ABSTRACT
These systems are conventionally referred to as surface drainage systems but may, on the basis of their functioning, actually be better referred to as shallow drainage systems. They apply to land in which subsurface drainage systems cannot be used because of the inadequate infiltration or percolation characteristics of the upper soil layers and/or inadequate hydraulic conductivity in the substrata. This situation is typical in so-called heavy land. Representative examples are the basin clay soils of the alluvial deposits, the pseudo-gley soils of mid-and eastern Europe, the planosols of the semi-humid/semi-arid tropics, the vertisols of the semi-arid tropics (black cotton soils) and the glacial till soils, (boulder clays) covering much of northern America, United Kingdom and northern Europe. The prevailing profile characteristics of these soils are shown schematically in Figure 5.1.
