Problems

  1. As part of an industrial development, a stream crossing must be constructed immediately upstream of river mile 9.33 in a given channel reach, which is shown schematically in the figure.

    2. Click here for larger image

    English Units - Cross-sectional geometry for the channel reach without the proposed stream crossing is provided in the file Prob7_1eng.g01 on the CD-ROM accompanying this text. The channel design discharge can be taken as 2,200 cfs along its entire length. The flow regime is subcritical, and normal depth can be assumed as the reach's downstream boundary (R.M. 5.0), where the channel slope is 0.0023. For the existing condition (no stream crossing), answer the following questions.

    1. What is the computed water surface elevation at river mile 6.0?
    2. What is the average main channel velocity at river mile 7.0?
    3. How much frictional head loss occurs between sections 7.0 and 8.0?
    4. What are the left overbank, main channel, and right overbank conveyances at river mile 9.33?
    5. What is the energy grade elevation at river mile 9.33?
    6. What is the energy correction factor (a) at river mile 5.0?

      7. SI Units - Cross-sectional geometry for the channel reach without the proposed stream crossing is provided in the file Prob7_1si.g01 on the CD-ROM accompanying this text. The channel design discharge can be taken as 62.3 m3/s along its entire length. The flow regime is subcritical, and normal depth can be assumed as the reach's downstream boundary (R.M. 5.0), where the channel slope is 0.0023. For the existing condition (no stream crossing), answer the following questions.

    7. What is the computed water surface elevation at river station 6.0?
    8. What is the average main channel velocity at river station 7.0?
    9. How much frictional head loss occurs between sections 7.0 and 8.0?
    10. What are the left overbank, main channel, and right overbank conveyances at river station 9.33?
    11. What is the energy grade elevation at river station 9.33?
    12. What is the energy correction factor (a) at river station 5.0?
  2. English Units - The stream crossing will be constructed immediately (assume 1 ft) upstream of river mile 9.33. The table provided contains data on the proposed vertical alignment of the 40 ft wide roadway crossing the stream. Assume that the cross-section immediately upstream of the crossing has the same geometry as river mile 9.33.

    3. Station, ft
    Roadway Elevation, ft
    Station, ft
    Roadway Elevation, ft
    Station, ft
    Roadway Elevation, ft
    -1+80
    937.6
    0+20
    935.1
    2+20
    935.8
    -1+55
    937.3
    0+45
    934.9
    2+45
    936.0
    -1+30
    937.0
    0+70
    934.9
    2+70
    936.1
    -1+05
    936.7
    0+95
    935.0
    2+95
    936.3
    -0+80
    936.3
    1+20
    935.2
    3+20
    936.4
    -0+55
    936.0
    1+45
    935.3
    3+45
    936.3
    -0+30
    935.7
    1+70
    935.5
    3+70
    936.8
    -0+5
    935.3
    1+95
    935.6
    		   

    Add any cross-sections necessary to model a culvert crossing. Assume that the topography is such that interpolation feature of HEC-RAS can be used to develop any additional geometry. Add the deck/roadway data to the stream system, insert two 10 ft x 8 ft box culverts at the crossing, and add ineffective flow areas as needed. The culverts will have 45-degree flared wingwalls with no bevels or chamfers. Answer the following questions.

    1. What is the water surface elevation at river mile 9.33?
    2. How was this water level determined?
    3. What is the energy grade elevation immediately upstream of the culvert group?
    4. Is the culvert operating under inlet control or outlet control?
    5. What is the flow velocity in the culverts at the upstream and downstream ends?
    6. Do two 10 ft x 8 ft box culverts represent an acceptable design if the water surface elevation in the channel for the design flow may not increase by more than 1 ft?

      7. SI Units - The stream crossing will be constructed immediately (assume 0.3 m) upstream of river mile 9.33. The table provided contains data on the proposed vertical alignment of the 12.2 m wide roadway crossing the stream. Assume that the cross-section immediately upstream of the crossing has the same geometry as river mile 9.33.

      Station, m
      Roadway Elevation, m
      Station, m
      Roadway Elevation, m
      Station, m
      Roadway Elevation, m
      -54.9
      285.78
      6.1
      285.02
      67.1
      285.23
      -47.2
      285.69
      13.7
      284.96
      74.7
      285.29
      -39.6
      285.60
      21.3
      284.96
      82.3
      285.32
      -32.0
      285.51
      29.0
      284.99
      89.9
      285.38
      -24.4
      285.38
      36.6
      285.05
      97.5
      285.42
      -16.8
      285.29
      44.2
      285.08
      105.2
      285.48
      -9.1
      285.20
      51.8
      285.14
      112.8
      285.54
      -1.5
      285.08
      59.4
      285.17
      		   

    7. What is the water surface elevation at river mile 9.33?
    8. How was this water level determined?
    9. What is the energy grade elevation immediately upstream of the culvert group?
    10. Is the culvert operating under inlet control or outlet control?
    11. What is the flow velocity in the culverts at the upstream and downstream ends?
    12. Do two 3.0 m x 2.4 m box culverts represent an acceptable design if the water surface elevation in the channel for the design flow may not increase by more than 0.3 m?
  3. Design a culvert system that will pass the design discharge without increasing water levels by more than 1.0 ft (0.3 m).
    1. Describe your proposed design.
    2. What is the resulting water surface elevation at river mile 10.0?
    3. What is the increased amount from the existing condition?
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