6.7 Technique for creating artificial glaciers in mountain areas

FIGURE 6.7

Technique for creating artificial glaciers in mountain areas

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BOX 6.2

Warping dams

Warping dams are typically up to 5 meters high, but they can be shorter as well. The development of a warping dam consists of two stages: the land development stage and the consolidation and management stage. The land development stage takes several years (on average three to five years, but sometimes more than 10 years). By then, a warping dam will have collected enough sediment for farming to begin. When the warping dam is filled with sediment, stabilization is necessary through the creation of controlled water overflow structures. These structures can be created by changing the existing spillways into a circular shape, redesigning the top of the shaft as a spillway, constructing a side spillway, or designing an earth dam as an overflow dam (van Steenbergen et al. 2011).

guide such meltwater. In this way, poor soils are enriched with fertile fine silt (or warp) or by trapping sediment behind warping dams built on gullies or steep valleys to intercept sediments and thereby create new land terraces (see box 6.2).

Improved Moisture Retention on Hill Slopes The changes that come with road construction are described in the section titled “Changing the Mountain environment” and include opened hill slopes and exposure of the earth to more sunlight and wind. These changes add up to a severe impact on the microclimate that could affect forest stands or the quality of the pasture. The impact on the microclimate will be less water retention, resulting in a loss of moisture, an increase in temperature, and more desiccating effects.

The loss of moisture should be counterbalanced by measures that improve the capacity of the road-affected area to retain moisture, which will also

reduce the risk of erosion and degradation of forest hill slopes and contribute to regreening of the affected area, including potentially compensating for removal of trees during road construction. Large quantities of spoil (rocks and boulders) from road construction provide the material for implementation of these measures. Use of eyebrow terraces or half-moons and stone strips or rock bunds is recommended for steep mountain slopes. eyebrows are small, semicircular, stone-faced structures that open in the direction of the runoff (photo 6.6). They can be built on steep slopes, usually with a maximum preferred slope of 50 percent, yet steeper gradients are possible, especially when rainfall is not torrential. on a slope, the steepest sections should be avoided, and the eyebrows may be constructed in the gentler sections. eyebrow terraces can be complemented by stone strips or rock bunds, particularly on slopes that are relatively even and not too steep (less than 50 degrees). These stone strips will slow runoff, intercept sediment, and build up soil layers. They will stretch over the width of the slopes, allowing water to filter through because they are permeable.

Making Better Use of Excavated Soil Soils are removed when roads are constructed. The construction of a 3.5-meterwide section of road for 1 kilometer with a soil depth of 30 centimeters would

PHOTO 6.6

Eyebrow terraces on mildly sloping land, Ethiopia

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