IMPACT Project Breach Modeling Tests

Dam Failures Increasing (?) Worldwide

Some Recent Headlines

March 23, 1999 Chinese Dams Damned                        By Duncan Hewitt (BBC) in Beijing Thousands of Chinese dams have been described as "time bombs" by Chinese officials. They said more than one-third of the country's estimated 85,000 dams are defective and need urgent repairs.

Aug. 21, 2002Dam Bursts in Central India, 25 Feared Dead BHOPAL, India (Reuters) -- A dam burst under the pressure of heavy monsoon rains in central India on Wednesday, washing away at least 25 people, officials said.

August 16, 2002Dams Burst in Mexico, Killing 11By THE ASSOCIATED PRESSVILLA DE REYES, Mexico (AP) -- Heavy rains burst two dams and sent a wave of flood waters roaring over villages in central Mexico, where authorities said at least 11 people were killed -- including a 6-month-old baby.

Tuesday, 4 June, 2002Syrian Dam CollapsesDAMASCUS, Syria (BBC) -- Villages have been flooded in northern Syria after a dam collapsed. The state-run Syrian Arab News Agency (Sana) reported widespread damage and heavy casualties around the Zeyzoun Dam, near the town of Hama, about 350 kilometres (220 miles) north of Damascus.

Breach Model Tests

• A priori simulation of failure of two large-scale experimental earthen embankments from erosion by overtopping flows

• Two-dimensional depth-averaged flow and sediment transport model that models breach development and the resulting flood wave.

Governing Equations

0)](),([

QUGUFU

t

k

byb

bxb

kkk S

y

zgh

x

zgh

qC

ghh

qh

qqq

qCh

qq

ghh

qq

hC

q

q

h

1

10

2

12

1

2

222

21

2

1

21

221

1

2

1 QGFU

Sediment Transport (General)

)(

)(

**

**

depositionCCforCCw

erosionCCforCCwKp

S

kkkksk

kkkkskekk

k

6/1

*

5.1exp1

1

h

T

u

w

h

T

h

TK

askaa

ek

Total Load Equations

• Engelund-Hansen• Laursen• Bagnold (1956)• Yang (sand and

gravel)• Meyer-Peter and

Mueller• Others…

k

kb St

z)1(

Bed Composition Accounting

• Conceptual model of Bennett and Nordin (1977)

• Three layers• Active layer always• Deposition layer

sometimes• Armoring can occur

A c t i v e L a y e r A c t i v e L a y e r

D e p o s i t i o nL a y e r

O r i g i n a lB e d

M a t e r i a l

O r i g i n a lB e d

M a t e r i a l

T a

T d

T o

Embankment Erosion

cbs

dkk

KpS

Soil textural class

Detachment rate

constant, Kd

Detachment threshold bed shear

stress

(Kg/s/m2/Pa) (Pa)

Clay loam 0.0048 4.7

Loam 0.0085 3.3

Sand 0.0250 2.1

Sandy loam 0.0100 2.5

Silt loam 0.0120 3.5

Clay 0.0089 2.9

Silty clay 0.0120 4.8

Silty clay loam

0.0053 3.2

Soil Texture Classes

Finite Volume Formulation

0)()~

,~

(1

advi

jjRL

i

ni

ni t

A

tUQUUFTUU 1

0

0

)()(2

10

)~

()~

( bLbRRL zzhhgUFUF

k

by

bx

S

1

10

Q

Field Test #1 Mesh

Field Test #1 Mesh

Field Test #1 Embankment

• Homogeneous (maximum cohesive) soils:

– Clay = 25%– Silt = 60%– Sand = 15%

• Embankment:– Height = 6.0 m– Length = 36 m– Slope = 2:1 (horz:vert)

upstream and down

• Crest:– Elevation = 370.81 m– Width = 2.0 m

Field Test #1 at 1:00 h

Field Test #1 at 2:00 h

Field Test #1 at 2:30 h

Field Test #1 at 4:00 h

Field Test #1 Crest Profile

Field Test #1 - Dam Crest Profile

364

366

368

370

372

0 10 20 30 40

Crest Distance (m)

Ele

va

tio

n (

m)

0:00

1:00

1:30

2:00

3:00

6:00

Field Test #1Embankment Transect

Embankment Transect at Notch

364

365

366

367

368

369

370

371

0 5 10 15 20 25

Distance (m)

Ele

vati

on

(m

)

0:00

0:30

1:00

1:30

2:00

3:00

4:00

5:00

Field Test #1 Breach Hydrograph

Field Test #1 - Dam Breach Hydrograph

0

20

40

60

80

100

120

0 1 2 3 4 5 6

Time (h)

Flo

w R

ate

(m3 /s

)

• Homogeneous (minimum cohesive) soils:

– Clay and silt = 2%– Sand = 42%– Gravel = 56%

• Embankment:– Height = 5.0 m– Length = 36 m– Slope = 1.7:1

(horz:vert) upstream and downstream

• Crest:– Elevation = 369.81 m– Width = 2.0 m

Field Test #2 Embankment

Field Test #2 at 0:30 h

Bed elevation (m) : 0.500

364.00

364.80

365.60

366.40

367.20

368.00

368.80

369.60

370.40

371.20

372.00

Field Test #2 at 1:00 h

Bed elevation (m) : 1.000

364.00

364.80

365.60

366.40

367.20

368.00

368.80

369.60

370.40

371.20

372.00

Field Test #2 at 1:30 h

Bed elevation (m) : 1.500

364.00

364.80

365.60

366.40

367.20

368.00

368.80

369.60

370.40

371.20

372.00

Field Test #2 at 2:00 h

Bed elevation (m) : 2.000

364.00

364.80

365.60

366.40

367.20

368.00

368.80

369.60

370.40

371.20

372.00

Field Test #2 at 6:00 h

Bed elevation (m) : 6.000

364.00

364.80

365.60

366.40

367.20

368.00

368.80

369.60

370.40

371.20

372.00

F ie ld T e s t # 2 - D a m C r e s t P r o f ile

3 6 4

3 6 6

3 6 8

3 7 0

3 7 2

0 1 0 2 0 3 0 4 0

C r e s t D i s ta n c e (m )

Ele

va

tio

n (

m)

0 : 0 0

0 : 3 0

1 : 0 0

1 : 3 0

2 : 0 0

3 : 0 0

6 : 0 0

Field Test #2 Crest Profile

E m b a n k m e n t T ra n se c t a t N o tc h

3 6 4

3 6 5

3 6 6

3 6 7

3 6 8

3 6 9

3 7 0

0 5 1 0 1 5 2 0 2 5

D is ta n c e (m )

Ele

vati

on

(m

) 0 :0 0

0 :1 5

0 :3 0

1 :0 0

1 :3 0

2 :0 0

Field Test #2Embankment Transect

Field Test #1 Breach Hydrograph

Field Test #2 - Dam Breach Hydrograph

0

10

20

30

40

50

60

0 1 2 3 4 5 6

Tim e (h)

Flo

w R

ate

(m3 /s

)