An Ecological Assessment of the Louisiana Tensas River Basin Chapter 3 
Soil Erodibility Analysis 
Soil erosion is important because it reduces productivity 
of agricultural lands and because eroded soil can be 
transported to a stream where it becomes sediment. 
Topsoil is expensive to replace and natural soil-forming 
processes would require thousands of years to replenish 
soil already lost from the Nation's farmland. One of the 
tools developed by agricultural scientists to estimate soil 
loss from farm lands is the Universal Soil Loss Equation, 
or USLE. The USLE is intended to demonstrate how 
agricultural practices contribute to or reduce soil erosion. 
The USLE is not generally applied to nonfarm land cover 
types. 
Figure 3.22 shows the watershed classes for the different 
USLE K-factor erodibility values assigned to the surface 
soil horizons. The K-factor estimates the relative erodibil¬ 
ity of a soil with respect to all possible textures (range 0.0 
to 0.64). Surface soils in the Tensas River Basin exhibit 
K-factors ranging from 0.18 to 0.48. As shown in the 
figure, the most erodible soils seem to occur most com¬ 
monly in old oxbows and meander channels and are 
spread evenly throughout the Basin. The least erodible 
soils occur in backswamp areas adjacent to active 
stream channels. 
K-factor 
; Water 
0.18- Low 
0.21 
0.27 
0.28 
0.29 
0.3 
0.31 
0.32 
m 0-35 
0.38 
0.4 
0.41 
0.45 
0.48-High 
Figure 3.22 
Relative Soil Erodibility Map for Tensas River Basin. 
Source: NRCS STATSGO. 
