The erosional impact of soil hydrophobicity: current problems and future research directions

Soil hydrophobicity affects the susceptibility of soils to erosion in a var iety of ways (e.g. increased aggregate stability, reduced infiltration capa city, enhanced overland flow), but there are problems concerning the overal l assessment of its erosional impact. Three current problems are discussed: (I) poor isolation of hydrophobicity from other effects; and poor understa nding of its overall impact: (2) areally, at slope and catchment scales; an d (3) temporally, over periods of months or years rather than on a storm ba sis. These problems are highlighted with reference to the literature and to research in Portugal on highly hydrophobic forest soils. A conceptual mode l relating erosion risk to three key aspects of soil hydrophobicity (tempor al contiguity, spatial contiguity and the thickness of any overlying hydrop hilic soil) is presented in order to provide a framework for future researc h into hydrophobicity-soil erosion Links. (C) 2000 Elsevier Science B.V. Al l rights reserved.