune city faces problems of floods Calibration and validation of hydraulic flood routing model based and damages during monsoon. The problems are generally on the past data of the area under study. By using the developed caused by the release of water from the reservoirs located in model, Estimation of hydrograph for Worst scenarios of 75% and the Upper reaches of Mula & Mutha Rivers. Many bridges 100 % of spillway capacity flood release from Khadakwasla dam. over Rivers get submerged, resulting cut off in Index Terms: Flood routing, Khadawasla dam, Mutha river, Pune, HEC-RAS. communication, inundation of the city and surrounding area during these periods. Up till date Maximum flood recorded in I. INTRODUCTION Pune city is in the year 2005. Floods are the most common and substantial climatic hazard in a tropical country likes India. A flood is an overflow of water. It is natural event that suddenly submerges land especially dry. Flooding is a highly complicated phenomenon of unsteady, non-uniform and gradually varied flow in river channel. Due to flooding the flow variation with respect to time as the wave progressed downstream. It also affects the various channel properties and amount of lateral inflow can also vary. Main problems in India with respect to floods are inundation, drainage blocking due to urbanization and bank erosion. The problems depend on the topography of river and flow phenomenon. Flooding of cities in India is a common and annual event. Proper regulations for maintenance are not followed due to Constructions of several structures in the Fig. (1): Typical Cross section of Mutha River in Pune flood plain areas, therefore artificial flood is created. Thus the city between Z Bridge and Dr. V D Vartak Garden. analytical solution to the problem becomes quite complicated. In most of the states, Flood warning arrangements are It is found that flood problem in Pune city is generally caused provided for issue of for different river reaches. These due to flood water releases from various dams located on warnings would normally include-Existing flood water levels upstream side of Pune city on Mutha River. Typical cross in the reach with reference to the pre-determined danger level section of Mutha River in Pune city with Flood Discharge and Forecast of change in river flood levels (Rise, fall, estimated corresponding flood levels are shown in Fig. (1) period). Before the advent of computers, flood forecasting Khadakwasla reservoir complex consisting of Panshet, Varasgaon, & Temghar dams is located on upstream side of Pune city. Flood releases from Panshet Varasagaon & Revised Manuscript Received on June 28, 2019. Temghar dam are getting collected into Khadakwasla dam on Ms.S.J.Chate, Civil Engineering ,Bharati Vidyapeeth Deenmed Mutha River. Flood in Mutha University College Of Engineering, Pune. Prof.P.T.Nimbalkar, Civil Engineering ,Bharati Vidyapeeth Deenmed River is mainly occurred due University College Of Engineering, Pune. to spillway release from

Published By: Blue Eyes Intelligence Engineering Retrieval Number: E7735068519/19©BEIESP 2302 & Sciences Publication

Development of Flood Routing Model Using Hec-Ras Software for Mutha River in Pune City

Khadakwasla dam. The Mutha River reach in Pune city of possible approaches to the flood routing problems are length of about 15.00 km from Khadakwasla dam to Mula available to engineers, –Mutha confluence is proposed to be simulated for setting up a) Hydrological Routing: of model. Fig. (2) shows the Google map image of study Hydrological routing also known as lumped routing. In this reach. The HEC-RAS is capable of performing routing flow is calculated as a function of time alone. one-dimensional water surface profile calculations for Hydraulic routing methods based on continuity equation and unsteady flow for a full network of channels, a branching flow storage relation. The hydrological routing, directly system or a single river reach. The HEC-RAS has a capacity permits computation of the outflow hydrograph at the to perform steady and unsteady flow water surface profile downstream end of the reach. Hydrologic flood routing calculations, sediment transport/ movable boundary models are conceptual models and it gives approximate computations, water quality analysis and several other hydraulic design computations. Unsteady flood model in results. Hydrological routing are commonly used method in HEC-RAS was proposed to be set up using available current practice due to requires less data and provide quick geometrical and hydraulical data of Mutha River. The Mutha results. Hydrologic routing techniques considered study reach River reach of length 14.905 km from downstream of as a whole. There is still need for two equations to solve for Khadakwasla dam to Mula –Mutha confluence is proposed to the two related variables at the downstream location i.e. water be simulated. surface elevation and discharge. The continuity equation provides one of the equations, but instead of using the momentum equation in the interior of the flow a different empirical relation provides the second equation. Hydrological Routing is applicable for both Reservoir & Channel Routing.

b) Hydraulic Routing: Hydraulic Routing is also called as Distributed Routing. Flow is calculated as a function of space and time throughout the system. Hydraulic methods use motion of unsteady flow equation (St.Venant equations) along with continuity and momentum equation. The main disadvantage of Hydrologic model is that output is limited to discharge of hydrographs at the calibration (stream flow gauging) sites. Hydraulic (distributed) flood routing model, allow the flow rate and water level to be simultaneously derived as functions of space

and time in the channel system. This type of model gives more Fig. (2): Google map Image of study reach of Mutha realistic approximation results of the actual unsteady, non River in Pune city uniform flow propagation in a river and much more information on the flow evolution. The hydraulic flood III. METHODOLOGY AND MODEL SET UP routing are again classified into

A. Methodology 1. Simplified hydraulic model The Saint Venant one dimensional equations describe the 2. Complete hydraulic model unsteady flow characteristics. 1) Simplified hydraulic model The governing equations are: Simplified hydraulic models are based on the conservation A conservation of mass of mass equation and simplified form of conservation of ()Av A momentum equation. +=0...... (1) a) Kinematic Wave Models Kinematic wave model is the simplest distributed model, xt which neglects the pressure and inertial terms, so that the A conservation of momentum equation momentum equation becomes S0 = Sf, assuming the balance v  v  h between the friction and gravity forces. Such a situation may +V + g + Sf = 0.....(2) be accepted if the sufficiently steep slope is present and t  x  x without backwater effects.  b) Diffusion wave model Diffusion wave model - neglects the acceleration terms but Where x is longitudinal axis placed along length of river, t is incorporates the pressure force effect into the momentum the time axis, A is cross sectional area, v is velocity, g is equation. A diffusion model uses the simplified form of acceleration due to gravity, h is the water surface elevation h Sf −=0 above datum and Sf is the friction slope which is calculated by momentum equation as x using empirical equations such as Chezy or Mannings. the inclusion of water surface Due to complexities of the St. Venant equations their solution slope term allows the diffusion was not reliable, and various simplified approximations of models to describe the flood wave propagation continued to be developed. Two

Published By: Blue Eyes Intelligence Engineering Retrieval Number: E7735068519/19©BEIESP 2303 & Sciences Publication

International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249-8958, Volume-8 Issue-5, June 2019 attenuation (Diffusion effect) of the flood wave, and accounts Manning’s roughness coefficient ‘n’ was used as roughness for backwater effects. As this models doesn’t consider Inertial parameter. Separate values of ‘n’ are used for within the banks terms of momentum equation and therefore, is limited to slow & the reaches beyond the banks because of the over-bank to moderately rising flood waves in channels of uniform reaches of river are rougher than the channel, due to trees and geometry. agricultural crops. In case of Mutha model for Pune city for 2) Dynamic wave model calibration Specific event i.e. flood of year 2004 and 2005 A complete St.Venant equation are used, in the dynamic was selected to run in unsteady flow model. The event has full wave model and represents the most complete range of flows from low to high and back to low flow. Then one-dimensional distributed routing model for flow Manning’s ‘n’ values are varied and adjusted to achieve gauge propagation along the channels. discharge curve matching at study locations. Value of ‘n’ used for the over-bank was 0.035 and 0.03 for the main channel. B. Model Setup D. Validation of model The reach of length 14.905 km of Mutha River from Model validation is the process of demonstrating that a given downstream end of Khadakwasla dam to the Mula –Mutha site- specific model is capable of making “sufficiently confluence is proposed to be simulated. accurate “simulations, although “sufficiently accurate “ can There are four main steps are involved in creating a hydraulic vary based on project goals. Considering the data for model model with HEC-RAS: validation year 2006 & 2007 is selected Entering Geometric data For Mutha river only one reach is selected for study purpose. IV. DISCUSSION OF RESULTS Total reach length is about 14.905 Km. Total 13 cross sections have been entered for the entire reach of Mutha River After setting up the model the trial runs are done for the model within Pune city. The Station identifier for start of reach is calibration. The calibration of the model was found as (D/s of Khadakwasla dam) 14.905 and end of reach is 0 satisfactory. Further study runs were made with the calibrated (confluence with Mula river). Station identifier for Dattawadi model. G.D. station is 3.875 and for Main Pune city area is 1.906. A. Findings of analysis and calibration Entering flow data and boundary conditions Inflow hydrograph- Actual Rating curve and Rating curve obtained by Model Flood water Release from Khadakwasla dam is considered as have been plotted and shown in Fig. (3). Actual flood inflow hydrograph into the river. hydrograph and Model flood hydrograph obtained by model Internal Boundary Conditions- at Dattawadi G.D. station is shown in the Fig. (4). The actual Uniform lateral inflow hydrograph is considered as an water level and the level obtained by model are shown in table internal boundary condition. This option permits bringing in a no: I. flow hydrograph and distributing it uniformly along the river reach between two defined cross sections. This condition is used to enter the inflow into the river from free catchments. Downstream Boundary Conditions- Normal depth option can only be used as a downstream boundary condition for an open-ended reach. Manning equation is used to estimate a stage for each computed flood. For this condition it’s needed to enter a friction slope for the reach in the vicinity of the boundary condition. The slope of the water surface is that the sensible estimate of the friction slope. This condition employed as downstream boundary condition at the end of river system station i.e. at 0. The friction slope adopted for model is 0.0001. Initial conditions- Not only boundary conditions, but it is necessary to establish the initial conditions of the system at the beginning of the unsteady flow simulation. Initial conditions consist of flow and stage information at each of the cross sections. Initial Fig. 3 Rating curves for Dattawadi G.D. station. conditions flow values must be consistent with all inflow hydrographs. Performing the hydraulic calculations A computational interval of 1-5 minutes was used for the model runs. Necessary trial runs were made with different time intervals to confirm the accuracy and stability of results. C. Calibration of model Roughness coefficients are one of the most important variables used in calibrating a hydraulic model. By assuming influence of the resistance of hydraulic structures is limited,

Published By: Blue Eyes Intelligence Engineering Retrieval Number: E7735068519/19©BEIESP 2304 & Sciences Publication

Development of Flood Routing Model Using Hec-Ras Software for Mutha River in Pune City

Fig. (4): Comparison of actual and model hydrograph obtained during calibration. Fig. (5): Hydrographs developed for Scenario generations. I. Actual water level and level obtained by Model a) 75% of spillway capacity flood release from Control Flood Flood Levels Khadakwasla Dam. (Scenario – I) level control control obtained discharge Levels from model Table No 2 shows the model output for this scenario. The (cumecs) (m) for Flood 75% flood release from Khadakwasla dam is considered as (m) control inflow hydrograph on upstream side at river station 14.905. discharge. From observing the results it is found that when 75% capacity flood (2081.75 cumecs) is released from Khadakwasla dam, Alert 566.90 544.55 544.59 the maximum flood estimated on downstream side at River Danger 1133.76 545.90 545.89 Station 1.906 (near Late master Karambelakar chowk) is 1435.69 cumecs. This represents that there is flood Disaster 1700.68 547.16 546.99 attenuation is 646 cumecs. It is observed that water level at peak discharge is 546.54 which is 0.64m more than Danger B. Estimation of Flood release hydrograph of Worst level. Fig. 6 shows hydrographs for scenario I. scenarios. In the year 2005 the maximum flood was recorded at Vithalwadi GD station and also for maximum days flood water has been released from Khadakwasla dam during this same year. For estimation of hydrograph of worst scenarios have been derived by numerically extrapolation of actual flood release hydrograph in year 2005 by considering these facts. For estimation of worst scenario hydrograph generations flood releases of 100% and 75% of spillway capacity of Khadakwasla dam are selected. The maximum spillway capacity (100%) of Khadakwasla dam is 2775 cumecs and 75% capacity is 2081.25 cumecs. We have selected time period of 11 days with 12 Hrs intervals for our scenario generations. Extrapolated hydrograph for 75% & 100% of spillway capacity flood release from Khadakwasla dam is shown in Table no 2. This flood hydrograph is entered Fig. (6): Model hydrographs for scenario I. as the Upstream boundary condition and the model is run and for these Worst scenarios flood hydrograph has been b) 100% of spillway capacity flood release from estimated. Fig no 5 shows developed Inflow hydrographs for Khadakwasla Dam. (Scenario – II) scenario generations. Table No 2 shows the model output for this scenario. The 100% (2775 cumecs) flood release from Khadakwasla dam is considered as inflow hydrograph on upstream side at river station 14.905. From observing the results it is found that when 100 % capacity flood is released from Khadakwasla dam, the maximum flood estimated on downstream side

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International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249-8958, Volume-8 Issue-5, June 2019 at River Station 1.906(near Late master Karambelakar 9 Vitthal 550 546.55 547.52 chowk) is 2017.48 cumecs. This shows that there is flood Ramji attenuation is 758 cumecs. It is observed that water level at Shinde peak discharge is 547.48 which is 0.32m more than Disaster bridge level. It is also observed that Peak flood Propagation time is 10 Tilak 545.9 546.4 547.25 30 Hrs. Fig:7 shows hydrographs for scenario II. bridge ( PMC bridge) 11 Shivaji 551 544.9 546.45 bridge 12 Dengale 549 544.97 546.4 bridge 13 Ambedk 548 544.1 545.44 ar road bridge 14 Sangam 548 544 545.3 bridge

V. CONCLUSIONS 1. HEC-RAS software was found to be very useful for the Fig. (7): Model hydrographs for scenario II. study. In the HEC-RAS there is ease of schematization, setting up of model, model operation and calibration and From the model output for both scenarios it is found that two making changes. bridges in Pune city on Mutha River were submerged in the 2. The time required to Propagate Peak flood wave from Khadakwasla dam to River Station 1.906 (Pune city) is 30 worst scenario I. However four bridges in Pune city on Mutha Hrs. River were submerged in the worst scenario II. Table No 6.7 3. In future if 75% spillway capacity flood is released from Khadakwasla dam, then there will be 0.64 m increase in shows details of bridges on Mutha river and water levels water level than Danger level at River Station 1.906 (Pune obtained from model for both scenarios. city). II. Details showing water level of various bridges on 4. In future if 100% spillway capacity flood is released from Mutha River Khadakwasla dam, then there will be 0.32 m increase in water level than Disaster level at River Station 1.906 (Pune SR. Name Bridg Water Water level NO of e Top level for for 100 % city). Bridge level 75% spillway 5. It is found that for Scenario I Flood, two bridges in Pune spillway capacity city namely Bhide Bridge and Tilak Bridge (PMC Bridge) capacity scenario ii will be submerged due to flood. However for Scenario II scenario i Flood, Four bridges namely S. M. Joshi Bridge, Z Bridge, Bhide Bridge and Tilak Bridge (PMC bridge) on Mutha 1 Warje 558 552.19 553 River will get submerged. bridge 2 Rajaram 557 548.69 549.75 REFERENCES bridge 1. Husain, A.(2017).” Flood Modelling by using HEC-RAS”. International 3 Mhatre 554 547.76 548.8 Journal of Engineering Trends and Technology (IJETT) – Vol. 50 2. Doiphode, S., and Oak R. (2012). “Dynamic Flood Routing And bridge Unsteady Flow Modelling : A Case Study Of Upper Krishna River.” International Journal of Advanced Engineering Technology., Vol. 3, 4 S.M. 548 547.53 548.43 55-59. Joshi 3. Adewale., P, Sangodoyin., A, and Adamowski., J. (2010). “Flood Routing bridge In The Ogunpa River In Nigeria Using Hec-Ras.” Journal Of Environmental Hydrology., Vol. 18, 5 Chavan 550 547.3 548.5 4. Sankhua., R, Sathe., B., & Srivastava., A.(2012). “ A Case Study On bridge Dynamic Wave Routing And Unsteady Flood Modelling Of Part Of Krishna Basin With Hec-Ras.” International workshop India Water 6 Lakadi 551 547.2 548.6 Week.(2012) New Delhi. bridge 5. D. N. Moriasi, J. G. Arnold, M. W. Van Liew, R. L. Bingner, R. D. Harmel, T. L. Veith “Model Evaluation Guidelines For Systematic 7 Z 548 547.2 548.23 Quantification Of Accuracy In Watershed Simulations”. bridge 6. Hydrologic Engineering Center, 8 Bhide 544.5 547.1 548.2 River Analysis System User’s Manual and “Hydraulic Reference bridge 5 Manual” Version 4.1 January 2010.

Development of Flood Routing Model Using Hec-Ras Software for Mutha River in Pune City

AUTHORS PROFILE

Ms.S.J.CHATE M.Tech(Hydrualics) Student In Bharati Vidyapeeth Deemed University College Of Engineering Pune. She was obtained his bachelor degree in Civil enggineeing in 2014 from Shivaji University, Kolhapur, Maharashtra.

Prof.P.T.Nimbalkar, M.E (Civil) And Working As Professor In Bharati Vidyapeeth Deemed University College Of Engineering Pune.& Having 30 Years Experience In Teaching And 1 Year In Industry. He Is Pursuing Ph.D From Nit,Surat,Gujrarat & Having Publications Of 8 International & 1 In National Journal.