Technologies

Filtering dyke [Burkina Faso]

Creation: 03/16/2023 11:36 a.m.
Update: 05/20/2024 3:17 p.m.
Compiler: Moussa ABOU
Editors: Siagbé Golli, Brice Sosthène BAYALA, Tabitha Nekesa, Ahmadou Gaye
Reviewers: Sally Bunning, Rima Mekdaschi Studer, William Critchley

Kabakourou Walandéni (Dioula)

technologies_6691 - Burkina Faso

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Completeness: 88%

1. General information

2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

A filtering dyke is a water and soil conservation technology built into a temporary stream, valley bottom or a drainage channel. It is built using stones of varying sizes.

2.2 Detailed description of the Technology

Description:

A filtering dyke is a stone bund built across a gully in eroded soil, in valleys or drainage channels/small seasonal/temporary streams, in Sahelian and South Sudanese climates with average annual rainfall ranging from 400 to 1100 mm.
The structure is built on a contour line in order to reduce runoff velocity and erosive energy. It comprises stones and rubble in a bund measuring 50 cm in height and 150 cm in width. The dyke contributes to sedimentation upstream, thereby reducing the slope and enhancing surface water infiltration into the soil. Tillage should be avoided to create a stable pathway for runoff water, which may also be vegetated with perennial grasses for gully/watercourse stabilization.
Typically, the spacing between dikes along a watercourse or gully is 20 m. The key steps involved in constructing a filtering dyke are as follows:
* Siting:
•Determine a contour line using a water tube level;
•Mark the contour using tools like a daba, a pick, a pickaxe, IR12 cattle-drawn tine, tractor, stake, etc. ;
•Smoothen the contour line, if necessary, to reduce irregularities;
•Tie a string across the gully at the location chosen during technical identification of the site;
•Place stakes on both banks, notching them at a height of 50 cm to indicate the bund's design height.

* Clearing the foundation trench:
•Clean the designated area on the ground;
•Open a 20 cm-deep anchoring trench along the marked-out rope, disposing of the soil downstream of the bund.

* Design of structure with respect to water flow

* Laying the rubble and stones:
•Fill the excavated soil with gravel to around 20 cm depth.
•Place large stones upstream, followed by medium-sized stones in subsequent rows, moving downstream.
•Fill any gaps;
•Lay a second layer of loose stones, with an upstream slope of 1/1 (vertical) and a downstream slope of 1/2, until the desired height of 50 cm is reached;
•Build the edge of the structure with large stones for stabilization, deposited in an open trench downstream.

In an agricultural area, this technology must be accompanied by contour ploughing (perpendicular to the slope), to reduce the risk of erosion and accelerated runoff.
The benefits of filtering bunds include runoff control, erosion reduction, enhanced infiltration, soil moisture conservation, groundwater recharge contribution, and increased water storage in the soil. They combat land degradation by enhancing upstream water infiltration and sedimentation of sand, clay, and organic debris. Water conservation and the retention of fertile sediments by the bunds facilitate the development of natural vegetation alongside the structures, thereby restoring biodiversity and protecting structures. Although implementation may pose challenges for landowners, they recognize its effectiveness in combating water erosion and conserving soil and water resources.

2.3 Photos of the Technology

Media Gallery

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

Country:

Burkina Faso

Region/ State/ Province:

Hauts-Bassins, Houet Province

Further specification of location:

Sébédougou (Commune of Koumbia)

Specify the spread of the Technology:

applied at specific points/ concentrated on a small area

Is/are the technology site(s) located in a permanently protected area?

Comments:

The technology is implemented at the scale of a micro-catchment .

2.6 Date of implementation

Indicate year of implementation:

2020

2.7 Introduction of the Technology

Specify how the Technology was introduced:

through projects/ external interventions

Comments (type of project, etc.):

The specific technology was introduced by ProSoil, but similar structures have been built in Burkina Faso since the 1980s.

3. Classification of the SLM Technology

3.1 Main purpose(s) of the Technology

improve production
reduce, prevent, restore land degradation
protect a watershed/ downstream areas – in combination with other Technologies

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

Land use mixed within the same land unit:

Yes

Specify mixed land use (crops/ grazing/ trees):

Agroforestry

Cropland

Annual cropping

Annual cropping - Specify crops:

cereals - maize
cereals - millet
fibre crops - cotton

Number of growing seasons per year:

Is intercropping practiced?

Is crop rotation practiced?

Yes

If yes, specify:

Cotton, maize, millet

3.3 Has land use changed due to the implementation of the Technology?

Has land use changed due to the implementation of the Technology?

No (Continue with question 3.4)

3.4 Water supply

Water supply for the land on which the Technology is applied:

rainfed

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

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. Technical specifications, implementation activities, inputs, and costs

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

• Determination of a contour line using a water level;
• Transferring 03 times the height of 50 cm onto the stakes downstream of the original stake to determine the right-of-way ("apron") of the embankment, which will be 150 cm.
• Fixation of stakes downstream, opposite each projection, but this time graduated at 20 cm for slope determination;
• Opening of an anchoring trench 20 cm deep across the entire delimited area marked by the rope, making sure to dispose of the soil downstream of the bund;
• Placement of stones.

Author:

ProSoil