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close this bookResource Management for Upland Areas in Southeast Asia - An Information Kit (IIRR, 1995, 207 p.)
close this folder3. Soil and water conservation approaches
View the documentIntroduction to soil and water conservation approaches
View the documentBench terraces
View the documentComposting
View the documentContour tillage/planting
View the documentCover crops
View the documentCrop rotation
View the documentDiversion ditches
View the documentDrop structures
View the documentGrass strips
View the documentHedgerows
View the documentMinimum tilIage/zero tillage
View the documentMulching
View the documentRidge terraces
View the documentShifting cultivation
View the documentSoil barriers
View the documentSoil traps
View the documentWater harvesting

Soil traps

Soil traps are structures constructed to harvest soil eroded from the upper slopes of the catchment. The most common types of soil traps are check dams and trenches, built in diversion ditches or waterways.

A check dam slows down the water flow and allows heavier soil particles to settle. The size of the check dam depends on the size of the drainage or gully to be protected. Check dams can be built of Gliricidia stakes, bamboo, loose rocks, logs or other locally available materials.

Trenches are built to trap soil along the waterways and complement the function of check dams. A trench is dug about 1-2 meters above the check dam, at least 0.8 m deep, 1.0 m long and 0.5 m wide. A variation is to construct the trench at the lower portion of the field just above a bund. The purpose is to trap soil and to store water temporarily to increase infiltration.

The accumulated soil in trenches and dams is returned to the field.


Soil traps (A)


Soil traps (B)

Advantages

· Prevents widening and deepening of gullies.
· Promotes the deposition of nutrient-rich, highly fertile sediments.
· Reduces the velocity of runoff in gullies.
· The area where soil accumulates can be used for growing crops.

Limitations

· Requires continuous desilting to prevent overtopping during heavy rains.
· Check dams require regular repair and maintenance.

Factors affecting adoption

Biophysical

Materials for making check dams may be unavailable.

Socioeconomic

Damage to check dams must be repaired and trenches desilted frequently.
Soil traps constructed without the necessary support structures may be ineffective.

Prepared by Kennedy Igbokwe