Describe the various type of fall with neat sketch also discuss the suitable of each type

 Why Canal fall necessary in Canal system ?State the various type of fall with long sketches also state the suitability of each type.

Answer
Whenever the available natural ground sloope to steeper than the designed bed slope of the channel the difference is adjusted by constructing vertical fall or drops in the canal bed at sweetable intervals search type in natural canal bed will not be stable and therefore in order to retain this drop a masonry structure is constructed such a pucca structure is called Canal fall or a Canal drop.

Types of Canal Fall

Ogee Fall

• The ogee fall was constructed by Sir Proby Cautley on

the Ganga Canal. This type of fall has gradual convex

and concave surfaces i.e. in the ogee form. The gradual

convex and concave surface is provided with an aim

to provide smooth transition and to reduce

disturbance and impact. A hydraulic jump is formed

which dissipates a part of kinetic energy. Upstream

and downstream of the fall is provided by Stone

Pitching.

                                                                             Ogee Fall

Stepped Fall

• It consists of a series of vertical drops in the form of
steps. This steps is suitable in places where sloping
ground is very long and require a long glacis to
connect the higher bed level u/s with lower bed level
d/s. it is practically a modification of rapid fall. The
sloping glacis is divided into a number drops to bring
down the canal bed step by step to protect the canal
bed and sides from damage by erosion. Brick walls are
provided at each drop. The bed of the canal within the
fall is protected by rubble masonry with surface
finishing by rich cement mortar.

Stepped Fall

Vertical Fall (Sarda Fall)

• In the simple type, canal u/s bed is on the level of
upstream curtain wall, canal u/s bed level is
below the crest of curtain wall. In both the cases,
a cistern is formed to act as water cushion. Floor
is made of concrete u/s and d/s side stone
pitching with cement grouting is provided. This
type of fall is used in Sarda Canal UP and
therefore, it is also called Sarda Fall.

Vertical Fall (Sarda Fall)

Rapid Fall

• When the natural ground level is even and
rapid, this rapid fall is suitable. It consists of
long sloping glacis. Curtain walls are
provided on both u/s and d/s sides. Rubble
masonry with cement grouting is provided
from u/s curtain wall to d/s curtain wall.
Masonry surface is finished with a rich
cement mortar.

Rapid Fall

Straight Glacis Fall

• It consists of a straight glacis provided with a
crest wall. For dissipation of energy of flowing
water, a water cushion is provided. Curtain
walls are provided at toe and heel. Stone
pitching is required at upstream and
downstream of the fall.

Straight Glacis Fall

Trapezoidal Notch Fall

• It was designed by Reid in 1894. In this type a
body or foundation wall across the channel
consisting of several trapezoidal notches between
side pier and intermediate pier is constructed.
The sill of the notches are kept at upstream bed
level of the canal. The body wall is made of
concrete. An impervious floor is provided to
resist the scouring effect of falling water.
Upstream and downstream side of the fall is
protected by stone pitching finished with cement
grouting

Trapezoidal Notch Fall

Well or Cylinder Notch Fall

• In this type, water of canal from higher level
is thrown in a well or a cylinder from where
it escapes from bottom. Energy is dissipated in
the well in turbulence. They are suitable for
low discharges and are economical also.

Montague Type Fall

• In the straight glacis type profile, energy
dissipation is not complete. Therefore,
montague developed this type of profile
where energy dissipation takes place. His
profile is parabolic and is given by the
following equation,

Inglis or Baffle Fall

• Here glacis is straight and sloping, but baffle
wall provided on the downstream floor
dissipate the energy. Main body of glacis is
made of concrete. Curtain walls both at toe
and heel are provided. Stone pitching are
essential both at u/s and d/s ends