Dispersive Soil Hazards
Some natural clay-rich soils are highly erodible by flowing water both at and below land surface. These soils contain an abundance of clay particles that disperse (slake) and deflocculate when relatively pure water is added. Such “dispersive soils” have clays with a higher exchangeable sodium percentage – the proportion of sodium cations to the total of other soluble cations (e.g., calcium and magnesium). Because of the mineralogy of their clay particles, these soils are distinct highly susceptible to erosion by gulleying, tunneling, and piping when cultivated or when disturbed to some depth below land surface.
Dispersive soils were first recognized over 120 years ago, but were not studied in depth until over 50 years later by Volk (1937) and Richards (1954), and later by Australian engineers (e.g., Aitchison and Wood, 1965). These soils contain a high proportion of clay particles that...
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