GULLY CONTROL AND RECLAMATION
by ROBERT D. FLANNERY
This manual by VITA Volunteer Robert D. Flannery was first
by the Lesotho Agricultural College in Maseru, Lesotho. It
how soil erosion causes gullies, what can be done to stop
from deepening, and how to reclaim eroded soil.
The manual deals specifically with conditions in southern
However, the many photographs and clearly written text make
useful for readers in other countries as well.
soil management, and other factors have made erosion a
problem for developing countries worldwide.
Mr. Flannery was a lecturer in resource conservation at
Agricultural College when he wrote this manual. He is an
soil management with wide experience in many countries, and
lives in Berkeley, California.
The manual was originally edited, illustrated, and printed
Lesotho Distance Teaching Centre. Some changes in the text
photographs have been incorporated in this VITA edition.
Please send test results, comments, suggestions, and
further information to:
VITA Publications Service
Wilson Boulevard, Suite 500
Arlington, Virginia 22209, USA
First printing October 1980
Revised September 1981
VOLUNTEERS IN TECHNICAL ASSISTANCE
1600 WILSON BOULEVARD, SUITE 500
ARLINGTON, VIRGINIA 22209, USA
Lesotho Agricultural College
Extent of Gully Erosion in Lesotho
How a Gully is Formed
Control of Gully Erosion by Structures
How to Stop a Donga from Lengthening
How to Stop a Donga from Deepening
Control of Gully Erosion by Vegetative Growth
How to Stop a Donga from Becoming Wider
Gully Control by Diversion or Retention
Maintenance of Structural and Vegetative Measures
Causes of Gully Erosion
Plants that Help to Stabilize Structures
GULLY CONTROL AND RECLAMATION
Most of the land in Lesotho has been greatly damaged by
erosion. This book is written to help you and all
interested in fighting soil erosion and in restoring the
to productive use.
The book suggests simple but effective ways to combat this
disease that is gradually eating into the land. It tells you
how you can prevent dongas (gullies) from forming; or, if
are already formed, how you can stop them from becoming
longer, or wider.
This book will teach you how to stop a donga that is running
through your field. You can also use it in your community to
control dongas that are threatening your pasture land or
are ruining your village and destroying your roads.
Some people will use this book with school children while
others will use it with their local groups. You can also use
the book individually or with your family. The important
is that all of us do something to control gully erosion and
reclaim the land already marred by dongas.
This book was written by Robert D. Flannery, Lesotho
Agricultural College lecturer in resource conservation, with
the financial assistance of the Catholic Relief Services. It
was first published by the Lesotho Distance Teaching Centre.
EXTENT OF GULLY EROSION IN LESOTHO
Soil erosion is one of the biggest problems of this country.
Lesotho dongas are formed mainly by rain falling on bare
Gradually little streams of water are formed. These streams
wash away particles of soil and form small furrows, which
deepen and become dongas. Gully erosion has damaged most
of the land in Lesotho. It has taken away most of the soil
left us with a bare, ugly country.
Dongas interfere with farming. They encroach on our fields,
carry away fertile soil, and leave us with poor subsoil that
cannot supply our plants with nutrients.
Dongas are dangerous. They ruin our grazing land, leaving
animals thin and malnourished.
Gully erosion frustrates our efforts to improve this
It washes our roads away and breaks communication between
various parts of the country.
Dongas divide our villages and often become dens for
Gullies are a threat to the lives of our animals.
animals grazing along the edges of dongas slip and tumble
All too often the fall is fatal.
Dongas are a threat to our
lives also. Some
fall to their deaths in
Our children like to play on the slopes of dongas.
they miss a step, fall into a donga, and become crippled
At present, most of the dongas in Lesotho are becoming
deeper, and longer.
There are already 25,000 dongas in Lesotho today.
is done to bring this situation under control, we will
soon have land that is unusable.
An active gully is one that is continuing to widen, deepen,
lengthen. Most of
the gullies in Lesotho are becoming wider,
deeper, and longer.
They still carry away much of our soil
whenever it rains.
The dongas of Lesotho are very active.
HOW A GULLY IS FORMED
A donga is formed by water.
Where soil has been left loose and
bare, water can move easily along the ground.
As the water
moves on loose unvegetated soil, it carries away the topsoil
and begins to form a small channel.
A donga lengthens because
the water that flows over the head erodes backwards and
into the head's profile leaving an overhang.
This overhang will fall with time, and the cycle will begin
over again. The
water that moves in a donga flows at a greater
speed than the water
that moves in a wide
its erosive strength.
If there is nothing to
control the speed of
water in a donga, it
washes away more soil
from the bed and the
donga then deepens.
As the donga deepens,
its walls force the
water into a smaller
channel. When water
moves down a donga at increased
speed, it requires
more room. It makes
room by washing away particles
of soil from the
walls, particularly towards
the bottom of the donga.
Gradually the sides of the
donga weaken and hang over.
Ultimately, the overhanging
walls fall and the donga
widens. A donga will
lengthen, and deepen unless
some measures are taken to
control the head, bed, and
CONTROL OF GULLY EROSION BY STRUCTURES
There are measures that can be carried out to prevent the
of this country from being taken away.
You can stop a donga
from enlargening by building loose stone structures at the
of the donga and at certain points on the donga bed.
structures help to collect soil that, after some time, can
used for growing vegetation.
HOW TO STOP A DONGA FROM LENGTHENING
A donga lengthens because the head keeps collapsing and
receding. The head
of a donga becomes an overfall. As
water pours over this overfall, it erodes the bottom of the
overfall and creates an overhang.
The overhang eventually collapses,
leaving the profile of the head straight.
cycle starts over again and the donga lengthens.
this situation can be controlled by stopping the head from
receding. To do
this, you need to construct stone structures at
the donga's head to reduce the speed of water.
Here are the
steps you should follow.
1. Dig out the head
of the donga to create a gentle slope
rather than a
steep slope. This will reduce the
power of the
2. Put stones on the
area you have dug out. These stones
slow the movement
of the water. If you are dealing with a
should slant the
right to the
fill the part
have slanted with
3. At the end of the
slanted part, dig a shallow foundation in
which to put some
stones. Throw in as many stones as
to form a loose wall
of about 30cm from the level of
The loose stone structure prevents water
digging into the
soil and causing damage. It also helps
fast-flowing water from washing away soil.
however, be loose so that water may easily
pass through the
4. In the middle of
the stone structure you must leave a
the spillway. This is an outlet that
water to pass through. Unless you allow
this outlet, the force of the water will
break and wash away
HOW TO STOP A GULLY FROM DEEPENING
After building the first stone structure, you still need to
check the flow of water along the bed.
If water is allowed to
move freely along the bed after passing through the first
structure, it will continue to erode soil on the floor of
donga. You will,
therefore, need other structures that will
slow the movement of water and even trap some silt.
are called stabilization structures.
The best place for building a stabilization structure is at
spot where the gradient of the donga changes.
First, dig a
small foundation 60cm deep and 60cm wide.
Then, fill in this
foundation with stones.
Continue to pile loose stones until the
wall of stones is about 30cm high.
Leave a spillway either at each side or at the center.
On the downstream side of the wall, make a layer of flat
called an apron. Towards the end of the apron, make a
perpendicular line of stones to slow down the speed of the
CONTROL OF GULLY EROSION BY VEGETATIVE GROWTH
The main aim of gully control is to stabilize the gully by
vegetative growth. The structures mentioned will help some
plants to grow in a donga because they will trap some water
soil on which the plants can grow.
Vegetation is effective in controlling the erosive power of
water and in trapping the silt carried by the water. The
that grow naturally on the bed of a donga need to be
from animals and fires so that they can cover the gully and
Once the bed cover has been established, the donga will
to deepen; but the walls will have no cover and the donga
continue to widen. Further steps must be taken to prevent
HOW TO STOP A DONGA FROM BECOMING WIDER
To stop the donga from becoming wider, you need to grow some
vegetation on the walls. The vegetation that you grow to
the walls should have an extensive root system. You should
plant this vegetation near the bottom of the donga where it
will have moisture. Once it has taken root, it will extend
the walls and stop the donga from widening.
Walls are not the same in all dongas. Some dongas have
walls that can easily accept vegetation; others are too
straight so no vegetation
can grow on
them. To prevent a
donga with straight
walls from widening,
you should dig out
the walls to make
them slope. This
will enable creeping
grasses and legumes
to spread across the
When the grasses and
legumes seem to have
become established near
the bottom and along
the walls of a donga,
you can begin to plant
trees. Trees can only
survive where shrubs
and grasses are already
growing. Trees, shrubs,
and grasses help to
reduce the speed of the
water and trap a lot of
silt and dead plants
that are carried by the
During the establishment stage, you should not allow animals
to graze on the gullied areas. Grazing hinders the growth of
the vegetation. If you protect the area where you are controlling
gully erosion, your land should be reclaimed in a few
GULLY CONTROL BY DIVERSION OR RETENTION
You can also control donga formation by changing the course
run-off water. You can divert the water from your field,
pasture land, or road by constructing a ridged furrow on the
higher slope. The furrow made above your field or pasture
should be half-moon shaped, and it should empty the water
a protected or well-vegetated area.
In an area where gullies are beginning to form, you can make
one diversion furrow above the heads of the gullies. This
furrow can have an outlet into a location that has
structures. This would be an economical way of controlling
small dongas with one diversion furrow leading into one
At the outlet of the furrow, you can Construct a loose stone
structure. This should have an apron that will control the
of water into the stabilized area. If there are enough
you can install some stone structures along the diversion
furrow to control the velocity of the water. You should
spillway in the center of every structure for times when
is too much water running through the furrow.
You should make sure that these structures are well
for if they are destroyed by water, they can do more damage.
There are other means of controlling the speed of run-off
water. You can construct terraces on gentle slopes in your
field to check the flow of water. These terraces should be
on open soil. If the terraces hold any water, the water will
easily soak into your field.
The terraces should be left open to allow excess water to
escape. Remember that you should have some structures at the
open ends, to prevent the water from beginning a gully.
You can also make dams in gullies to retain the run-off
A dam should be made near the head of a donga so that the
steepness of a donga may be reduced. This will lessen the
of water over the head and stop the head from lengthening.
The dam should be big enough to hold the water. It should
have a spillway for emergencies. The spillway should have
structures to prevent the escapinq water from cutting into
ground to form a deeper donga. The spillway should be built
such a way that it is not used very often, i.e., only when
dam is very full.
If the spillway is not well maintained, it will be washed
by water and a donga will result. If there is no natural
below the dam, you should encourage vegetative growth.
MAINTENANCE OF STRUCTURAL AND VEGETATIVE MEASURES
When you have constructed the stone structures along the
of a donga, you must check that they are not destroyed by
water, humans, or animals.
If the stone structures begin to collapse, make immediate
repairs. Inspect the sides of the structures and repair all
cracks that might have been caused by animal burrows, dry
weather, or flood water. Repair the structures before they
apart. If you maintain the structures properly, you will
yourself costly repair jobs when unusual storms occur.
When the vegetation you have planted begins to grow, protect
from grazing animals. Even when the vegetation is
you should only allow limited grazing. The young vegetation
should be protected from fires and from being trampled on.
Spread manure around any plants that are not growing well,
you do not need to manure the whole gully.
By maintaining structures and caring for plants grown in
stabilized dongas, you will be able to restore your land.
CAUSES OF GULLY EROSION
You have learned how the dongas that eat into this land and
leave us with a desolate and ugly country can be controlled.
You should now learn how they are caused so that you can
them from occurring again.
There are many causes of gully erosion in this country. Some
causes are man-made, while others are due to animal traits.
1. Improper land use. Men sometimes become a cause of gully
erosion by using
their land improperly. They plow the
slopes; and when
rain falls, it carries away the soil that
has already been
loosened by plowing. A small gully begins
to form. If it is
not controlled in time, run-off water will
enlargen it until
a big gully is formed.
Before you plow
along the slopes, you should build a diversion
furrow to protect
your land from run-off water from the
higher slopes. The
furrow should reduce the speed of the
water that runs
down the slope. once you have made the
you should make sure that it is not
water. You can strengthen it with the stone
structures that I
have mentioned and by planting grasses or
legumes that have
extensive root systems.
will prevent your field from being cut in two
by run-off water.
It will also protect your crops from the
run-off water that
can take your plants away.
Land can carry a
certain amount of run-off water as long as
the surface of the
land is not disturbed. Sometimes farmers
plow their land up
and down. This enables the water to move
easily along the
furrows made by the plow. The water that
moves along the
furrows will carry soil as it flows down the
field. If this is
allowed to go on year after year without
any check, a gully
will be formed in the field. It is,
advisable to stop this type of plowing, as it is
a definite cause
of gully erosion.
2. Farm tracks.
These are other sources of gully erosion. If
you look at farm
tracks between fields, you will realize
that the tracks
become deeper and deeper. This is caused by
sledges and carts
that are pulled by animals. The sledges or
carts cut into the
ground, sometimes uprooting grasses that
have grown along
They break up the
track into loose soil, which is easily
carried away by
water. Given time, the farm track will
into a donga. To protect this country from
gully erosion, we
should make terraces or other structures
along farm tracks
and roads to reduce the erosive power of
Through frequent usage, footpaths become torn
and small channels
begin to form. When a footpath begins to
deepen, men stop
using it and begin a new path alongside the
old one. When it
rains, the run-off water is channeled into
the deepened path.
The channeling of water increases its
erosive power; and
with time, the path will deepen more and
more until a donga
is formed. To protect this country from
gully erosion, we
should never leave abandoned footpaths
should build terraces or other structures to
reduce the erosive
power of the run-off water.
4. Road drainage.
Road drainage may also encourage gully erosion.
ditches are dug, they should be properly
protected so that
water does not flow freely on the already
If the water moves freely, it will carry
away the soil, and
finally a donga will form because of the
Since you cannot
avoid making farm tracks, footpaths, and
it is important that you should make sure
that these are
protected so that they do not encourage donga
will need to make terraces and stone structures
vegetation to ensure that water does not
flow freely along
the tracks, footpaths, and road drainage.
5. Livestock. Animals also contribute towards gully
on the same pasture every day leaves the
ground bare. When
sheep graze where grass is short, they
remove all the
grass from the soil. This leaves the soil
unprotected. When it rains, water flows freely over
this bare ground
and at greater speed than it does where
there is grass
cover. If there is no grass growing on this
bare land, a small
gully will begin to form.
To preserve the
grass cover on the pasture land, you should
rotation. Do not let the animals graze on
the same pasture
day in and day out. Keep animals away from
one area to
encourage the grass to regrow. This is not easy
to do; but, if you
want this country to be restored to vegetative
effort is necessary.
Like men, animals
tend to form trails where they walk. Their
hoofs loosen the
soil. When it rains, the water carries the
loose soil away.
Animals will trample on the same trail
again and loosen
the soil more. After some time, you will
see a small
channel beginning to form. If you do not take
measures, a donga will result from the livestock
trails. To avoid
this, make sure you do not drive your
animals along the
same trail every day.
PLANTS THAT HELP TO STABILIZE STRUCTURES
When all your structures seem to be working well, you should
supplement them with some vegetation. It is better to
the vegetation that is already growing in the controlled
You can Supplement the natural local vegetation with other
plants that you can find within your area or buy from local
As mentioned before, grasses and legumes can be planted to
up the walls of dongas. These can be planted near the bottom
the dongas. The best plants to grow are sod-forming grass,
creepers, or leguminous plants. Grasses such as the Kikuyu,
Mohlomo (Kweekgrass), Ookoa, Thitapoho, and many other
you know can be transplanted to the controlled gully area.
can plant some grasses by using their seeds, e.g., Mohlomo,
Qokoa, and Thitapoho.
Two legumes can be used at the base of dongas. These legumes
creep along the walls of dongas. They are called Kudzu and
Crown Vetch. You can probably obtain plants or seeds from
nurseries or agriculture departments. The grasses and
make a good base for future growth of trees. Trees cannot
easily grow on a bare area.
There are several native kinds of trees that can be grown to
stabilize the controlled eroded area. The trees will grow
providing there is a grass base already prepared for them.
If there are trees already growing in the gullied area, it
better to plant trees of the same species. If the gullied
has some poplar trees already, continue growing a similar
species in the area. It would be useless to grow wattle
for they may not adapt themselves to this area as easily as
You should not forget that if you grow trees in a gullied
the banks of the dongas will need to be sloped. Trees that
proved to be useful in stabilizing gullied areas are
poplars, wattles, willows, and wild olives. You can also try
cheche, kolitsane, leloka, and lesika, if these are
A local nursery can advise you about other stabilizing
Once you have established vegetation in the gullied area,
animals should stop grazing on that land. There should be no
disturbance to the plants or structures. Check the
and structures regularly to see if there is any need for
repairs or to allow limited grazing to control competitive
weeds and shrubs. The area should also be protected from
fires. A fire will burn the seeds and roots of the plants.