#202Runoff barriers

Applicable for:

Arabica, Robusta

202⸱AConcept

Reduces erosion
Improves water infiltration
Balances soil humidity

Steep slopes combined with heavy rainfalls that are happening more often due to climate change raise the risk of heavy downhill currents and erosion. Creating barriers across slopes and streams can slow down the water flow. This helps to improve water infiltration and reduces erosion and the leaching of nutrients.

Barriers can be

artificial dams and drop structures,
stone or vegetative barriers that form terraces on the hillside,
swales, as shallow, broad, vegetated channels.

These barriers help to form retention basins or infiltration zones that capture the excess water so that it can seep into the ground and replenish the groundwater. In this way, this relatively simple method can solve the problem of both too much and too little water.

Another measure to prevent erosion and recharge the groundwater with an immediate effect on less steep plots is the tool of Rainwater basins. This is, however, rather recommended in cases of emergency and not as a long-term solution.

202⸱BTo be considered

Timing: Barriers can be built at any moment. Building them before planting coffee trees facilitates the construction of barriers and reduces coffee tree damage. If combined with vegetation, the growth time of the plants should be considered. Barriers are particularly valuable after longer drought periods and when there is a risk of strong rainfalls.

202⸱CImplementation

202⸱1Procedure

For hillsides with >30 % slope:

Create barriers

Build barriers with stones, soil or other inert material transversely to the slope of the terrain. This compacts the soil and prevents its erosion by slowing down the speed of water during rains.

Where gullies have already formed in the ground due to heavy rainfall, line them with stones or bags of sand or soil. This will dampen the impact of the falling water, reduce the flow velocity, and slow down further erosion.

202⸱2

Plant vegetative barriers

Cover plant strip

a row of plants growing on the side of a hill .

Plant perennials and dense-growing plants such as elephant grasses, vetiver, lemongrass, or German iris as living barriers perpendicular to the slope. They slow the water flow and reduce erosion and the likelihood of flooding. They also increase infiltration and reduce runoff into streams. Sediments or particles that are removed by water currents are deposited in these barriers.The steeper the slope, the closer the living barriers should be.

In coffee areas that have been terraced, barrier plants are planted on the edge of the terrace to prevent the terrace from sliding.

Tip

In areas of high rainfall, it is recommended to plant the barriers with a gradient of 0.5 to 5 %. This means that the level line that is drawn to plant the coffee and the live barriers, will have a slight gradient. This ensures good drainage and avoids waterpuddles. At the same time, the draining is so smooth that it prevents soil erosion.

202⸱3

For streams through or near the coffee plots:

Create an artificial dam and drop structure

Place tree branches across the stream and firmly secure them with vertical posts. This will create a partial dam.

Line the area below the dam with rocks to create a catchment basin. The water will drop one to two meters into the basin below, reducing its velocity.

Repeat periodically along the stream. A number of these drop structures will be needed along the length of the stream as it passes through or near the coffee plots.

202⸱DEconomic benefits

Lower renovation costs 

This tool increases the lifespan of the coffee trees. They need to be renovated less frequently which reduces the long-term production costs.

Higher coffee yield

The effects of this tool can lead to a higher coffee yield and therefore a higher income.

202⸱EGreen benefits

Better soil life

This tool helps improve soil life (microbes, earthworms, etc.). This plays a vital role in plant nutrition and contributes to a healthy ecosystem.

202⸱FFurther readings

Documents

PDF

Info Sheet Rainwater Harvesting by Basins Tanzania

Links

BARROS, L. C. de et al. Integração entre Barraginhas e Lagos de Múltiplo Uso: O Aproveitamento Eficiente da Água de Chuva para o Desenvolvimento Rural, Circular Técnica, Sete Lagoas, 11p. 2013.