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, 2002 Dam 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, 2002 Dams Burst in Mexico, Killing 11 By THE ASSOCIATED PRESS VILLA 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, 2002 Syrian Dam Collapses DAMASCUS, 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

Sediment Transport (General)

Total Load Equations Engelund-Hansen Laursen Bagnold (1956) Yang (sand and gravel) Meyer-Peter and Mueller Others…

Bed Composition Accounting Conceptual model of Bennett and Nordin (1977) Three layers Active layer always Deposition layer sometimes Armoring can occur

Embankment Erosion Soil textural class Detachment rate constant, K d Detachment threshold bed shear stress (Kg/s/m 2 /Pa)(Pa) Clay loam Loam Sand Sandy loam Silt loam Clay Silty clay Silty clay loam

Soil Texture Classes

Finite Volume Formulation

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 = 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 Embankment Transect

Field Test #1 Breach Hydrograph

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 = m –Width = 2.0 m Field Test #2 Embankment

Field Test #2 at 0:30 h

Field Test #2 at 1:00 h

Field Test #2 at 1:30 h

Field Test #2 at 2:00 h

Field Test #2 at 6:00 h

Field Test #2 Crest Profile

Field Test #2 Embankment Transect

Field Test #1 Breach Hydrograph