International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 5, May 2018, pp. 372–380, Article ID: IJCIET_09_05_041 Available online at http://iaeme.com/Home/issue/IJCIET?Volume=9&Issue=5 ISSN Print: 0976-6308 and ISSN Online: 0976-6316

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DAM BREAK ANALYSIS OF USING HEC-RAS

B .Balaji PG Student, Department of Civil Engineering, K.L Deemed to be University, Vaddeswaram, Guntur, , India

Sanjeet Kumar Associate Professor, Department of Civil Engineering K.L Deemed to be University, Vaddeswaram, Guntur, Andhra Pradesh, India

ABSTRACT Dams are constructed across the river to create reservoirs and these reservoirs serve multipurpose objectives of water supply and disaster management. Because of siltation and high flood waves, catastrophic failure of dams may occur. In this study HEC-RAS model is used for dam break analysis of Kalyani dam constructed across River near , Andhra Pradesh. In the present analysis, HEC-RAS was used to simulated unsteady flow in the Kalyani dam and results are mapped, in terms of water level in the river and floodplains. The height shape results as of the barrier breakdown model supply a general dimension of the overflow danger and provides nearby intended for emergency alert was prepared. The procedure intended for congregation along with prepare information, create an unsteady-flow module in HEC-RAS model. The area of water spread, depth of water along with probable maximum flood, travel time and plot to overflow succession was assess in this study. All these information predicted from the HEC-RAS model will helpful in defining the maximum height of flood protection structures in the area to protect it from flooding during high floods. The results of the study will be helpful for evacuation planning, estimation of damages and post flood recovery in the area. Keywords: Disaster, Flood, HEC-RAS, Planning. Cite this Article: B .Balaji and Sanjeet Kumar, Dam Break Analysis of Kalyani Dam Using HEC-RAS, International Journal of Civil Engineering and Technology, 9(5), 2018, pp. 372–380. http://iaeme.com/Home/issue/IJCIET?Volume=9&Issue=5

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1. INTRODUCTION Dam is barrier constructed across a river for impounding of water in the upstream of dam. The dam the dam act as obstruct, straight or slow behind the flood, frequently create a basin, lake and impoundments in the upstream of dam (Sanjeet et al. 2015). The reservoirs of water serve many objectives like irrigation, drought management, flood management etc. Because of siltation, the reservoirs are losing their capacity to store water (sanjeet et al 2015). The large amount of slit deposition in reservoir and flood influence on dam-break wave propagation is of great importance these days (Almeida and Franco 1994). Flood is a major natural disaster that affects the human around the world, causes loss of lives and property (Das et al . The negative effect of natural disaster can be reduce by providing reliable information to the community through flood inundation maps. Besides identifying future flood prone areas, flood inundation maps are also useful in rescue and relief operations related to flooding. Identifying flood prone area and floodplain management hinges on the use of models and their accuracy, as floods can be caused by a vast array of circumstances and are affected by nearly every component of the natural and constructed environment. As is obvious, floods are impossible to predict with complete accuracy. However, a model that accurately describes the characteristics of the landscape, weather and precipitation patterns, hydrologic and hydraulic principles, and current regional and local conditions will significantly increase the odds of successful early prediction. Dams provide various benefit intended to public, however flood resultant as of the breakdown of construct dam contain and created several of the generally distressing disaster of the preceding two centuries. Limitation of barrier crack measures along with the resultant flood are critical to distinguish the same as fine as falling pressure appropriate to probable dams failure. Development of use disaster act strategy require precise forecast of stream level fine the instant of inundation wield appearance at a certain locations. The HEC-RAS model is one of the most popular hydraulic models, recently used in many studies for dam break analysis, preparation flood inundation maps, flood prone area, water surface elevation map (Knebl et al ). The Results of the HEC-RAS will helps to identify the height of flood prevention structures in the flood prone area. The purpose of the study is preparation of flood Inundation map using REC-RAS model and GIS with prediction of water spread, depth of water along with probable maximum flood, travel time and plot to overflow succession for Kalyani dam located on Swarnamukhi River in Andhra Pradesh.

2. MATERIALS AND METHODS

A. Study area The Kalyani Dam is a gravity dam constructed across the Swarnamukhi River at Tirupati city in of Andhra Pradesh, India. The Dam was constructed during the year 1972 to1977 and dam lies under seismic Zone-III. The design flood of dam is 1614 cumec with 25 Mm3 as live storage between hills which are part of Seshachalam Hill ranges. The elevation of the area varies from 50 to 600 m. The catchment area of the dam is 48.56 sq m. The daily summer temperatures range from 36°C to 46 °C. Similarly the winter temperatures of the parts are relatively low ranging around 12 °C to 14 °C with an average annual rainfall of 918.1 mm. The district receives average annual of 438.0 mm of rainfall through the South West Monsoon and 396.0 mm from North East Monsoon. The vegetation of the area comprises dry deciduous mixed forest with patches of moist deciduous forests in the valleys. The study area and Kalyani dam is shown in Figure 1 a and 1 b.

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Figure 1a Kalyani dam front view.

Figure 1b Study area: Swarnamukhi River.

B. Input data for modeling The input data required for this study is catchment area 25 sq.km. , Max Flood intensity is 8472.78 mm/sec, Cross section of Kalyani dam at Tirupati. Contour details of Swarnamukhi River, alignment details of river and dam. The different characteristics of dam and river relative to topography are also collected from dam authority, data include like Full supply level, design flood etc. The data required for dam break analysis using HEC-RAS, is geographic data that provides a physical description of the area and flow data that provides information about the discharge of the river. The cross section of the river in upstream and downstream of the dam, daily discharge, channel geometry and daily rainfall collected from the Kalyani dam authority. The HEC-RAS and map window software was used in this study.

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C. HEC-RAS Model HEC- River Analysis Software (RAS) developed at the Hydrologic Engineering Center (HEC), which is a division of the Institute for Water Resources (IWR), U.S. Army Corps of Engineers. (This hydrodynamic model allows 1D steady and unsteady flow of river hydraulic calculations. It contains four modules, namely steady flow water surface profile computations, One- and Two-Dimensional unsteady flow simulation, sediment transport/movable boundary sediment transport computations, and water quality analysis [4]. In this study, steady flow water surface profile computation module of HEC-RAS is used to simulate daily water stage of the Kalyani dam. The basic computational procedure is based on the solution of one- dimensional energy equation. The further details on the hydraulic nature of water level computation in HEC RAS can be studied using HEC RAS [9] [10].

D. Boundary Conditions (BC) The assumptions concerning BC are well essential used for barrier crack model, since they might in a straight line concern expand of downstream overflow water. Primary flow with stream water depth value, hydrograph, and downstream limit condition, should be specific in the direction of initialized and scuttle the barrier crack mould. These border line conditions should be appropriately and they should be corresponding to the site situation. The inflow hydrograph for the upstream boundary; 4 excessive effort hydrograph of Probable Maximum Flood (PMF), 2/3PMF, 1/3 PMF, and 1:1000 flood were considered for the overflow simulation. The PMF for the learn dams be firm base on the “PMF Estimation of boundary conditions”. The approximate PMF values were comparing using the local equation to substantiate the principles; the reasonable conventional values were adopted. Primary flow and domestic location such as Swarnamukhi River at the start of the simulation. Downstream BC were establish at a huge remains of irrigate absolute to the impoundment irrigate quantity after the of study dam. For occurrence, approximately 2 km down flow of the Kalyani Dam, the irrigate level of 415 m was set for downstream BC.

E. Empirical Equations The empirical equations are utilized to several parameters allied to dam break. These parameters include, time to failure, breach geometry[11]. It also helps to predict peak breach discharge. The experimental approach relief to numerical information to be analyised as of narration of documented failure.

Table 1 Empirical Equation [9] Investigator Equation for predict MacDonald and Langridge- 푡푓 = 1.124 × (푉푒푟 ) 0.364 Monopolis Froehlich (1995) 푡푓 = 0.0784 × 푉푤 × 0.53 × 퐻푏 −0.9

Reclamation 푡푓 = 0.011 × 퐵푎푣푒 VonThun and Gillette (durable 푡푓 = 0.02 × 퐻푤 + 0.25 erosion) VonThun and Gillette (simple 푡푓 = 0.019 × 퐻푤 erosion) Froehlich (2008) 푡 푓 = 55.7 × (푣푤 9.81 × 퐻푏 2 ) 0.5

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F. Flood inundation mapping Dam-breach floods-inundations map indicates area with the intention of may be floods as a consequence of a barrier breakdown. The maps are used by thick scope of end-users for planning and as a reaction instrument to decide the effect of barrier breakdown in downstream areas. In addition, the incremental areas flooded as a consequence of barrier breakdown were considered for a dam classification exercise. For this study, inundation map were generate using HEC-RAS and Arc GIS. Due to the small volume of the kalyani dam reservoir, very small increases in flood levels were observed downstream of the dam. The background flood (no dam failure scenario) was superimposed with barrier breakdown overflow extents in the maps. Due to minor changes between with and without barrier breakdown scenario under flood conditions, it was deemed to produce maximum flood-inundation extent for downstream creek and floodplain areas. The maps were plotted using the worst-case scenario in ordered to show the major areas to can be inundated. Subsequently, incremental consequence analyses were conduct separately using spreadsheets to assess hazards and dam classifications.

G. DBA simulation by using HEC-RAS In this DBA, using miscellaneous flood command imitation, mutually upstream and downstream boundary condition (inflows hydrographs and evaluation curves, correspondingly) and the gateway breach elevation be recognized. Believe the pipe breakdown preliminary WS at the Headwaters summit phase of 847.00 instead of 741.00 in the preceding imitation as the irrigate altitude can‟t arrive at 741.00 exact at the back the barrier base top of agreed flow situation.

Figure 2 Topographic map Swarnamukhi river and locality area In this topographic map has level plan that use line to illustrate ground surface feature, expanse and height can be agreed in ft or meters. You may require near identify a lot as regards to topography (shape are feature) of the areas mountain, plains, plateaus, human made dam, roads and attraction etc.

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Figure 3 Geometric data in plane in HEC-RAS

Figure 4 Geometric data in workflow section in HEC-RAS

H. Dam failures - period of dam at time of failure

Table 1 Period of Time failure Number Total Of years Cause of failure (%) (%) After completion Over Conduit seepage slides topping leakage 0-1 9 23 16 29 19 1-5 17 50 34 24 31 5-10 9 9 13 12 11 10-20 30 9 13 12 16 20-50 32 9 24 23 22 50-100 3 0 0 0 1

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3. RESULTS The graphics include X- Y plots of the river system, schematic cross sections, profiles, rating curves, hydrographs, and many other hydraulic variables. The standard output table consists of river station, total, minimum channel elevation, maximum water surface elevation, critical water surface elevation, energy gradient slope, top width, Froude number and velocity of channel. User can create table with additional variables.

A. Analysis of Kalyani dam Input for Kalyani Dam is Manning‟s „n‟= 0.033, Left of bank = 654m, Right of bank = 655m, Expansion and contraction coefficient = 0.1 and 0.3 respectively and cross section details is given in table 2.

Table 2 river cross section during the flow Reach Station (m) Elevation(m) 0 654 75 640 150 623 225 612 300 606 375 604 Main 455 605 river 525 612 600 629 685 655

Table 3 Maximum water Surface elevation Velocity Minimum Critical Froud River Q value W S Of flow Channel W S no. Station (m3/s) Elevation (m) Channel (m) (m) Channel (m/s) 51000 9906 580 640.34 0 0.52 0.23 50999 9078.24 580 640.34 586.6 0.52 0.23 50987 8027.29 580 638.24 0 9.35 0.05 50800 7406.1 580 638.28 0 9.23 0.02 1130 12256.9 35 54.35 0 1.37 0.05 730 12082.8 35 54.3 0 1.32 0.07 0 12080.5 35 53.21 0 1.27 0.28 Table shows maximum water surface elevation at different locations of downstream of the dam. Column1 shows the sections at which cross section of valley changes abruptly. Column 5 shows the time of arrival of maximum flow in the given sections. Velocity of flow depends on flow area. The maximum flood was found to be 12080.46 cumec which was at end of the valley at table 3.

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4. CONCLUSION Any natural or manmade disaster mapping and risk assessment is important to serve foundation for the damage assessment after the disaster. The risk assessment methodologies will able to save the human life by providing the critical information to the planning members of the community‟s. In this study dam break analysis was performed using HEC-RAS on Kalyani dam. It‟s difficult and wide-ranging progression and the authentic breakdown procedure is not well unstated. Neither present objective base model nor experimental model can completely describe barrier crack mechanism and impact. The barrier crack device in (Hydrologic Engineering Centre RAS) was apply to Kalyani barrier fracture recreation and breakdown based on given geometric facts. The barrier fracture due to pipe elongate the point phase of soaring irrigates plane levels, which increase the size of menace. However, the DBRK doesn‟t amplify the downstream highest irrigate plane altitude radically at preceding intend PMF. Kalyani barrier crack has better contact from down flow location where is faster the dam in conflict with the similarity of the hydrograph at dissimilar location. In treaty by indifference analysis, the changes of barrier fracture parameter had no much control behind flow Maximum water surface elevation, which can cause from initial cause stream shell distance from the ground, edge condition including the in flood hydrographs and gate breach elevation. The study will benefits future flood management in the catchment by providing the flood inundation maps. The study will help to indentify the height of protection work, to identify the area flooded by water during flooding with return period of flood, emerency plan during flood in the area to save human life and property, to assess the damage in the area after flood and define the flood zone in the downstream and upstream.

ACKNOWLEDGEMENT I hereby get chance to give genuine thank to K. Srinivas Rao for their direction and stable support in providing the data for the study. I am thankful for the valuable advice and their well-regarded assist along with sustain which would be remembering lifelong.

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