FOREWORD
The FAO Watershed Management Field Manual is published within
the FAO Conservation Guide series as Conservation Guide No. 13 and will consist
of eight separate volumes:
Watershed Survey and Planning
Slope Treatment Measures and Practices
Vegetative and Soil Treatment Measures
Roadway Protection Measures
Landslide Prevention Measures
Gully Control (this volume)
Torrent Control
Water Harvesting
The objective of this Manual is to assist professionals concerned
with the planning and implementation of watershed management activities by
providing practical information supported by examples from a wide variety
of situations. However, the watershed situation in each country is unique
and it is impossible to provide step-by-step solutions which will apply in
any specific case. The user of the Manual is therefore invited to add the
local experience and information deemed necessary.
We wish to acknowledge the valuable work of Mr. M.P. Geyik on
which this volume was based; it has been edited by Mr. S. Dembner, FAO consultant,
and been prepared for publication by Mr. T. Michaelsen of the Forest and Wildlands
Conservation Branch. It is hoped that the publication will be useful to all
professionals involved in watershed management activities.
ABSTRACT
The purpose of this document is to provide practical guidance
for gully control including a description of the factors affecting gully formation
and a classification of gullies. Control measures include diversions and the
specifications for various types of check dams and gully plugs.
INTRODUCTION
Now here does the strategy "prevention is the best cure" apply better than
in gully control. Gullies usually develop because of an imbalance in run-off
conditions, and are almost always due to man's activities. Gully control is
therefore often an effort to restore a balance which need not have been destroyed
in the first place.
In most cases, gullies can be prevented through good land
husbandry - by maintaining infiltration capacity, vegetative cover, soil structure,
etc. - and by simple measures to avoid concentration of excess run-off. These
are also the measures which ensure good crop yields, growth of forest vegetation
and fodder production. The prevention of gully formation is not a burden on
the land user but a natural consequence of good land management.
Early interventions are far more economical than late ones.
A small gully or rill can easily be repaired. But if the situation is allowed
to deteriorate, the same gully may develop into something beyond economic
recovery. In most cases, gully control is aimed at preventing further damage
and loss of productive land rather than at reclaiming gullied land for agricultural
use.
This volume is based on experiences in very steep mountain areas with high
intensity rainfall. This has influenced the choice of formulas, examples, etc.
Local experience and sound judgment is needed when applying the techniques detailed
in the Manual in conditions which vary significantly from those on which it
is based. This is of particular importance in the determination of peak flows,
construction materials, choice of species and vegetation types.
