Short Answer:

Canal falls are structures built in canals to lower the water level where there is a steep slope or difference in ground level. They help in safely dropping the water from a higher to a lower level without causing erosion. These falls maintain a steady flow of water and protect the canal bed.

There are different types of canal falls used in hydraulic engineering, such as vertical drop fall, glacis fall, stepped fall, notch fall, and siphon fall. The choice of fall depends on the site conditions, discharge, and soil type to ensure efficient water movement and safety.

Detailed Explanation:

Types of Canal Falls Used in Hydraulic Engineering

Canal falls are important structures used in irrigation channels to control and manage water when the natural ground level drops. If water flows freely over a steep slope, it can cause high velocity and erosion, damaging the canal. To avoid this, canal falls are constructed to drop water in a controlled way.

These falls are placed at regular intervals in sloping areas. Their main purpose is to dissipate the extra energy of flowing water, prevent scouring, and maintain a constant slope for smooth canal operation. Different types of canal falls are used in hydraulic engineering based on discharge, flow conditions, and topography.

1. Vertical Drop Fall
   Also known as a simple drop fall, this type allows water to fall freely from a high level to a lower level.

• Suitable for small discharges.
• Easy and economical to build.
• Water falls vertically into a stilling basin.
• Energy is absorbed in the basin, preventing erosion.

2. Glacis Fall
   In this fall, water flows over a sloped surface (called glacis) instead of falling vertically.

• Suitable for medium to high discharges.
• Smooth transition reduces erosion.
• Commonly used due to better energy dissipation.
• Curved or straight glacis designs are used.

3. Stepped Fall
   This type has a series of small drops or steps, so water flows down in stages.

• Suitable for very steep slopes.
• Reduces energy gradually.
• Less chance of erosion and better control.
• Used in hilly areas or sharp ground drops.

4. Notch Fall
   In this design, water flows through one or more notches in a wall.

• Used where accurate discharge control is needed.
• Notches can be rectangular or trapezoidal.
• Common in distributaries and minor canals.

5. Siphon Fall
   This fall carries water through a closed pipe or barrel and discharges it at a lower level.

• Works like a siphon, useful when space is limited.
• Helps in crossing obstacles or roads.
• Needs careful design to avoid air lock and blockage.

Use and Importance in Canal System

Canal falls are not only for controlling level differences, but also:

• To prevent damage due to high flow velocity.
• To control the water level upstream for proper irrigation.
• To avoid scouring of canal bed and banks.
• To maintain a regular and safe slope in uneven terrains.

Proper design of the fall type ensures long-term performance and protection of the canal. Often, energy-dissipating devices like stilling basins, baffle walls, or aprons are added to make these structures more effective.

Conclusion

Different types of canal falls—vertical drop, glacis, stepped, notch, and siphon—are used in hydraulic engineering to safely lower water levels in canals. Each type is chosen based on the slope, discharge, and site conditions to manage water energy, prevent erosion, and ensure steady irrigation. Canal falls are essential components of a well-functioning canal system.