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Garden with Insight v1.0 Help: Soil patch next day functions: calculate today's wind erosion

Wind erosion calculation in this model is fairly complex and we won't go into great detail here. There typically isn't much wind erosion on a small garden plot, so it has only a small effect on the simulation.

Wind erosion does not occur if: 1) the option to calculate it is turned off, 2) the wind erosion acceleration factor (a parameter) is zero, 3) there is snow on the soil patch, or 4) the wind speed today was less than 7.5 meters per second.

If wind erosion does occur today, it is calculated in two steps. First, the potential amount of wind erosion is calculated by integrating wind erosion over the course of the day using an assumed distribution of wind speed over the day. The potential wind erosion depends on the mean unsheltered travel distance of wind across the watershed (a long thin watershed has more wind erosion than a square one), soil water content in the top soil layer (dryer soil = more wind erosion), and a soil patch parameter for the mean size of soil particles (smaller particles are easier to blow away). Remember that each soil patch in this simulation has its own watershed, as if it were in its own separate valley.

The potential wind erosion for today is reduced by multiplying it by several factors that range from zero (no wind erosion) to one (no reduction from the potential amount). The factors are as follows.
gif/20000000.gif The soil erodibility factor is based on the relative proportions of sand, silt and clay (the soil texture). Roughly, the more sand the greater the wind erosion.
gif/20000000.gif The surface roughness factor has to do with the roughness of the surface of the soil. Soil ridges tend to protect the soil from wind erosion, depending on which way the wind is blowing. The orientation of the soil patch is compared to the wind direction for the day to determine sheltering or exposure of the soil to wind.
gif/20000000.gif The vegetative cover factor is based on the amount of live and dead plant matter on the soil. Soil cover tends to reduce wind erosion.
gif/20000000.gif The coarse fragment factor reduces wind erosion based on rocks in the surface soil layer.

EPIC Wind erosion
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Updated: May 4, 1998. Questions/comments on site to
Copyright © 1998 Paul D. Fernhout & Cynthia F. Kurtz.