Correct Answer - Option 1 : Canal falls
Explanation:
Canal Falls
Whenever the available natural ground slope is steep than the designed bed slope of the channel, the difference is adjusted by constructing vertical ‘falls’ or ‘drops’ in the canal bed at suitable intervals, but such a drop in a natural canal bed will not be stable and, therefore, in order to retain this drop, a masonry structure is constructed. Such a structure is called a Canal Fall or a Canal drop.
Depending on the ground level conditions and shape of the fall the various types of fall are:
1. Ogee Fall: This type of fall has gradual convex and concave surfaces i.e. in the ogee form.
2. Stepped Fall: It consists of a series of vertical drops in the form of steps. This is suitable in places where sloping ground is very long and requires a long glacis to connect the higher bed level u/s with lower bed level d/s.
3. Vertical Fall (Sarda Fall): It is suitable when canal u/s bed is on the level of upstream curtain wall, canal u/s bed level is below the crest of curtain wall
4. Rapid Fall: When the natural ground level is even and rapid, this rapid fall is suitable. It consists of long sloping glacis.
5. Notch Fall: In this type a body or foundation wall across the channel consisting of several trapezoidal or rectangular notches between side pier and intermediate pier is constructed.
6. Flumed Fall: In the flumed type length of the body wall of a fall is less than the normal canal width. The section is restricted at the site of the fall. The narrowing of the section is done gradually.
