mm MCft

1 2 3

y = 0.2292x -

31.047 from

Table 7.1 of

earlier study

5

y = 0.4571x -

67.008 from

Table 7.2 of

earlier study

7

y = 0.939x -

163.65 from

Table 7.3 of

earlier study

9

y = 0.755x -

43.547 from

Table 7.4 of

earlier study

11

y =.0733x1+ 0.4242x2 -

12.2289 from Table 7.5

of earlier study 13 14

1 1941 179.13 10.01 165.22 8.51 270.61 90.45 189.42 99.47 61.67 27.82 236.26 1617.78

2 1942 217.41 18.78 632.29 222.01 584.08 384.80 193.04 102.20 47.65 22.14 749.94 5135.25

3 1943 343.17 47.61 444.92 136.36 247.56 68.81 324.95 201.79 76.70 44.12 498.70 3414.88

4 1944 158.17 5.21 635.89 223.66 331.77 147.88 262.34 154.52 58.28 31.72 562.99 3855.12

5 1945 155.16 4.52 602.54 208.41 383.19 196.17 288.43 174.22 88.76 46.56 629.88 4313.13

6 1946 322.86 42.95 672.82 240.54 504.09 309.69 165.47 81.38 57.47 24.28 698.84 4785.38

7 1947 59.95 0.00 605.58 209.80 374.15 187.68 249.15 144.56 77.04 38.71 580.75 3976.76

8 1948 104.10 0.00 543.06 181.23 279.60 98.90 264.90 156.45 26.52 18.44 455.01 3115.74

9 1949 106.08 0.00 614.10 213.70 295.59 113.90 363.96 231.24 159.01 81.90 640.74 4387.55

10 1950 82.60 0.00 578.91 197.61 141.88 0.00 235.51 134.27 6.01 7.58 339.46 2324.47

11 1951 193.61 13.33 413.78 122.13 385.17 198.03 173.64 87.55 58.99 25.52 446.56 3057.86

12 1952 79.22 0.00 488.02 156.07 303.38 121.23 170.92 85.49 66.89 28.67 391.46 2680.55

13 1953 288.08 34.98 362.96 98.90 824.91 610.94 167.01 82.55 114.31 48.50 875.87 5997.60

14 1954 82.58 0.00 576.06 196.31 514.85 319.79 465.24 307.71 47.63 42.08 865.89 5929.22

15 1955 316.08 41.40 257.55 50.72 444.34 253.59 318.92 197.23 202.43 97.02 639.96 4382.17

16 1956 259.07 28.33 634.47 223.01 300.35 118.38 226.77 127.66 85.26 40.56 537.94 3683.59

17 1957 133.27 0.00 435.70 132.15 776.68 565.65 112.44 41.34 57.91 20.58 759.72 5202.26

18 1958 81.15 0.00 598.92 206.76 477.19 284.43 260.36 153.03 133.00 63.27 707.49 4844.60

19 1959 247.21 25.61 759.34 280.09 749.52 540.15 509.33 341.00 99.14 67.16 1254.00 8586.88

20 1960 216.57 18.59 584.99 200.39 447.37 256.43 291.14 176.26 240.67 111.20 762.88 5223.86

21 1961 228.70 21.37 624.42 218.41 403.43 215.17 339.19 212.54 39.43 29.36 696.85 4771.76

22 1962 197.86 14.30 620.17 216.47 387.62 200.33 364.74 231.83 39.33 31.19 694.12 4753.06

23 1963 163.59 6.45 382.13 107.66 675.05 470.22 172.33 86.56 187.64 80.00 750.90 5141.82

24 1964 263.64 29.38 270.80 56.77 535.43 339.12 409.68 265.76 126.00 71.25 762.28 5219.79

25 1965 190.44 12.60 513.59 167.75 212.11 35.52 188.52 98.78 1.24 2.12 316.77 2169.12

26 1966 167.36 7.31 637.94 224.59 348.71 163.79 381.08 244.17 63.14 42.49 682.35 4672.43

27 1967 280.51 33.25 516.52 169.09 389.25 201.85 100.47 32.31 27.35 6.74 443.24 3035.12

28 1968 82.89 0.00 336.92 87.00 148.19 0.00 258.50 151.62 202.85 92.77 331.38 2269.18

29 1969 134.94 0.00 557.51 187.83 308.99 126.50 335.00 209.38 83.72 47.84 571.54 3913.69

30 1970 141.34 1.35 232.99 39.49 335.00 150.91 120.93 47.75 79.43 30.33 269.84 1847.72

31 1971 257.65 28.01 385.10 109.02 265.77 85.91 114.12 42.61 157.73 63.05 328.59 2250.06

32 1972 181.23 10.49 477.46 151.24 256.55 77.25 184.85 96.01 96.77 42.37 377.36 2584.02

33 1973 115.00 0.00 433.52 131.15 389.78 202.36 69.50 8.93 283.96 113.32 455.76 3120.85

34 1974 226.61 20.89 166.37 9.04 368.37 182.25 194.53 103.32 195.37 84.91 400.41 2741.81

35 1975 284.26 34.10 220.67 33.86 340.86 156.42 376.79 240.93 164.66 85.24 550.55 3769.95

36 1976 96.45 0.00 752.33 276.88 361.00 175.33 209.77 114.83 0.78 3.48 570.52 3906.67

37 1977 188.23 12.10 482.72 153.64 325.63 142.12 124.49 50.45 26.16 7.99 366.30 2508.25

38 1978 338.56 46.55 568.81 192.99 654.01 450.46 89.07 23.70 17.42 1.69 715.40 4898.74

39 1979 231.92 22.11 124.78 0.00 222.26 45.05 219.16 121.92 48.05 24.22 213.30 1460.56

40 1980 279.33 32.97 434.15 131.44 390.25 202.80 174.62 88.29 10.73 5.12 460.63 3154.19

41 1981 187.48 11.92 448.83 138.15 478.47 285.63 285.05 171.67 33.82 23.01 630.39 4316.63

42 1982 192.72 13.12 299.50 69.89 601.30 400.97 139.05 61.43 109.68 44.49 589.91 4039.46

43 1983 250.09 26.27 445.43 136.60 553.29 355.88 430.81 281.71 166.17 89.84 890.31 6096.44

44 1984 181.90 10.64 372.83 103.41 241.30 62.93 182.06 93.91 35.69 16.26 287.16 1966.32

45 1985 135.98 0.12 273.10 57.83 517.28 322.08 112.28 41.22 174.85 70.17 491.42 3365.04

46 1986 134.63 0.00 346.23 91.25 456.33 264.84 118.50 45.92 39.65 13.28 415.29 2843.76

47 1987 217.68 18.85 401.06 116.32 308.90 126.41 156.25 74.42 77.77 32.21 368.21 2521.32

48 1988 174.58 8.97 1265.69 511.54 149.19 0.00 274.78 163.91 83.98 43.54 727.95 4984.70

49 1989 287.55 34.86 528.18 174.42 397.76 209.85 217.13 120.38 2.28 4.66 544.17 3726.26

50 1990 184.08 11.14 369.12 101.72 826.87 612.78 196.52 104.83 165.77 72.49 902.97 6183.12

51 1991 213.38 17.86 549.05 183.96 317.48 134.46 184.11 95.46 69.72 30.84 462.58 3167.58

52 1992 276.85 32.41 457.40 142.07 541.05 344.40 225.74 126.89 18.47 12.15 657.92 4505.15

53 1993 108.50 0.00 474.16 149.73 268.51 88.48 434.37 284.41 137.00 77.73 600.34 4110.90

54 1994 176.36 9.37 571.84 194.38 470.09 277.76 158.62 76.21 81.95 34.16 591.89 4053.00

55 1995 179.60 10.12 501.94 162.43 410.24 221.57 151.27 70.67 272.85 114.60 579.38 3967.34

56 1996 327.95 44.12 390.97 111.70 465.55 273.50 169.79 84.64 39.62 17.02 530.99 3636.02

57 1997 96.60 0.00 310.69 75.01 373.68 187.24 237.20 135.54 43.82 23.75 421.54 2886.50

58 1998 166.21 7.05 473.01 149.20 310.60 128.01 299.21 182.36 120.29 60.73 527.35 3611.05

59 1999 355.61 50.46 396.43 114.20 552.86 355.49 88.43 23.22 112.89 42.14 585.51 4009.30

60 2000 126.82 0.00 213.37 30.52 204.15 28.05 33.59 0.00 5.35 0.00 58.57 401.07

61 2001 114.71 0.00 133.51 0.00 151.76 0.00 32.15 0.00 25.60 0.99 0.99 6.75

62 2002 67.78 0.00 47.12 0.00 257.74 78.37 42.44 0.00 13.01 0.00 78.37 536.63

63 2003 50.36 0.00 271.36 57.03 168.26 0.00 48.52 0.00 77.17 24.06 81.10 555.32

64 2004 82.36 0.00 125.26 0.00 138.12 0.00 36.54 0.00 35.05 5.32 5.32 36.41

65 2005 67.87 0.00 157.76 5.11 143.35 0.00 133.92 57.56 49.88 18.75 81.42 557.50

66 2006 95.00 0.00 229.07 37.70 375.99 189.40 311.13 191.36 72.75 41.44 459.90 3149.20

67 2007 224.52 20.41 207.77 27.97 270.85 90.67 277.92 166.28 130.01 63.29 368.62 2524.19

68 2008 157.23 4.99 360.87 97.95 477.47 284.70 192.09 101.48 41.79 19.58 508.69 3483.32

69 2009 25.45 0.00 269.56 56.21 167.67 0.00 166.51 82.16 83.65 35.46 173.84 1190.35

70 2010 164.96 6.76 540.79 180.19 389.45 202.04 203.71 110.26 74.85 34.45 533.70 3654.56

71 2011 385.77 57.37 183.30 16.78 244.13 65.59 145.87 66.59 8.51 2.07 208.40 1427.04

72 2012 109.12 0.00 309.20 74.33 398.72 210.74 296.43 180.26 168.10 80.81 546.14 3739.73

73 2013 268.65 30.53 518.94 170.20 340.60 156.17 146.76 67.25 282.98 118.57 542.72 3716.31

74 2014 43.16 0.00 376.38 105.04 329.91 146.14 458.66 302.75 72.08 51.97 605.89 4148.85

75 2015 571.69 99.98 221.64 34.30 150.15 0.00 215.94 119.49 9.42 7.60 261.37 1789.76

* Note

*SEP

Weighted

Average

Rainfall in

mm from

Table 4(a)

Corresponding

Runoff (mm)

Y =aX + b

*OCT

Weighted

Average

Rainfall in mm

from Table

4(a)

Corresponding Runoff

(mm)

Y =aX + b

Monsoon Yield as a summation of

Monthly Yields

Monthly Weighted Average Rainfalls have been taken from Table 4(a)

STATEMENT SHOWING MONTHLY YIELD OF MODIKUNTAVAGU PROJECT

Sl.

NoYear

*JUN

Weighted

Average

Rainfall in mm

from Table

4(a)

Corresponding

Runoff (mm)

Y =aX + b

*JUL

Weighted

Average

Rainfall in

mm from

Table 4(a)

Corresponding

Runoff (mm)

Y =aX + b

*AUG

Weighted

Average

Rainfall in mm

from Table 4(a)

Corresponding

Runoff (mm)

Y =aX + b

Tim

e(hr

)U

Hor

dina

tes(

cum

ecs)

1.71

41.

714

2.35

22.

352

2.35

24.

266

4.90

46.

854

11.2

484.

904

3.62

81.

714

0.43

60.

436

0.43

61.

702

1.70

21.

702

1.70

21.

702

1.70

81.

702

1.70

20.

436

DSR

OBA

SEFL

OW

TOTA

LFLO

W(C

UM

ECS)

00.

000.

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11.6

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6.30

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11.6

422

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233

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57.0

810

.80

0.00

67.8

711

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79.5

13

84.9

014

5.52

57.0

814

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0.00

217.

4111

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229.

054

130.

4522

3.59

145.

5278

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14.8

20.

0046

2.25

11.6

447

3.89

510

3.10

176.

7122

3.59

199.

6878

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14.8

20.

0069

3.13

11.6

470

4.77

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113.

3017

6.71

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8219

9.68

78.3

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0.00

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7111

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913.

357

45.5

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113.

3024

2.49

306.

8219

9.68

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0.00

1113

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11.6

411

24.8

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30.6

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77.9

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5.47

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4930

6.82

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03.8

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33.9

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107.

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5.47

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6.50

416.

3522

8.24

70.8

60.

0018

63.3

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1874

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1011

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19.3

733

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71.9

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7.02

155.

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9.82

639.

7358

1.90

374.

5630

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0.00

2454

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11.6

424

66.3

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6.10

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46.5

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107.

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9616

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78.1

811

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122.

804.

8010

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26.5

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71.9

719

4.10

324.

1570

6.65

1467

.30

416.

3512

0.81

10.8

00.

0034

00.5

411

.64

3412

.18

131.

402.

404.

8014

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26.5

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.57

130.

5422

3.13

453.

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59.6

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9.73

308.

0257

.08

2.75

0.00

3068

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11.6

430

80.2

914

0.00

0.00

2.40

6.59

14.3

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.58

84.4

715

0.06

311.

8674

3.49

505.

6047

3.27

145.

5214

.52

2.75

0.00

2481

.45

11.6

424

93.0

915

0.00

3.29

6.59

14.3

548

.21

97.1

020

9.73

511.

7832

4.15

374.

0522

3.59

37.0

214

.52

2.75

0.00

1867

.12

11.6

418

78.7

616

0.00

3.29

6.59

26.0

255

.42

135.

7134

4.19

223.

1323

9.81

176.

7156

.88

37.0

214

.52

10.7

20.

0013

30.0

011

.64

1341

.64

170.

003.

2911

.94

29.9

177

.45

222.

7115

0.06

165.

0711

3.30

44.9

556

.88

37.0

256

.68

10.7

20.

0097

9.99

11.6

499

1.63

180.

005.

9713

.73

41.8

112

7.10

97.1

011

1.02

77.9

928

.82

44.9

556

.88

144.

5056

.68

10.7

20.

0081

7.26

11.6

482

8.90

190.

006.

8719

.19

68.6

155

.42

71.8

352

.45

19.8

428

.82

44.9

522

2.03

144.

5056

.68

10.7

20.

0080

1.90

11.6

481

3.54

200.

009.

6031

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29.9

141

.00

33.9

413

.34

19.8

428

.82

175.

4822

2.03

144.

5056

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10.7

20.

0081

7.34

11.6

482

8.98

210.

0015

.75

13.7

322

.13

19.3

78.

6313

.34

19.8

411

2.50

175.

4822

2.03

144.

5056

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10.7

60.

0083

4.73

11.6

484

6.37

220.

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8710

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10.4

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938.

6313

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77.4

411

2.50

175.

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11.6

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5.56

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938.

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2.50

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10.7

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0087

8.03

11.6

488

9.67

240.

002.

401.

222.

664.

9333

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52.0

877

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112.

5017

5.48

222.

8114

4.50

56.6

82.

7588

9.14

11.6

490

0.78

250.

000.

611.

222.

6619

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33.7

052

.08

77.4

411

2.50

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5911

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868.

2326

0.00

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1.22

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33.7

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2.90

175.

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2.03

37.0

274

2.09

11.6

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3.73

270.

000.

614.

7710

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19.2

333

.70

52.0

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112.

5017

5.48

56.8

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3.34

11.6

455

4.98

280.

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7710

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19.2

333

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52.2

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112.

5044

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357.

6211

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369.

2629

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5630

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4

DES

IGN

FLO

OD

CA

LCU

LATI

ON

S

FIELD PHOTOGRAPHS

MODIKUNTA VAGU PROJECT SITE

PHOTOGRAPH SHOWING THE RIVER SECTION WITH ALLUVIUM

PHOTOGRAPH SHOWING THE FOLDING IN SANDSTONE ALONG THE ROAD CUTTING IN BUFFER ZONE

DOLOMITE EXPOSED ON GODAVARI RIVER BED UPSTREAM OF PROJECT SITE

PHOTOGRAPHS SHOWING THE WELLS INVENTORIED

Not

e: D

L –

Desir

able

Lim

it, P

L –

Perm

issib

le L

imit,

BDL

– B

elow

Det

ecta

ble

Lim

it

Note:�Species�identified�by�ESHCPL�team;�D=�Density,�Frq=�frequency,�Do=Dominance,�BA=�Basal�area,�RD=�Relative�density,�RFr=�Relative�frequency,�RDo=�Relative�Dominance,�IVI=�Important�Value�Index.�

�����N

ote:

�Spe

cies

�reco

rded

�by�

EHSC

PL�te

am,�N

A��N

ot�A

sses

sed.

�

ZOOPLANKTON

ZOOPLANKTON

Modiguntavagu (LIS) Socio-Economics, Telangana State

QUESTIONNAIRE

1. Personal details of respondentName of the respondent

Name of the Village

Name of the Taluk

Name of the District

Occupation

Sl. No.

Name of the person Age M/F Education Occupation Annual Income

1234567

2. Whether any of the family members is physically handicapped?

Yes No No

3. Caste :

4. Are you aware of Modiguntavagu Lift Irrigation Scheme?

Yes No

5. Whether is there any need of irrigation facilities to this region?

Yes No

If Yes, Why?

If No, Why?

MDGVLIS/SE/01 Page 1

Modiguntavagu (LIS) Socio-Economics, Telangana State

6. Land detailsTotal Land owned 1. Dry land

2. Irrigated landMode of irrigation

7. Are you willing to give your land for construction of canals?

Yes No

If Yes, What is the type of compensation expected?

If No, why?

8. Whether any of your land has been acquired earlier for any of the government projects?

Yes No

If yes, which project?

9. Whether the project will bring Socio-Economic improvement in the region?

10. Remarks (Any other information)

Name and signature of surveyor Date of survey

MDGVLIS/SE/01 Page 2

DAM BREAK ANALYSIS USING RIVER MODELING SOFTWARES

Hydrologic Engineering Centre - River Analysis System (HEC-RAS)

It's a water powered model created by the hydrologic building focus armed force corps of

architects USA. It was discharged to help water powered designers in stream channel

examination and floodplain distinguishing proof. Before long, it got to be standard stream

pressure driven investigation program, later its capacities were extended for extension, weir,

duct examination. Initially it was developed for main frame computer use, currently it can work

on PC & work stations.

The capabilities of HEC-RAS are,

� Modeling of one-dimensional steady flow.

� Modeling of unsteady flow simulation.

� Movable boundary sediment transport calculations.

� Modeling subcritical, supercritical, & mixed flow regimes

1. HEC-RAS parameters.

For stream channel geometry & water flow, its hydraulic analysis HEC-RAS uses a number of

input parameters. The locations of stream banks are identified & used to divide them as main

channel, left flood way, & right floodway for each cross section, it does so because of

difference in hydraulic parameters.

2. Data Storage & Management

Data storage is accomplished through the use of “flat” files, user input data are stored in flat

files under separate categories of projects, (plan, geometry, unsteady flow etc). Output data is

predominantly stored in separate binary files. Data can be transferred between HEC-RAS &

other programs by using the HEC-DSS. Data management is accomplished through the user

interface.

ANNEXURE-14

Steps in developing hydraulic model using HEC-RAS,

� Starting a new project.

� Entering geometric data.

� Entering flow data & boundary conditions.

� Performing the hydraulic calculations.

� Viewing & printing results.

3. Theoretical basis for one dimensional flow calculations.

3.1. Steady flow water surface profiles

“Equations for basic profile calculations,

Z1z2=elevation of main channel inverts

Y1y2=depth of water at cross sections

V1v2=average velocity (total discharge/total flow area)

G=gravity

He=head loss

3.2. Cross section subdivision for conveyance calculations

K = …………………………………………….(2)

K=conveyance for subdivision

A=flow area for subdivision

R= hydraulic radius for subdivision

3.3. Evaluation of mean kinetic energy head

“The velocity coefficient ‘a’ is computed based on the conveyance in the three flow elements

left overbank, right overbank & channels. It can also be written in terms of conveyance & area

as in the following eqn.

At= Total flow area of cross section.

Alob,Arob,Ach= flow areas of lob,rob,ch

Kt= total conveyance of cross section.

Krob,klob,kch= conveyance of lob, rob, ch.” Lob=Left of bank, Rob=Right of bank,

ch=channel.

3.4. Friction loss evaluation

Avg conveyance eqn = 2……………………..(4)

Avg friction slope eqn= )………………………….(5)

Geometric mean friction slope eqn =sf’= √sf1xsf2………………………(6)

Harmonic mean friction slope eqn

………………………………………………..(7)

3.5. Contraction & expansion loss evaluation

………………………………(8)

C = contraction or expansion coefficient

3.6. Critical depth determination

Critical depth for a cross section will be determined if any of the following conditions are

satisfied.

1) The supercritical flow regime has been specified

2) The calculation of critical depth has been requested by user.

The total energy head for a cross section is defined by,

……………………………(9)

H=total energy head

Ws= water surface elevation

= velocity head.

4. Preparation of Data for use in HEC-RAS

The HEC-RAS requires the cross sections, Manning’s roughness coefficient, channel length

and other geomorphological data. These data for the selected site are not available. However,

some of these data can be derived using Digital Elevation Model (DEM) of higher resolution

with the use of HEC-GeoRAS. In this software we can derive most of the information required

for the HEC-RAS program. The step-by-step procedure is given below,

4.1 HEC-GeoRAS Development

HEC-GeoRAS is an arrangement of instruments particularly intended to handle geospatial

information to bolster pressure driven model improvement and investigation of water surface

profile results(HEC,2005). GeoRAS helps engineers in making datasets (alluded to all in all as

RAS Layers) in ArcGIS to concentrate data vital for pressure driven displaying. The most

recent arrival of HEC-GeoRAS bolsters the extraction of rise information from DTMs in either

the TIN or framework position.

GeoRAS requires that the client have a DTM. The DTM must be anticipated into a direction

system–the coordinate arrangement of the DTM is utilized as the premise for building up each

of the RAS Layers. GeoRAS likewise requires the Stream Centerline layer and Cross-Sectional

Cut Line layer be made. The advancement of every other Ra Layersis discretionary taking into

account the information requirements for the waterway power through pressure model.

Description of RAS LAYERS

RAS Layer Description

Stream Centerline Used to identify the connectivity of the river network and

assign river stations to computation points

Cross-Sectional

Cut Lines

Used to extract elevation transects from the DTM at specified

locations and other cross-sectional properties.

Bank Lines Used in conjunction with the cut lines to identify the main

channel from overbank areas.

Flow Path

Centerlines

Used to identify the center of mass of flow in the main channel

and overbanks to compute the downstream reach lengths

between cross sections.

4.2 TIN creation

Tin is defining the layer of earth which resulting from field surveying and take the deferent

elevation to topographic of earth by using the surveying instrument, after that is fixed by (GIS)

program. A multi-step procedure was used to create a TIN from multiple sources of elevation

data. The following steps were used,

� Generate a TIN in Arc GIS using the survey data exclusively (no DEM data for the

flood plain). The TIN generation is an automated GIS process that generates a

preliminary TIN whose exclusive purpose is to incorporate the survey data into a surface

for extraction into HEC-RAS.

� Digitize the centerline and bank lines of the river from satellite imagery. This step adds

additional information about river alignment and meandering that is not available in

the reaches between surveyed cross-sections.

� Delineate cross sections in GeoRAS/ArcGIS that correspond to surveyed cross section

locations, but that are confined within the bank-lines drawn instep2

� Extract the cross sections, bank lines, and river centerline to RAS. This step provides

HEC-RAS with all of the original cross-section data in a geo-referenced form.

� Interpolate additional cross sections at 600-meter spacing between surveyed cross

sections, following the river centerline, and export the cross sections to GeoRAS/

ArcGIS.

� Delineate break lines in ArcGIS at the centerline and at previously defined bank lines

with elevations defined by surveyed and interpolated cross-sections.

4.3 Creating the require layer under Hec-Geo Ras

The Stream Centerline layer is used to identify the connectivity of the river system. It is

created in the downstream direction and is used to assign river stations to the cross-sections,

bridges, and other structures to order computational nodes in the HEC-RAS model. The

Cross-Sectional Cut Lines layer is the principal data constructed using HEC-GeoRAS. Cut

lines are digitized across the flood plain area to capture the profile of the land surface. Cross-

sections should be digitized perpendicular to the path of flow in the channel and overbank are

as to be consistent with one- dimensional flow characteristics. Having created the bank lines

and flow path centerlines prior to laying out cut line locations is advantageous. Once the RAS

Layers have been created, GeoRAS tools and menus are available to assign and populate

attributed at Lastly, the data are written out to the HEC-RAS geo-spatial data exchange format

and can be imported into HEC-RAS.

The Triangulated Irregular Network (TIN) has been used to derive the information within the

Hec-Georas environment. The layers developed using the TIN is shown below,

Digital Elevation Model (DEM)

Triangulated Irregular Network (TIN)

4.4 HEC-RAS Model Development:

HEC-RAS is a one-dimensional river hydraulics model used for steady-flow and unsteady-

flow water surface profile computations though a network of open channels (HEC,2002).

Because HEC-RAS solves the full Saint-Venant equations, it is well suited for computing

the flood wave propagation resulting from a dam failure scenario.

Initial model development may be performed using HEC-GeoRAS and using an HEC-

RAS option to import the GIS data. At a minimum, the data import should establish the

river/reach schematic and the description of cross-sections. The river hydraulics model will

need additional cross-section in formation, hydraulic structures data, flow data, and

boundary conditions prior to simulation. This section will focus on just a few of the more

important data considerations.

4.5 Channel Data:

If the cross-sectional data came from a lower solution terrain model the channel data will not

be represented in the cross-section. For a large flood wave resulting from a dam break, the

channel data may not be significant. The importance of the channel portion of the total cross-

sectional conveyance will need to be evaluated: if the channel conveyance is rather small

compared with the total conveyance, for instance, the peak stage of the flood wave may not

be significantly affected. To perform the dam breach analysis, however, RAS will need a

channel for the low-flow portion of the simulation.

If channel data are available from previous hydraulic studies, HEC-RAS provides the

capability to merge data from two different geometry files. Using the channel merge

capabilities in RAS, channel data or overbank data can be merged with an existing data set.

If channel data is not available, it can be estimated from field surveys and topographic

maps. A shape may be estimated for uniform sections of channel and added to the overbank

data. HEC-RAS provides channel modification tools for quickly adding a trapezoidal

channel to cross-sections along a given river reach., the data extracted from the terrain

model are horizontal in the main channel reflecting the elevation of the water surface during

data capture. A trapezoidal channel is added based on an approximation or survey of water

depth, top width, and side-slopes.

4.6 Dam Break Modeling

� Generally, dam break modeling can be carried out by either i) scaled physical

hydraulic models, or ii) mathematical simulation using computer. A modern tool to

deal with this problem is the mathematical model, which is most cost effective and

reasonably solves the governing flow equations of continuity and momentum by

computer simulation.

� Mathematical modeling of dam breach floods can be carried out by either one

dimensional analysis or two-dimensional analysis. In one dimensional analysis, the

information about the magnitude of flood, i.e., discharge and water levels, variation

of these with time and velocity of flow through breach can be had in the direction of

flow. In the case of two-dimensional analysis, the additional information about the

inundated area, variation of surface elevation and velocities in two dimensions can

also be assessed.

� One dimensional analysis is generally accepted, when valley is long and narrow and

the flood wave characteristics over a large distance from the dam are of main interest.

On the other hand, when the valley widens considerably downstream of dam and large

area is likely to be flooded, two-dimensional analysis is necessary.

5. Results: Analysis and discussion

The study has been carried out for two flow conditions such as Steady and Un-steady flow, i.e.,

by using the return period flood and PMF generated for the basin respectively.

5.1 Data generation using the DEM and HEC-GEORAS

The modeling of dam breach requires the data such as; river cross sections, longitudinal

section of the river, and other river hydraulic characteristics. However, there were no data

available with regard to the river cross-section and longitudinal section of the river. In order

to obtain the details of river cross section and other details, an additional program called HEC-

GeoRAS has been used. This software basically derives all the required information to setup

the HEC-RAS model using the Digital Elevation Model (DEM). To facilitate such work, a

DEM generated BHUVAN was used (32 m resolution).

5.2 Procedure to derive the required information by HEC-GeoRAS.

The HEC-GeoRAS uses the TIN format of the DEM to derive the information. Therefore, the

DEM of Modikuntavagu Dam was converted into TIN format and is used to derive the required

data as explained below,

Digitizing River attributes in HEC-GEORAS.

� Add Data to ARC map, our study area in TIN format.

� Go to Ras geometry, create RAS layers- (Stream center line, Bank lines, Flow path

center line, XS cut lines).

� Shape files for all four to be created & digitize later one after the other. Assign left &

right orientation with respect to flow direction to flow paths.

� Enter river ID.Values of each shapefiles can be checked in attribute tables.

� Export RAS data (Ras layers on tin created in HECGEORAS) from RAS geometry.

5.3 Un-Steady flow Modeling

In the present study, the un-steady flow modeling has been carried out using the PMF generated

for the catchment. In this case, we have studied the two cases, (i) Reservoir empty and (ii)

Reservoir full conditions. The dam and the reservoir as represented in the HEC-RAS.

However, before we simulate the flood inundation for these conditions, it has to be

conceptualized how the dam would be breaching and the time taken for breaching after the

PMF enters into the reservoir. The conceptualization is done by providing the details of dam

breach and the boundary conditions.

Dam Breach Parameters

The assumptions regarding dam breach parameters are critical for dam break modelling. Thus,

reasonable values for the breach size and development time along with feasible breach

geometry are needed to make a realistic estimate of the outflow hydrographs. Nonetheless,

determining the size and growth rate for breaches is an inexact science while they are key

parameters in dam break models. Therefore, the estimation of the breach parameters yield a

significant source of uncertainty in the results and in turn downstream inundation extends.

Boundary Conditions

The assumptions regarding boundary conditions are also critical for dam break modelling as

they could directly affect extend of downstream floodwaters. Initial flows and water level

values, input hydrographs, and downstream boundary conditions, were specified to initialize

and run the dam break model. These boundary conditions must be properly selected and they

must best represent the site conditions. In this study the following conditions were considered;

(i) the inflow hydrographs for the upstream boundary; four extreme input hydrographs of

Probable Maximum Flood (PMF) flood was considered for the flood simulations; (ii)

downstream boundary conditions were established as the normal depth at the last cross-section

on the river.

Case (i): When Reservoir Empty

In this case, it is assumed that, the reservoir empty (no live storage) and PMF is approaching

the Dam. In order to simulate the situation. The HEC-RAS requires to be given the various

details of the DAM and EAC. This information is fed to the software and the program was

executed for simulating the flood situation.

Case (ii) Reservoir Full

In this case, it is assumed that, the reservoir is completely filled and PMF is approaching the

reservoir. As it is conceptualized that, the PMF will be routed on the first instance by using the

reservoir pool method and once the dam is breached, using the Muskingum method.

5.4 Flood Inundation Mapping

The flood plain in the study area for different scenarios like steady flow, unsteady flow, steady

flow with dam, unsteady flow with dam etc, is superimposed on IDW way of interpolation to

know water surface elevations (obtained after simulation in HEC-RAS) in the flood plain

region. Digitize the water surface elevations on similar elevations on contour format of study

area, create a polygon by joining the digitized water surface elevation, the area of polygon itself

will the area of inundation, same process to be carried for all scenarios to find area of

inundation.

CONCLUSION

Various techniques and assumptions are available for developing the key components of dam

breach model in HEC-RAS. The reservoir routing method, breach parameters, model used to

develop the breach hydrograph, inclusion or exclusion of bridges, method of modeling storage

in tributaries, and flow level in the receiving stream are just some of the factors that must be

considered in the analysis. Each of these affects the results to varying degrees and the impact

on one model may be different than on another.

In the present study, an attempt was made to simulate the flood inundation due to the breach of

the Modikuntavagu dam. The simulations were done for various scenarios to understand the

dynamics of the dam breach and to minimize the uncertainty in mapping the flood inundation.

The results obtained show that, the conceptualization with which the model was set-up looked

appropriate to the condition prevailing at the site. However, looking at the results obtained and

the discussion, following are some of the major conclusions drawn are;

(1) The HEC-RAS provides the flood profile for the worst flood intensity. This profile will

facilitate to adopt appropriate flood disaster mitigation measures.

(2) The flood profiles for different flood intensities with different return periods can be

plotted at any given cross section of river. Also, such flood profile can be plotted for

entire length of river reach.

(3) The major conclusion drawn from steady and unsteady flow analysis without

dam, Inundated area for steady flow state is 20 % more than unsteady flow.

Whereas for steady & unsteady flow analysis when dam breaks, area of

inundation for steady flow state is 8 % more than unsteady flow case.

( 4 ) The study also made the assessment of flood hazards with relation to the (100,

500, 1000 year) return period of floods and their water depth. The relationship between

the flood area and discharge indicates that there is a medium rate of increase of the

flood area with the increase in discharge.

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n of

Des

ign

Floo

d

0

500

1000

1500

2000

2500

3000

3500

4000

01

23

45

67

89

1011

1213

1415

1617

1819

2021

2223

2425

2627

2829

3031

3233

3435

3637

3839

Total Flow in Cumecs

Tim

e (h

r)

Des

ign

Floo

d

Vill

ages

falls

unde

r th

e In

unda

ted

area

of D

owns

trea

m o

f Mod

ikun

tava

gu D

am

�T

ekula

gudem

Z

�T

ekula

gudem

Chal

k –

II

�K

rish

nap

ura

ng

�P

eddag

angar

am Z

�P

eruru

G

�D

har

mav

aram

�P

eruru

Z

�A

yyav

arip

eta

G