How to Fight Soil Erosion

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How to Fight Slopes Soil Erosion?

Short Description

• Problem: Due to deforestation or poor agricultural managment, the soil layer is being washed down by rain, causing gullies, poor agricultural conditions, and a risk for the populations.
• Idea: Slowing the speed of the rain water on the slope, filtering the soil from the water and causing the particles to stay on the slope, planting deep roots plants or trees stabilizing the soil deeply, working on the horizontal contour lines.
• Difficulty: Often huge surfaces concerned with the problem, work intensive solutions, necessity of an general agreement on the works within the community, maintainance.
• Price Range: Accordingly to the labour intensivity, expensive
• Material Needeed: Deep root trees and plants, construction material
• Geographic Area: Global
• Competencies: Understanding of contour lines, construction and planting skills
• How Many people? From 5 to a community
• How Long does it take? Depending on the slope and area concerned. labour intensive.

Description

The basic principles of the fight against slope erosion are to stabilize the soil through the planting of trees like or deep rooted plants like vetiver, working on the horizontal contour lines to slow the speed of the rain water on the slope, which as a midterm side effect improves the water infiltration and the groundwater levels, and to filter the washed soil particles from the flowing rainwater.
On relatively flat slopes, it will already be of some help to plough perpendicularly to the slope, along the contour lines.

Contour lines are (abstract) lines that follow an horizontal path along the hill or the mountain side. They are perpendicular to the slope. Some animals create such horizontal paths: thoses paths can be an indication to recognize a contour line. An A shaped wood frame with a weighted string attached to the top angle, and a point marking the middle of the horizontal beam can be helpful to mark precisely horizontal contour lines: when the string hangs centered on the mark, the two legs of the A are at the same horizontal level.
Some of the traditional ways to fight soil erosion is the creation of walls or fences along the contour lines. You should consider the fact that the pressure of the rainwater flow can break the wall or at least strongly weaken it, and that there should always be a sufficient drainage to lower the pressure. Planting vetiver is a promising alternative to walls and fences as it allows the water to flow through but filters efficently soil particles and is quickly deeply rooted. Reports show that in the course of the time, natural terrasses create where vetiver was planted. It is important for terrassing walls or vetiver contours that no opening occures in the contour, that those elements are undisrrupted along the contour line, for this would mean an increased flow of water destroying parts of the construction and creating a gully.

Contacts

• WOCAT: World Overview of Conservation Approaches and Technologies.

CDE WOCAT Hallerstrasse 10 CH - 3012 Berne Switzerland Tel.: ++41 31 631 88 22 Fax: ++41 31 631 85 44 New Email-Address: wocat (at) cde.unibe.ch http://www.wocat.net

Links

Link to Fourthway's poster "How to stop soil erosion": http://www.fourthway.co.uk/posters/pages/soilerosion.html

Link to Fourthway's poster "Why Mulch?": http://www.fourthway.co.uk/posters/pages/mulch.html

Bibliography

Pdf on evaluation of invasiveness of Vetiver in Fidji, Paul Truong & Colin Creighton

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