Types of Stilling Basins

1. Types of Hydraulic Jump
For hydraulic jump to occur, upstream flow must be
supercritical (F > 1)
• Type of jump depends on value of F1

2. Types of Hydraulic Jump

3. Hydraulic jumps used downstream of gates &
other structures to dissipate energy & avoid
damage downstream
Best for design: “Steady Jump” 4.5 < F < 9.0
Avoid “Oscillating Jump” 2.5 < F < 4.5

4. Stilling Basins
• Use stilling basin to initiate jump
• Allows dissipation of energy
within a structure that will
minimize damage
• Baffle blocks used to make jump
position more stable

5. Stilling Basins: Design Considerations
Length of jump Governs length of stilling basin
Approximately 6 y2 for 4.5 < F1 < 13
Surface profile of jump
– Governs height of sidewalls of
– Dictates pressure on floor of basin
– Depends on y1 and F1
• Control of jump
(1) Chute Blocks (2) Baffle Blocks (3) End Sill
Components used to initiate jump, stabilize jump, &
make basin as short as possible

6. Control of jump by baffle piers

7. Control of jump by baffle piers

8. Stilling Basin Design
• General stilling basin designs from USBR–
Types I II III and IV based on F1
• Type I: 1.7 < F1 < 2.5
Weak jump
No special structures needed
4 . 5 < F < 9 for best design
Type II or III stilling basin
Type II 4.5 < F1

9. TYPE III 4.5 < F1
Use for incoming velocity V1 < 60 ft/s

10. Use for incoming velocity V1 > 60 ft/s
Dentated sill, no baffle blocks TYPE II 4.5 < F1

11. • Type IV 2.5 < F1 < 4.5
• Oscillating Jump, unstable
• No baffle blocks because of wave action