Soil Erosion

Oct
24

Soil Erosion

Africa is a beautiful Continent, a huge mass of brown earth hiding the world’s richest reserves of literally every mineral. However what we so often take for granted is the soil covering and containing this wealth.

Soil erosion is the wearing away of the land surface by running water, wind or other disturbance. Good rainfall will cause water to ‘run off’ roofs, driveways, parking lots etc. The greater the downfall, slope, collection area, the faster and more aggressive the water will flow and be. Soil is bound by vegetation (grass for example). The sparser the vegetation, the easier particles of soil will be collected by the water and moved downstream.

Factors increasing Erosion:

Heavy downfalls, steep slopes, large catchment areas with quick run off.
Sparse vegetation,
Disturbed soil, (building sites), compacted soils (caused by vehicles)
Soil characteristics. Finer soil particles move quicker
Wind of course raises dust storms. These might cause beautiful African sunsets but the reality is that it all depletes the little that is left.

What happens to these particles of soil?

They are deposited elsewhere as sediment. As soon as the velocity of the wind or water slows down, the particles of soil in suspension begin to settle. The heavier particles like gravel will settle sooner and the finer particles will move further away.

The challenges faced.

Sediment causes major problems in South Africa. The incredible dam system built after WW2 are very “silted up” after years of flooding. This means that our beautiful dams carry far less water.

Much of our flood waters flow into the sea. Along the East Coast of South Africa it is well known that when the East wind blows, within minutes the sea will reveal the millions of tons of soil sediment lying on the sand. The water turns green then brown and will only change back to blue when the strong currents are pushed in by the West winds.

In the cities sediment is also a major problem in the storm water drains and any pipe system open to water flow. Another typical example of this is our gutters, at least once a year they should be cleaned of the mud that has collected.

What else can I do?

If your plot is on a steep slope, consider the construction of a retaining wall. This should be backfilled with soil and overplanted with vegetation to slow down the flow of the water. The rule to remember is, the longer and the steeper the flow, the more soil will be lost.
Reduce the slope of your plot. The terms ‘’cut and fill” apply, and once again cover that with vegetation.
Create sediment traps in areas vulnerable to erosion. These can be done with stone, sand bags or other material that successfully slows down the flow of water, allowing sediment to settle where you want it to.
Divert water flow. Instead of allowing water to just run off large roof areas, create trenches which divert and slow down water flow. Grass these water ways. Ensure that the trench is shallow and wide enough to accommodate a lawnmower.
Protect inlets to storm water drainage systems. While we may well say this is a municipal problem, let us remember whose soil is going down the drain and whose taxes will be used to clean those drains. Some believe we should litter to create jobs, but jobs are not free, neither is littering.
A stitch in time saves nine – repair the damage already visible in your space, recover with good top soil, re-grass and Improve Your World.
Have fun – if you need assistance – contact us and we will get a consultant out to your site.