Erosive effects of the large water drops (gravity drops) that fall from plants

Abstract

A large proportion of rainfall, intercepted by plants, is released again as large 'gravity drops', averaging about 5 mm in diameter. Almost all raindrops are considerably finer, and less erosive, than these large drops, and such conversions can thus result in increased drop erosivity. Because all are large, fall height provides the major control of gravity-drop erosivity. Experimental studies demonstrated that erosivity rose rapidly over the first 2 m of free fall, and it was found that only drops released from less than 0.3 m above the soil surface had small-to-negligible erosivity. Conversion of some 15-20% of a fine, artificial rain to gravity drops by a small tree branch, held only 0.8 m, above a shallow water flow, more than tripled the transport rate of medium sand.