Furrow Erosion and Water and Soil Management

Abstract

ABSTRACT EFFECTS of basic water and soil interactions on erosion are reported. The effects of flow rate and slope on perimeter shear stress are outlined for channels in which the ratio of breadth and depth of the flow cross section stay reasonably constant. Effects of the resulting shear stress on erosion are discussed in terms of coefficients for the equations developed and several data sets. For furrows with a relatively constant breadth to depth ratio, erosion appears to be related to the shear stress by an exponent which varies between two and four depending on the range of cohesive forces holding the soil particles to underlying soil. The data sets studied indicate continuous exponential relationships rather than a critical shear stress below which there is no erosion. Following disruption of Portneuf silt loam by tillage or compaction, cohesion increases with time. Maximum rate of cohesion increase occurs when the soils are moist, but have sufficient tension in the water to draw the particles firmly together. Rapid wetting of dry soils disrupts a majority of the bonds between particles, allowing aggregate disintegration which reduces infiltration rates and substantially increases erosion. Considering erosion as an independent factor, not affected by sediment load and carrying capacity, allowed development of equations which appear to describe the whole erosion-deposition process. These findings indicate several management options which can decrease furrow erosion.