1. Assoc. Prof. Dr. Tarkan Erdik
Diversion Weirs
Assoc. Prof. Dr. Tarkan Erdik
Department of Civil Engineering, I.T.U

2. DIVERSION WEIRS Definition and Classification
 Built to raise level & divert water for the purposes of irrigation, hydropower, etc.
The followings should be satisfied in designing any diversion weir:
desired amount of water at any time
no sediments entering into the water intake
minimum head losses at the water intake
easy flushing of accumulated objects at the water intake

6. Differences btw Dams and Diversion weirs
Built on whole valley
Built on river bed
To store water
To rise water
Can regulate the flow regime
Can not regulate the flow regime
Can be built certain locations on stream espc. Upstream locations
Can be built everywhere on stream
Dam failure leads catastrophic damages
Failure causes comparatively little damages
Designed according to static forces
Designed according to static and dynamic forces
Have large environmental effects
Have small environmental efects

7. Classification can be made as:
ACCORDING TO MAGNITUDE OF Q100
- Small (Q100 < 100 m3/s)
Intermediate (100 m3/s < Q100 < 500 m3/s)
- Large (Q100 > 500 m3/s)
ACCORDING TO STRUCTURAL DESIGN
Diversion weir with spillway
Gated diversion weir
Gated spillways control the upstream of water level for relatively mild sloped rivers in wide plains. However, continous operation of gates may cause some operational problems due to dynamic impacts.

8. ACCORDING TO ORIENTATION OF INTAKE
with sidewise (lateral) intake
with frontal intake
with drop (bottom) intake
Diversion Weirs with Sidewise Intakes
 suitable for plain rivers having uniform concentration vertically.
 In Turkey, the 90% of weirs is of this type.
 similar construction to dams.

9. Plan view of diversion weir

10. A diversion canal is designed with a capacity of Q5 aor Q10
A diversion canal is designed with a capacity of Q5 aor Q10. Upon completion of the construction cofferdams are demolished.

11. STRUCTURAL COMPONENTS:
1) Sidewalls: Boundaries of structures / Acting like retaining wall / The river flow is confined with them.
Spillway: Collects, raises and diverts flow to the intake
Sluiceway: Component like culvert. Equipped with vertical gate. When sediment is deposited up to the certain elevation it is opened and sediment is discharged.Prevents the deposition of sediment in front of intake (with square cross section with 2.5x2.5 m, with bottom slope ranging 1/20 to 1/50)
Guiding wall: Deflects sediment towards the sluiceway. Optimum orientation can be determined through hydraulic model tests.
Upstream blanket: Retards the seepage path. (4mx4m concrete blocks with 30cm thickness). Sheet pile is usually driven at the end of the blanket to keep it safely and to further increase the seepage path.

12. Energy dissipating basin: Prevents the scour of the river bed
Energy dissipating basin: Prevents the scour of the river bed. It is made of concrete blocks with compressive strength 250kgf/cm2 in approximately 5m in lengths. The thickness is determined such that slap is safe against uplift.
Riprap: Follows “energy dissipating basin” to protect the river bed (stones with 75 cm thick & 10 m long).
Fish passage: Provides the passage of fish.
Raft passage: Only constructed if log transportation is required.
Intake: Takes the required discharge & transmits it to the main channel.

13. Structural components of intake:
Submerged curtain: to prevent the entrainment of floating objects such as ice, logs, ets. It extends to a minimum of cm depth from the top of the intake.
Screens: racks at the entrance of intake (in front of the vertical gate) to retard floating objects and coarse sediment
Settling basin: to ensure the settlement of sediment grains up to certain size. A long and wide settling basin is effective in capturing the sediment.
Flushing canal: located at the end of the settling basin & used to discharge sediment deposited in the settling basin. The flushing facility is usually a circular conduit having a minimum diameter of 60cm and a sufficient slope for self-cleansing.
Transition: connects the rectangular settling basin to a trapezoidal irrigation channel

14. Screens

15. IN RIVER BENDS:
Sediment is deposited at the inner edge but erosion occurs at the outer edge due to centrifugal force.
=> Water Intake – located in the second half of the outer edge.
For sediment control facilities “Haberman’s model”

25. The field measurements of Lane indicated that the permeability of an alluvial bed in the horizontal direction is about three times the permeability in the vertical direction