1. DAM BREAK ANALYSIS USING
HEC-RAS MODEL

2. PROJECT TEAM
TEAM MEMBERS Hari Prasath. V ( ) Jeya Vignesh. J ( ) Moses Prawin Paul. S ( ) Muthu Kumar. M ( ) TEAM GUIDER Ms. D. Chella Meena., M.E.

3. Need for Analysis:
Dams are built for water supply, hydro-power generation, flood control, etc.,
However, dams may cause catastrophic damage to human life and property if they collapse.
With the help of the dam failure model, the failure modes of the dam can be predicted in advance.

4. Objective: To identify the dam break conditions under various scenario
To identify the flood inundated area in the event of a dam break, using hydrologic software HEC-RAS.
To protect against the loss of life and property damage, flood control measures are suggested

5. INTRODUCTION
Damages to property, human sufferings and loss of life resulting from floods have been increasing annually despite decades of effort and huge expenditure for flood control.
floods alone can cause heavy damages to mankind then the damages due to dam failure will be manifold and catastrophic because of the indiscriminate development of settlement and industries in the flood plain.
There is an old Chinese proverb – “The Great Levee is ruined by ant nest”.
For reduction of flood damages, both structural and non- structural methods are employed

6. STUDY AREA – VAIGAI BASIN
The Dam is located at the latitude 10°03´ N and at the longitude 77°35´ E.
The spillway portion had been constructed with masonry in cement mortar.
The masonry dam is flanked on both the sides by earthen dams.
The Perranai canal prevents seepage and pilferage loss from the River. This canal comes into operation from the year irrigation seasons.

7. EARTHERN DAM
Length of Dam in Left Flank : m
Length of Dam in Right Flank : m
Maximum height of Dam : m
Bottom width of Dam : m
Top width of Dam : m
Top level of Dam : m

8. Vaigai River:
The River Vaigai originates on the Eastern slopes of the Western ghats in Varushanadu Hills in Aundipatty Taluk of Theni District.
The total length of the river is 258kms.
The river flows along FIVE districts
1. Theni
2. Dindigul
3. Madurai
4. Sivagangai and
5. Ramanathapuram

9. Vaigai river basin:

10. Vaigai Dam:
Vaigai Reservoir scheme had been taken up for execution during 2nd Five Year Plan Period and completed in 1958 at a distance 34km upstream of Peranai Regulator.
VAIGAI DAM was constructed to store Periyar water and balancing the flood from Vaigai river during North East Monsoon.
The Storage Capacity of Vaigai reservoir is 6879 Mcft

11. LITREATURE REVIEW
Cameron T. Ackerman et al (2007) have made an attempt in the analysis of dam failure models by providing a scenario generating tool for identifying the resulting hazards. finally discussed the process for gathering and preparing data, creating an unsteady- flow model in HEC-RAS, entry of dam breach parameters, performing a dam failure analysis, and mapping of the flood progression.

12. Ludvig Bjerke et al(2007) simulated results showed a peak discharge of respectively 625 m3/s and 4350 m³/s. The travel time of the flood wave from the Aparan dam to Ashtarak was 1 hour.
Yi (Frank) Xiong(2008) firstly described the dam break in the aspects of theories and models. Break parameters prediction, the understanding of dam break mechanics, peak outflow prediction were shown as the essential for the dam break analysis, and eventually determined the loss of the damages.

13. Sam Crampton(2007) describes that the potential flood risk caused by dam failure is often more severe and can behave very different to that of natural flooding events. His models have enabled flood inundation maps which include peak elevation, flood wave arrival time and flood wave time to the peak for both sunny day and storm in progress failures
Dr. Melvin G. Schaefer(2010) some applications are Downstream Hazard Classification. Inundation mapping for use in developing Emergency Action Plans. Aid in the selection of Design/Performance Levels for Critical Project Elements. Incremental Damage Analysis - an alternative procedure for sizing emergency spillways.

14. Methodology Data Collection
Hydrological Data geometric data, cross section data
Dam Details
HEC-RAS MODELLING
Simulations
Results
Flood Damage Assessment

15. Salient features of Vaigai Dam:
Type : Masonry Cum Earthen Dam
Maximum Height : m (111 ft)
Earthen dam Length : m
Masonry Dam Length : m
Catchment Area : sq.km
Water Spread Area at FRL : Sq.Km
FRL : (MWL (+) ft
Capacity at FRL : Mcum

16. Spill Way
7 Nos of size m x 4.57 m (40’ x 15’)
Type : Lift Gates
Discharging Capacity : Cusecs
River Sluice
7 Nos. of size1.52 m x 2.74 m (5’ x 9’)
Discharging Capacity : Cusecs
Drainage Gallery
1 Number of Size : 1.52 m x 2.29 m (5’ x 7’6”)

17. Dam failure scenarios:
Sliding
Piping
Overtopping
Poor maintenance
Cracking
Internal erosion

18. COLLECTED DATA FROM VAIGAI DAM
1) Dam Details
Type of dam masonry spillway with earth dam flanks either side
Total length of dam ,559 m
Length of masonry spillway m.
Length of earth dam on the right side 2, m.
Length of earth dam on left side m.
Top level of the dam m.

19. 2) Spillway Details
shape of spillway ogee
crest of spillway m.
length of spillway nos. of x m.
3) Breach Information
Maximum water level reached m.
Lowest elevation that bottom
breach reaches m.
Final breach width m. 
Side slope of breach
Time of breach development hr.

20. DERIVATION OF ONE HOUR HYDROGRAPH FROM 13-15 NOV.1992 STORM
rate
time hour
Total run off ordinate in cumec
Base flow ordinate in cumecs
Direct run off ordinate(3-4) cumecs
Unit Hydrograph ordinate 5/net in cumecs
Time from beginning of surface run off hour
11.92
10.00 95
11.00
104 69 35 20 1
12.00
756 73
683
386 2
13.00
1461 76
1385
782 3
14.00
1453 79
1374
776 4
15.00
1313 83
1230
695 5
16.00
1223 86
1137
642 6
17.00
1133 89
1044
590 7
18.00
921 93
828
468 8
19.00
543 96
447
253 9
20.00
402 99
303
171 10
21.00
103
299
169 11
22.00
106
296
167 12
23.00
109
293
166 13
24.00
398
112
286
162 14
1.00
259
115
144 81 15
2.00
250
118
132 74 16

21. 3.00
250
121
129 72 17
4.00
247
124
123 69 18
5.00
127
120 67 19
6.00
131
116 65 20
7.00
134
113 64 21
8.00
137
110 62 22
9.00
141
106 60 23
10.00
144
103 58 24
11.00
147
100 56 25
12.00
151 96 34 26
13.00
214
154 5 27
14.00
166
157 9 3 28
15.00
160 6 29
16.00
163 2 30
17.00 31
EDRO ,110
Pnet = x 1x 60 x 60/ x 106
= M ( or ) 1.77 cm.

22. ANNUAL PEAK INFLOW SERIES OF VAIGAI DAM
Year
Annual peak inflow in 100 cumecs
Order number
7.3.84
18.55 1
14.61 2
13.98 3
9.93 4
7.61 5
7.30 6
7.10 7
8.1.90
4.64 8
4.11 9
3.59 10
3.13 11
2.64 12
2.63 13
2.44 14
2.41 15
2.31 16
2.04 17
1.94 18
1.878 19

23.
1.74 20
1.69 21
1.68 22
1.66 23
1.56 24
1.55 25
1.43 26
1.35 27
1.27 28
1.21 29
1.14 30
1.05 31
1.01 32
0.95 33 34
0.84 35

27. Average Unit Hydrograph

28. The Hydraulic Model (HEC-RAS):
HEC- RAS is a computer program for modeling water flowing through systems of open channels and water surface profiles.
The basic computational procedure of HEC-RAS is based on the solution of the one-dimensional energy equation.
Energy losses are evaluated by friction and contraction/expansion.
The momentum equation may be used in situations where the water surface profile is rapidly varied.

29. HEC-RAS MODELLING Water quality analysis.
Movable boundary sediment transport computations
Unsteady flow simulation
Steady flow water surface profile computations

30. OVER TOPPING
PIPING
HEC-RAS USED TO MODEL

31. CROSS SECTION DETAILS Cross section Elevation 245.9 825 244.925 1720
245.9
825
1720
2320
3000
239.3
4000
238.36
4950
236.36
6000
7000
8050
9000
10000
11200
12400
13900
15260
17000
18500
20000
212.36
21700
23940
203.59
26000
28000
196.8
30150
193.97
32050
192.59
34100
34760
188.96

32. HEC-RAS geometric data

33. HEC-RAS cross section data

34. HEC-RAS cross section graph

35. General profile plot

36. HEC-RAS flow profile data

37. flow hydrograph

38. OUTPUT DATA

39. CONCLUSION
The HEC-RAS results show that the flood can inundate to the range of 1.67 Sq km.
HEC-RAS and DAM BRK results are approximately equal .
If the dam breaks the flood will reach the Madurai within 6 hours
To minimise the damages following remedial measures can be initiated.
Existing important installations may be shifted outside the flood zone in a phased programme
The people living inside the flood zone can be evacuated well in advance to avoid human loss of life.

40. Reference
“GUIDELINES FOR DAM BREACH ANALYSIS” State of Colorado, Department of Natural Resources, Division of Water Resources.
“Dam Break Analysis for Aparan Reservoir, Armenia” Per Ludvig Bjerke.
“Dam failure Analysis using HEC-RAS &HEC-GeoRAS” Cameron T. Ackerman, P.E. & Gary W. Brunner, P.E. Hydraulic Engineering Center, Davis, CA
“A Dam Break Analysis using HEC-RAS”
Yi(frank) Xiong Department of Civil & Environmental
Engineering, Mississippi State University, MS.

41. Thank You !