Gully Erosion Control Measures Temporary check dam Brushwood dams One row or single post brush wood dam Double row post brush wood dams. Semi permanent dams Loose rock dam Netting dam Log check dam Permanent check dam Drop Spillway Drop inlet spillway Chute spillway

1. GULLY EROSION CONTROL
MEASURES
Lecture-9
Dr. Ajay Singh Lodhi
Assistant Professor
College of Agriculture, Balaghat (M.P.)
Jawahar Lal Krishi Vishwa Vidyalaya, Jabalpur (M.P.)

2. Gully Control
 Gullies are formed by excessive surface runoff,
flowing with high velocity and force, that are
sufficient to detach soil particles from the flow
path.
For controlling gully erosion, the following
considerations are very important:
 Improving the catchment area of the gully.
 Stabilization of gully head.
 Safe conduct of water through the gully,
provided that it is not a part of natural drainage
system of the area.
 Adoption of gully control structure to stabilize
them.
Components of a Gully

3. Design Requirements of Gully Control Structure
 The gully control structures primarily designed for safe disposal of excess
runoff generated from the watershed.
 While designing gully control structures three major points are considered:
 Structure must have sufficient provision for safe discharge,
 The structure should have sufficient strength to withstand the pressure
exerted by flowing water and
 The structure should be protected from erosion due to the flow passing over it.
These points refer to hydrologic design, structural design and hydraulic design
of structures. However, the design vigor depends on the type of gully control
structures such as permanent structures require more vigorous design than
temporary structures.

4. Functions or Purpose
 The primary function of gully control structures is to provide safe passage to
the flow through intervening into the prevailing slope of natural channel.
The other purpose or function of gully control structures are listed below.
 To reduce runoff erosive forces by stacking off the gradient of a gully and by
controlling the course of flow to minimize ill effect on the banks.
 To store water in the upstream as channel storage for irrigation.
 To block sediment to keep it from damaging the downstream environment.
 To maintain the stability of soil when vegetative cover is being established.

5. Causes of Failures
 The structure failure caused mainly due to faulty hydrologic, hydraulic or structural
design either alone or combination of these. However, there are cases when structures
failed because of
 Insufficient capacity of structure
 Insufficient provision for dissipation of kinetic energy within the confine of structure
 Unprotected banks near to upstream of structures,
 Improper foundation causing uplift pressure to prevail over the body of the structure.
Types of Structures
 Gully control structures can be grouped into two categories, namely, temporary gully
control structures and permanent gully control structures.
 Temporary gully control structures are made up of locally available material and are
designed for 3-8 years. Most of the check dams come under the category of
temporary gully control structures.
 On the other hand, permanent gully control structures are designed for 25 to 50 years
period.

6. Classification of Check Dam: The check dams are classified as:
 Temporary check dam
 Brushwood dams
 One row or single post brush wood dam
 Double row post brush wood dams.
 Semi permanent dams
 Loose rock dam
 Netting dam
 Log check dam
 Permanent check dam
 Drop Spillway
 Drop inlet spillway
 Chute spillway
Temporary Structures
 All temporary structures should be practiced in G-1 type gullies.
 The purpose of this kind of dam is to temporarily maintain the stability of a gully and to make possible
the establishment of vegetative cover.
 These are not durable and need frequent maintenance, though these are inexpensive and easy to
build.
 These structures are constructed using the locally available material.
 The life of temporary structure is limited to 3-8 years.

7. Design Criteria of Temporary Structures
 The overall height of a temporary check should not ordinarily be more than 75
cm. An effective height of about 30 cm is usually considered sufficient. Minimum
15 cm freeboard is necessary.
 Life of the check dams under ordinary conditions should be 3-8 years and hence
should be design for rainfall of 10 years return period.
 Since the purpose of check dams in gully control is to eliminate grade in the
channel, check dams theoretically should be spaced in such a way that the crest
elevation of one will be same as the bottom elevation of the adjacent dam up-
stream. Hence horizontal interval depends on the channel slope and height of
check dam. Check dams of lesser height in higher slope will require more
frequent check dams down the stream.
 Suitable apron should be provided to avoid the souring due to the flow passing
over these check dams. For this purpose, rip-rap is provided in the length of 1 to
1.5 meter downstream of the check dams. The gap between the rip-rap can be
seeded with grass.

8. Brushwood Check Dam
 Brushwood check-dams are temporary structures and should not be used to
treat ongoing problems such as concentrated run-off from roads or cultivated
fields. They can be employed in connection with land use changes such as
reforestation or improved range management until vegetative and slope
treatment measures become effective.
 Brushwood check-dams made up of posts and brushes are placed across the
gully.
 The main objective of brushwood check-dams is to hold fine materials carried by
flowing water in the gully.
 Small gully heads, no deeper than one meter, can also be stabilized by
brushwood check dams.
 The main requirement of temporary gully control structures is that, they must be
quick and easy to construct, should be made by using cheap and readily
available material in nearby areas.

10. Single Row Brushwood Check Dam
 These check-dams can be used where the rate of runoff is less than 0.5 m3/sec.
 The structure is temporary and its durability will depend on the quality of posts
used. If possible live posts of willow, popular and other trees should be used (8-
10 cm dia). Flexible branches are cut and woven around the posts.

11.  This dam is constructed across the channel or gully with the brush wood
materials, laid along the flow of water, keeping the butt ends towards u/s face of
the gully.
 The brushwood is kept in position by tying to the posts.
 Before the dam construction is begun, the sides of the gully or channel should be
sloped to 1:1 and the gully bed should also be excavated for 15 cm depth along
the entire gully width over which brushwood have to be laid. In addition, 15 cm
excavation is also done into the bank to give necessary notch capacity.
 After excavation, the wooden posts of about 10 cm in diameter are driven in a
line across the gully at an interval of 90 cm up to a depth of 75 cm in gully bed.
 The top of wooden posts should be kept at such a height so as to form a notch of
required size.
 The brushwood is tied from the front line and the other lines are tied using
galvanized wire for keeping them in position. The lowest layer of the brushwood
must be the longest.

12.  This type of brushwood check-dam is suited
where the rate of runoff is less than 1m3/sec.
 The construction of the dam starts with an
excavation in the floor and into the sides of the
gully to a depth of 0.3-0.5 m.
 Two rows of posts, 5-10cm in diameter and 1-
2m in length are placed into the holes, across
the floor of the gully to a depth of 0.5-0.6m.
The spacing between the posts is 0.5 m.
 Brushwood or branches are packed between
the posts.
 The height of the posts in the center should
not exceed the height of the spillway otherwise
the flow will be blocked and water may be
forced to move to the gully sides.
Double Row Brushwood Check Dam

13.  This type of check dam is simple in
construction and very effective for gully
control.
 These dams are preferred in those areas,
where plenty of loose rocks are available
nearby the gully.
 The loose rock-fill dams are constructed with
the help of stones.
 The stones are kept across gully width by wire
netting made of fairly stout gauge of
galvanized iron wire.
 The wire netting of about 2 meter or more in
width is laid across the gully bed and over it
the loose rocks are packed approximately up
to half of the width of netting. The other half of
netting is wrapped over the stones and laced
to the other edge.
Loose Rock-fill Dam

14. Design and construction specifications of loose stone check-dam
 The foundation of the dam is dug so that the length of the foundation will be
more than the length of the spillway.
 The width of the foundation depends upon the reservoir level height.
 The dam should be properly keyed across its base and up the abutments to the
crest elevation.
 An adequate spillway should be provided for safe disposal of water.
 An apron of non erodible material should be provided at the base, to dissipate
the energy of water falling through the spillway.
 Proper spacing between the successive dams should be ensured
 The height of the dam should be properly planned
 Stones should be placed such that they interlock easily and form a denser
structure. If small stones are to be used they should be placed in the center and
the outer surface covered with large stones to strengthen the dams.
 Loose stone check-dams can be strengthened by covering the upstream wall
and the crest with bamboo/reed-mat.

15.  When large size timbers are readily
available in the nearby area of gully, the
log check dams are used for checking the
gully.
 In this dam, the logs are used as
brushwood but they make the structures
substantially stronger.
 In the log check dam, two rows of vertical
wooden posts are formed by inserting the
wooden posts in line with the gully bed
and extending up to the sides above the
flood level and then logs are packed
between the two rows.
 The vertical posts should be at least 10
cm in diameter and 2 m long.
Log Check-dam

16.  The spacing should be kept about one meter between each row, with the two
rows of posts half meter apart.
 In wide and shallow gullies, it is better to keep all vertical post to a height of 60
cm above the ground surface so that the top of the dam can follow the section of
stream bed. If the gully has steep sides, it should have a rectangular notch in
the centre but the notch must be large enough to pass whole of runoff.
 The vertical posts on either sides of notch are responsible for dissipating the
kinetic energy of flowing water. Therefore logs should not be swept down by the
flow, for which stout posts must be driven to a greater depth than the others.
 When the logs are fully packed between the rows of posts, the bottom layer to
be sunk below the dam may be checked.

17.  In this dam wire netting is used to form a
small check dam.
 The netting dams are usually located near
the top end of the gullies.
 This dam consists of wooden posts which are
driven into the gully bed to support a strip of
wire netting and thus, forming a low wall
across the gully.
 The height of dam is kept about 60 cm. The
lower edge of the netting is buried into the
gully bed.
 The brush or straw is also piled loosely
towards upstream side of the netting wall to
form a barrier, which is porous in nature. But
it slows down the flow velocity and results in
deposition of sediment on the upstream side.
Netting Dam

18.  Sandbag check-dams are made from used
jute or polyethylene bags (50 kg) filled with
soil/sand.
 The bags are piled up to a maximum of 3 – 4
layers to form a small check-dam.
 This cheap technique is particularly useful in
areas with insufficient supply of stones for
building ordinary check-dams.
 By erecting sandbag dams large rills or small
gullies (finger gullies) can be controlled, while
they are not suitable for the treatment of
large gullies.
GUNNY BAG/ SAND BAG CHECK DAM

19.  It is basically a rectangular wire mesh box, filled
with stones.
 The size of stones filled is always greater than
the mesh openings.
 These structures are flexible, permeable and
economical, are constructed in those places,
where stones are abundant.
 The boxes are made of galvanized wires to
ensure longer service life, as these wires are
less succeptible to get affected by rust
formation.
 The gabion structures are meant for controlling
the soil erosion under different conditions.
These are also used for torrent control works,
controlling the land slip, land slides, gully control
and river bank protection works.
GABBION STRUCTURE

20. Spillways:
 A spillway is defined as a structure, constructed either in dam section or in gully
for effective and safe disposal of water from upstream to downstream end.
 As per term meaning, the spillway is a path to cross the flow from one end to
other end.
 The basic components of spillway, used as permanent gully control structures
(hydraulic structure) are inlet, conduit and the outlet.
 Water enters the structure through the inlet and is conveyed through the conduit.
The water leaves the structure through the outlet.
 The outlet is mainly designed for dissipating the kinetic energy of flowing water
so that water leaving the structure can not cause erosion towards downstream
side of the structure.
PERMANENT GULLY CONTROL STRUCTURES

21.  This structure consists of a pipe passing through an earth fill dam, linked with a
suitable inlet and outlet.
 The inlet is installed having some drop which causes to flow of water from inlet
to conduit.
 The outlet usually consists of a propped pipe or a chute. The size of outlet
should be sufficient to provide an adequate flow to the downstream channel.
DROP INLET SPILLWAY

22.  This structure is versatile in use. It is a very efficient structure for controlling
relatively high gully heads, usually more than 3m.
 It also serves as gully control structure, where large drops of gully profile are
needed to eliminate.
 These are also used to raise the grade of deep gullies. Also, for flood control, the
drop inlet spillways are ideally used, as they are constructed with an earth fill
dam which forms enough storage capacity above the structure to hold the runoff.
Thus drop inlet spillways have the dual purpose of gully and flood control.
However, the various uses of drop-inlet spillways are also given below.

23. Uses of Drop inlet Spillway: The various functional uses of this structure are
given as under:
 It is used as a principal spillway in case of farm ponds or reservoirs for letting out
the water.
 For stabilization of gully grade.
 It is used at lower end of water disposal system.
 This spillway can be used in combination of check dams for the safe disposal of
water, stored in the reservoir.
 In forest roads, it can be used as culvert.
 In debris basins, it is used as principal spillway.
 For controlling the flood, it is equally used.
 Used as a channel water inlet in drainage or irrigation structures.

24. Advantages- It has following main advantages
 This spillway requires comparatively less construction material than the drop
spillway for the same heads.
 The capacity of this spillway can be reduced, particularly where an appreciable
amount of temporary storage is available.
 Construction cost is less.
 For stabilisation of gully grade and prevention of flood, it is one of the most
efficient structure.
Limitations
 Small size or small capacity drop-inlet spillways are more susceptible to get
chocked by debris present in the flow water.
 Where greater earthwork is required for construction, it is not recommended for
use.

25.  Chute spillway is an open channel like structure, which is constructed on steep
slope of the gully face with a suitable inlet and outlet.
 Such spillways are used at the locations where head drop is fairly large ranging
from 5 to 6 m.
 They are normally constructed to handle a full flow at the gully head. Since they
are used at larger drop i.e. over the gully head, so their main function is to
control the gully head from its enlargement by waterfall erosion.
 Chute spillway handles the flow having super critical velocity.
 Chute spillways usually require less concrete work than the drop- inlet structure
for the same capacity and drop. But they are more danger of undermining by
rodents and threatening of foundation due to seepage in poorly drained
locations.
 The chute structures do not provide any storage of water towards upstream
side.
CHUTE SPILLWAY

26. The chute spillways are suitable for
following conditions:
 For high overfalls, where a full flow
structure is required.
 Where site conditions are not suitable for
constructing check dams.
 This spillway can also be constructed in
combination of check dams and other
detention-type structures.
Its main uses are as follows:
 For control of gully head.
 For conveying the runoff from u/s areas into the gully, very smoothly without erosion.
 It may be used as a structure for flood prevention, water conservation and collection
of sediments.
 For controlling the gradient of natural or artificial channels.

27. Limitations: The various limitations of chute spillway are as under :
 There is considerable danger of undermining due to rodents. For which,
additional precautions are required to count.
 In poorly drained areas, there is problem of seepage. Such areas are not
suitable for chute spillways, as seepage tends to weaken the foundation. In
such areas if construction of chute spillway is very essential and no other
substitutes are available, then provisions to control the seepage problem are
essentially made.
 For safety point of view, the construction site should be compacted very well or
when earth filling is done that should also be compacted thoroughly. It is an
additional work, which takes time and money both.

28.  It is one of the most suitable and common permanent gully control structure which is
mainly used at the gully bed to create a control point. Several such drop structures are
constructed across the gully width through out the length at fixed intervals.
 The series of such structures, develop a continuous break to flow of water, causing
deposition of sediments and thus to filling the gully section. Sometimes, the drop
structures are also used at the gully head to pass the flow safely and controlling the
gully head.
 The drop structures are used upto the drop of about 3 m.
There are following three major purposes of the use of drop structure.
 To provide a transition between a broad or flat waterway and ditch or gully section.
 To raise the flow line i.e. to form sufficient soil depth for vegetative growth where
bottom of the gully is on risk.
 To raise the flow line of the waterway so as to provide drainage in the case of wet
waterways.
STRAIGHT DROP SPILLWAY

29. The various functional uses of this spillway are given as under:
 It is used for grade stabilization in lower reaches of waterways and outlets.
 Used for erosion control, to protect the roads, building etc.
 Straight drop spillway can be used as an outlet in tile drainage system and for
releasing the irrigation water into the field in irrigation system.
 In reservoir it is used for letting out the water, provided that total drop of spillway
is low i.e. not more than 3 m.
 It is also used for controlling the tail water at the outlet section of the conduit or
spillway.
 For controlling irrigation, the drop spillways are also used in the water
distribution system.

30. Advantages: These are as follows-
 In this structure, the danger of undermining
by rodents is not possible.
 Straight drop spillways are less succeptible
to get structural damaged, than the other
structures.
 As in other spillways (especially in drop-inlet
spillway) the conduit is likely to be clogged
by debris, but in this spillway there is no
such problem.
 Its construction is very easy; a village
mansion can easily construct it.

31. Limitations
 In the areas, where discharge is less than 3 m³/s and total head or drop exceeds
3 m, the construction of straight drop spillway prooves to be a costly affair,
should not be preferred.
 It requires a stable gully grade below the structure.
 The construction of this structure is not technically justified, particularly where
temporary storage is required to obtain a reduction in discharge.

32. Thank You