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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

Drop structures

Drop structures are constructed to slow the flow of water in channels. In a steeply sloping channel, erosion can be controlled by allowing the water to flow over a series of steps, or drop structures. Though effective, these structures are quite expensive for ordinary farmers to construct. Drop structures are more effective when combined with check dams. They can also be reinforced by vegetative means, such as planting trees or shrubs.

Advantages

· Controls the upstream water velocities to reduce erosion.
· Drops the water flow to a lower level.
· Dissipates the excess energy of water flow.
· Controls downstream erosion.

Limitation

Requires some skill to construct.

Factors affecting adoption

Biophysical

Drop structures built of wood may rot over time; it may be necessary to use preservatives.

Socioeconomic

· Expensive to construct when materials other than logs or stones are used.

· Complex designs using concrete require skill to construct.

· Unless the causes of the excessive upstream runoff are also addressed, the drop structure will not be effective over the long run.