That BMP is a “practice” and it is to, whenever possible, Reduce the Amount of Disturbed Area During the Rainy Season. Therefore one of the MOST effective BMP is what I call the ‘thinking persons” BMP, which is a do-nothing BMP. This is usually an anthropogenic (human-caused) land-use problem. The prerequisite for Raindrop Impact Erosion is laying the soil bare by removing the soil cover. Remember the axiom “Less runoff from a site correlates to less discharge and less discharge greatly reduces the likelihood of receiving a regulatory action!” He can then slowly infiltrate into the soil. Now envision Junior landing on grass or nice soft Mulch, making a cushion for his tush. But “good parents” will slow Junior down by roughening the soil surface and putting slope interrupters, like fiber rolls down across the slope/ Junior loves it when we leave the soil surface smooth and hard. That is why, in practicing good erosion control, we are being like good parents and not letting Junior get going too fast. Junior will then get a bad attitude and begin running off! That is how rills start. Note that Sheet Flow doesn’t have much excess energy to needed to dislodge – for that the energy comes from raindrop impact energy.Įnvision Junior raindrop hitting bare soil and causing the explosion all the while it also hurts his tush. That raindrop erosion energy causes the first detachment and breakup of soil particles, and now that soil surface ready now for transport and delivery from sheet flow (sheet erosion). It is this energy (Raindrop Impact) that detaches and dislodges soil particles, by a magnitude, at least, over tractive forces of flowing water erosion (Rills, Channel Bank, Bed, and Gully Erosion) My physics professor in college demonstrated that the raindrop, average size 1cm 3, shaped to minimize friction, need only fall about 30-ft to reach maximum velocity. You know, the energy from a falling raindrop onto bare soil is like a bomb!! Or actually millions of little bombs during a decent storm. I often inform my students that an estimated 90% of the erosion in the world is caused by raindrop erosion. The “Big Four” Erosion Control (raindrop) BMPs
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