Soil and water conservation engineering
systems/designs that intercept runoff do not
allow any infiltratationinto the soil but instead,
they collect and convey the water downstream
through a drainage channel. By using vetiver
grass as a green structure, the interest is not in
the diversion of surface runoff as in conventional
engineering design but rather in reducing the
slope length, velocity of flow (runoff) and the
runoff concentration. The green structure forms
a protective barrier across the slope which slows
down runoff and deposits the sediment behind
the green structure (vetiver buffer grass strip).
The structure only filters the runoff and does not
convey it, thus allowing the farmer to enjoy the
full benefits of rainfall as the delay in the flow
when the green structure intercepts the runoff
aids infiltration which is the key to soil and water
conservation. The enhanced infiltration should
improve the water economy within the crop
rooting zone (Oku and Aiyelari, 2011).