However, if the terraces with sandier soils are high in the catchments, lower erosion loss may be counteracted by the effect of thinner soils. In terms of sustainability there will be a reduced margin of safety, especially in the medium term. Problems may also be compounded because these soils have often suffered substantial previous erosion, have a low fertility status, and the annual cutting back of the riser cannot take place because the risers are supported by walls or rock benches. These are the bari lands that are often marginal in terms of productivity and which support the poorer households. They are also the terraces that suffer most from small-scale landsliding (Gerrard & Gardner, 1999).