|Special Public Works Programmes - SPWP - Anti-Erosion Ditches - Training Element and Technical Guide for SPWP Workers, Booklet No. 1 (ILO - UNDP, 84 p.)|
|1. What is erosion?|
|2. How to recognise erosion|
|3. Different types of anti-erosion ditches|
|3.1 Silt catchment pits|
|3.2 Forest tiering|
|3.3 Forest terracing|
|3.4 Cropping terraces|
|4. Worksite organisation|
|4.1 Good management of the workers|
|4.2 Good selection of tools|
|4.2.1 Surveying Instruments|
|4.2.2 Tools used in the digging of ditches|
|5.1 Site selection|
|5.2 Siting of the ditches|
|5.3 Plotting the dimensions of the ditch|
|5.4 Preparing the surface soil of the ditch site|
|5.5 Excavating the ditch|
|5.6 Checking the dimensions of the ditch|
|5.7 Constructing the retaining banks|
|5.8 Checking that the retaining banks are horizontal|
|5.9 Improving the waterways|
|5.10 Protecting the slopes|
|6. Maintenance of the retaining banks|
(a) The PICKAXE
This tool consists of a long wooden handle and a metal head. The metal head is double-ended: one end is pointed and the other is in the form of a wide cutting edge.
The pointed end is used to pierce through the hard surface of the soil and to break up stony ground.
The cutting edge is useful for slicing through roots and for shifting clods of earth.
(b) The DABA (traditional African hoe)
The daba can be used in place of a pick on soft ground.
It is also used to scrape the surface of the ground clear of vegetation.
DABA (traditional African hoe)
(c) The SHOVEL and SPADE
There are several variations of the basic shovel and spade. The most commonly used for earthworks are the round-mouthed shovel and square-mouthed spade.
This type of shovel is ideal for digging but is ineffective when it comes to scraping flat surfaces. On soft or sandy ground, a square-mouthed spade is equally useful. This latter type has a wide straight cutting edge. A tread is fitted to the top of the metal head to enable the worker to force the spade into the ground with his foot.
(d) The CROWBAR
This tool is essentially a solid metal bar which is used to penetrate and break up rocky ground.
An improvised crowbar can be forged from a length of 16 mm reinforced iron. One end is pointed to break through rock and the other flattened so that the bar can be struck with a sledgehammer.
We use the crowbar when the going becomes too difficult for the shovel or spade.
To break through rock, the following procedure is used:
- Select the weaker areas of the rock where cracks are to be found.
- Place the pointed end of the crowbar inside one of the cracks
- Force the crowbar into the crack by hitting its other end with a sledgehammer.
- Holding the-top of the crowbar, move it backwards, forwards and from side to side to separate the pieces of rock.
- Remove the loosened pieces of rock.
USING A CROWBAR - 1
USING A CROWBAR - 2
USING A CROWBAR - 3
(e) The SPLITTING WEDGE
This is simply a forged piece of metal which is used to break up already cracked rock. It has a pointed side which is wedged into a crack and a flat side which is struck with a sledgehammer.
- Wedge the pointed side into a crack in the rock.
- Strike the flattened side with a sledgehammer in order to widen the crack.
- Clear the rocks away by hand or with a pickaxe.
(f) The EARTH RAMMER
This tool is made up of a circular plate of metal or wood attached to a 1.30 m long wooden handle.
Its purpose is to pack down the earth: in the context of ditch-digging, it is used more particularly to pack down the retaining banks.
(g) The PLOUGH
This implement is used to break up and turn over the uppermost layer of soil. A farmer ploughs a field as the initial step towards cultivating the land. The plough can also be employed in the construction of anti-erosion ditches. In the latter context, its role is to break up the soil and render it easier to dig. Ploughs are drawn either by animals (oxen, buffalo, horses, camels) or by tractor. They may vary in form but the basic implement must include:
- a ploughshare which acts as a blade, cutting the turf and turning it over;
- two handles with which the operator can steer the implement;
- some type of harness or hitch.
SINGLE FURROW PLOUGH
TRADITIONAL ASIAN PLOUGH