1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

Yes

1.4 Declaration on sustainability of the described Technology

Is the Technology described here problematic with regard to land degradation, so that it cannot be declared a sustainable land management technology?

No

2.1 Short description of the Technology

Definition of the Technology:

Permeable rock dikes are erosion control structures to slow down runoff

2.2 Detailed description of the Technology

Description:

Permeable rock dikes are erosion control structures built along the natural contour of the land and designed to slow down runoff. They are built between 30 and 50 cm high and twice or three times as wide as they are high. They are made with different-sized stones and rocks, and the crest of the dike is horizontal. There are two main types of permeable rock dike: those without a filter layer, which are suitable for flat land with no gully erosion and those with a filter layer suited to land with heavy runoff.

Because of the way it is constructed, it dissipates the erosive force of the water. Sediment builds up behind it, resulting in the formation of terraces. It also increases the infiltration of surface water into the soil. The retention of water and fertile sediment by the dikes facilitates the development of natural vegetation along the structure. Grass and bush seeds are trapped by the dikes, favouring the spontaneous growth of natural vegetation, which contributes to restoring biodiversity and provides a habitat for wildlife. Good tree and grass cover developed along the dikes contributes to lowering soil temperature and reducing wind erosion along the entire length of the structure.
The reduction in runoff downstream of the dikes contributes to reducing alluvial deposits in the valleys further downstream. Watershed development with permeable rock dikes reduces siltation and gully erosion.
Permeable rock dikes are designed for use on cropland, but can also be used on forest/rangeland. They are recommended for ecological units with gravely and sandy-clayey soils and pediments. They can also be used to fill in small rills.
Studies conducted in the PATECORE area show that plots with permeable rock dikes averaged sorghum yields of 795 kg compared with 576 kg on control plots, which means that yields were 38% higher on improved plots. The production of straw for livestock increases in the same proportion as grain output.

With some upkeep, permeable rock dikes last at least 20 years. Before the rainy season starts, any stones dislodged by animals must be replaced. During the rainy season, the water can wear gaps in the dikes, which must be repaired immediately. The stability of the dikes can be reinforced by active revegetation (by sowing grass or planting trees). Without direct sowing, natural vegetation develops along the dikes after several years.

From the point of view of climate change adaptation, permeable rock dikes mitigate the effects of variations in rainfall. They are appropriate in wet period with heavy rain and violent downpours: permeable rock dikes constructed on the upper edge of the plot as a protective measure and a means of improving infiltration, protect land at risk from erosion. They are also appropriate during dry periods as they stop or slow down the flow of water. Permeable rock dikes improve infiltration and therefore increase and prolong the availability of water for crops. The permeable rock dike differs from the contour stone bund in that it is bigger in size, is constructed with various layers of stones and is designed to control stronger water flow. For this reason, such dikes are often constructed up-stream of stone bunds to dissipate the force of the water flowing from the plateaux and slopes.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

2.6 Date of implementation

If precise year is not known, indicate approximate date:

• 10-50 years ago

2.7 Introduction of the Technology

Specify how the Technology was introduced:

• through projects/ external interventions

Comments (type of project, etc.):

developed, implemented and disseminated as part of projects and programmes undertaken from the 1980s onwards to combat desertification and improve natural resource management. Implemented by GIZ (German Federal Enterprise for International Cooperation), and PATECORE (project for land development and resource conservation in Plateau Central)

3.1 Main purpose(s) of the Technology

• reduce, prevent, restore land degradation

3.2 Current land use type(s) where the Technology is applied

Cropland

• Annual cropping

Number of growing seasons per year:

• 1

Specify:

Longest growing period in days: 120, Longest growing period from month to month: August to October

Grazing land

Extensive grazing:

• Semi-nomadic pastoralism

Comments:

Major land use problems (compiler’s opinion): surface runoff, soil erosion by water and wind, fertility decline
Constraints of common grazing land
Constraints of forested government-owned land or commons

3.5 SLM group to which the Technology belongs

• cross-slope measure

3.6 SLM measures comprising the Technology

structural measures

• S2: Bunds, banks

3.7 Main types of land degradation addressed by the Technology

soil erosion by water

• Wt: loss of topsoil/ surface erosion
• Wg: gully erosion/ gullying
• Wo: offsite degradation effects

soil erosion by wind

• Et: loss of topsoil

chemical soil deterioration

• Cn: fertility decline and reduced organic matter content (not caused by erosion)

biological degradation

• Bc: reduction of vegetation cover

water degradation

• Ha: aridification

Comments:

Main causes of degradation: crop management (annual, perennial, tree/shrub) (Unadapted landuse methods, reduced or abandoned fallow periods), floods, droughts, population pressure (rapidly growing population increasing pressure on land), land tenure (insecure access to land)

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:

• reduce land degradation
• restore/ rehabilitate severely degraded land

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

Permeable rock dikes are built between 30 and 50 cm high and twice or three times as wide as they are high. They are made with different-sized stones and rocks, and the crest of the dike is horizontal. There are two main types of permeable rock dike: those without a filter layer, which are suitable for flat land with no gully erosion and those with a filter layer suited to land with heavy runoff.

Technical knowledge required for field staff / advisors: moderate
Technical knowledge required for land users: low
Main technical functions: control of dispersed runoff: retain / trap, control of dispersed runoff: impede / retard, control of concentrated runoff: retain / trap, control of concentrated runoff: impede / retard, control of concentrated runoff: drain / divert, reduction of slope angle, improvement of ground cover, increase in nutrient availability (supply, recycling,…), increase of infiltration, increase / maintain water stored in soil, water harvesting / increase water supply, sediment retention / trapping, sediment harvesting
Secondary technical functions: stabilisation of soil (eg by tree roots against land slides), increase in organic matter, increase of groundwater level / recharge of groundwater, reduction in wind speed, promotion of vegetation species and varieties (quality, eg palatable fodder)

Bund/ bank: graded
Height of bunds/banks/others (m): 0.3-0.5
Width of bunds/banks/others (m): 1.5

Author:

PATECORE, GIZ

4.3 Establishment activities

4.5 Maintenance/ recurrent activities

4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)

Comments:

Machinery/ tools: pickaxes, shovels, wheelbarrows, water-tube level, etc.

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

The exact cost of constructing permeable rock dikes per hectare depends on the distance of the site from the quarry, the inclination of the terrain, which determines the spacing between the dikes, and the actual amount of stones transported in each lorryload or cartload. Supply of quarry rock/stones: 48 m3 for 200 m of dike.
Labour: 60 man-days per ha
• levelling and marking out the contour line: 1 man-day
• collecting stones and loading them onto carts:
20 man-days
• transporting the stones by cart: 20 man-days
• building the dikes: 19 man-days
• applying manure.
Transportation by cart:
• 20 cartloads of stones
• 20 cartloads of manure (if used).
Transportation by lorry:
• 11 lorryloads (skip loader – 4.5 m3 per load).
Other costs:
• equipment (pickaxes, shovels, wheelbarrows, water-tube level, etc.).

5.1 Climate

5.2 Topography

5.3 Soils

5.4 Water availability and quality

5.5 Biodiversity

5.6 Characteristics of land users applying the Technology

Indicate other relevant characteristics of the land users:

Population density: 10-50 persons/km2
Annual population growth: 3% - 4% (mostly poor households below poverty line).
Off-farm income specification: men migrate temporarily or permanently to cities for off-farm income

5.7 Average area of land used by land users applying the Technology

5.8 Land ownership, land use rights, and water use rights

Land ownership:

• state

Land use rights:

• communal (organized)

Water use rights:

• communal (organized)

Comments:

traditional land use rights on fields, communal land on pasture and forest land

5.9 Access to services and infrastructure

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

Income and costs

Socio-cultural impacts

Ecological impacts

Water cycle/ runoff

Soil

Biodiversity: vegetation, animals

Climate and disaster risk reduction

6.2 Off-site impacts the Technology has shown

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change

Climate-related extremes (disasters)

Meteorological disasters

Climatological disasters

Hydrological disasters

Other climate-related consequences

Other climate-related consequences

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?

6.5 Adoption of the Technology

Comments:

There is a little trend towards spontaneous adoption of the Technology
The technique’s potential for replication depends on the type of terrain and the availability of a supply of stones within a reasonable distance. The technique is very effective as a flood control measure and is relatively easy to learn. Farmers are able to implement the technique themselves after two days’ training. This technique can only be implemented with highly motivated groups and villages, with strong working and mobilisation capacities.

6.7 Strengths/ advantages/ opportunities of the Technology

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

Good Practices in Soil and Water Conservation. A contribution to adaptation and farmers´ resilience towards climate change in the Sahel. Published by GIZ in 2012.

Available from where? Costs?

http://agriwaterpedia.info/wiki/Main_Page