Dam removal sediment transport using hecras

A HECRAS Sediment Transport Computational Study for Dam Removal

12/16/11Bishes Rayamajhi

Instructor: Dr. Hans Tritico

Goal of the Project

• To compute the additional sediment volume transported after the removal of a low head dam.

Project Area

• 33.518 river length of Mahoning River encompassing two Ohio counties; Trumbull and Mahoning meeting the Pennsylvania – Ohio state border at 11.838 RM.

• Crescent St Dam located at 23.023 RM to be removed under my project scope.

HECRAS parameters used:

• Transport Function – England and Hasen• Computational interval – 1 hour• Computational time period – Jan 1, 10 to Dec

31, 10• Grain size distribution – Normal

RESULTS

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00

-1000.00

-800.00

-600.00

-400.00

-200.00

0.00

200.00

400.00

Time (days)

∆ M

ass

Out

(ton

s)

Change in mass outflow before and after removal at 23.073 RM

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00

-500000

-450000

-400000

-350000

-300000

-250000

-200000

-150000

-100000

-50000

0

BeforeAfter

Time (days)

Long

itudi

nal C

umul

ative

Mas

s Cha

nge

(ton

s)

Longitudinal Cumulative mass changes before and after removal at 23.073 RM

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

Time (days)

∆ M

ass

Bed

Cha

nge

Cum

ulat

ive

(ton

s)

Change in cumulative mass bed change before and after removal at 23.073 RM

0 500 1000 1500 2000 2500 3000790

800

810

820

830

840

850

860

870

880

890

1-Jan31-Dec

Station (ft)

Elev

ation

(ft)

Bed elevation change for RM 23.073 after dam removal

CONCLUSION

• 230,000 tons of sediment will be transported towards the dam’s downstream by the end of the year.

• This additional sediment will be accumulated in the upstream of Mahoning Ave Dam.

• Increased in sediment movement observed for high flow conditions.

• Pre-dam removal sediment transport studies will help the engineers and planners in solving the sediment transport management problem due to the removal.