LAB 2 Spillway

Labratory Setup
VIDEO: Spillway-Placing Baffle Blocks
VIDEO: Position Hydraulic Jump
Scour and Scour Protection

Getting Started

Safety Considerations


  • Closed toed shoes are required in the Hydrotechnical Lab
  • Safety glasses are required in the Hydrotechnical lab
  • Incorrect use of the apparatus may cause water hammer which may 
burst the pipes
  • Never leave power connections (e.g. electrical plugs) on the ground in case of flooding
  • Do not let water flow exceed 1 ft3/sec as the water may overflow.
  • Do not run the power cord under the flume as water leaks out.

Laboratory Setup

Spillway Setup

Spillway Setup



    1. Turn on the spillway pump switch on the west wall.
    2. Open the inlet value to fill the reservoir of the spillway and the box just upstream of the v-notch weir just up to the base of the v-notch weir. Then close the inlet valve.


    1. Measure the zero value heights for the reservoir (water level just touches the top of the spillway) and the v-notch weir. The acoustic sensor will also measure the reservoir height.
    2. Install all baffle blocks in a symmetric pattern downstream of the toe of the spillway.

      Baffle Block Setup

      Baffle Block Setup

      VIDEO: Spillway-Placing Baffle Blocks

      The following video demonstrates how to setup the baffle blocks.

      CIVL 316 Lab2 Video 1: Spillway – Placing Baffle Blocks

    3. Adjust the inlet valve until the acoustic flow meter reads 0.5cfs.
      Flow Meter


  1. Create a hydraulic jump at the toe of the spillway by adjusting the downstream sluice gate. Position the jump just after the baffle blocks and before the metal part of the flume so that hydraulic jump is visible. Note that the position of the jump is very sensitive to the sluice gate position, so be patient and only make small adjustments.The following video demonstrates how to position the hydraulic jump by adjusting the sluice gate.

    VIDEO: Position Hydraulic Jump

    CIVL 316 Lab2 Video 2: Spillway – Position Hydraulic Jump

  2. Measure the water depth downstream of the hydraulic jump using a ruler or the ultrasonic meter.
  3. Remove all baffle blocks without turning off the flow and adjust the weir, to maintain the position of hydraulic jump.
  4. Measure the water levels:
    1. On the reservoir
    2. Just upstream of the jump
    3. Downstream of the jump
    4. Measure the total head just upstream of the jump using the pitot tube
  5. After you are done with these measurements, adjust the supply valve to get a new flow rate of 0.75 and 1.0 cfs. Then repeat the experiment from step 6.


Scour and Scour Protection

  1. Turn off the flow and remove the scour hole cover under subcritical flow. Otherwise, you will have a hard time removing the plate. Place some fine gravel in the scour hole so that it is level with the spillway apron.
  2. Set flow to 0.5  ft3/sec. by adjusting the inlet valve.
  3. Raise the sluice gate to ensure supercritical flow over the scour hole. Note that supercritical flow occurs down the face of the spillway and upstream of the hydraulic jump.
  4. Sketch the scour.
  5. After observing the scour in supercritical flow, lower the gate to get a subcritical flow occurring over it. Sketch the scour.
  6. Add more sand to the scour hole from the downstream box using the plastic scooper.