Description
Similar names: Banquettes, boomerangs, terraces, stone bunds, eyebrow systems, eyebrow basins.
Eyebrow terraces are a form of micro-catchment water harvesting system. They are handmade microbasins, in the shape of an eyebrow, and are often made from soil and stones. Their main goal is to facilitate vegetation growth on steep slopes by collecting runoff water from a small catchment area and have it infiltrate the soil. This way, it is stored in the root zone and will be available for crops. They are usually situated on hillsides and can be used on slopes of up to 50%. The steeper the slope, the more the bunds have to be reinforced with stones. Eyebrow terraces work well in areas characterized by 200-600 mm of annual rainfall. Reinforcing eyebrow terraces with stones on steep slopes makes them more resistant to the increased water speed caused by the slope. Instead, they can be some meters apart. After completion, the pit uphill from the eyebrow may fill with sediments and soil, thereby giving rise to terraces.
PRE-CONDITIONS FOR IMPLEMENTATION
- Maintenance: the eyebrow terraces need to be maintained as they can break especially the first few seasons after a heavy rainfall.
- The cost of the implementation can be quite important if there are no stones available in the area.
METHOD OF APPLICATION
Eyebrow terraces are usually built by scraping soil and stones together and putting them in place to form a ridge. The center of each pit functions as a great location for a tree. The catchment area (or the area of the micro catchment intervention, in this case the Eyebrow terraces) should always be larger than the cultivated area, in order to be able to collect sufficient water for the crops. The ratio between the catchment area and the cultivated area can vary between 2:1 and 10:1. For an eyebrow terrace intervention, if the cultivated area is 1-5 square meters, the catchment size should be at least 5-50 square meters. Useful indications about the spacing and dimensions of Eyebrows terraces can be found here.
BENEFITS & COSTS
This intervention contributes to:
CASE STUDIES
Morocco:
Perma Atlas offers a very good example of eyebrow terraces, or as they call them, “boomerangs”. Click here to know more about their projects.
Ethiopia:
Eyebrow terraces result most suitable where there are many stones present in the area, as this example from Ethiopia illustrates.
