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3 <br />Table 1: Erosion severity categories. <br />Symbol Category Lateral Recession Rate (ft/yr) <br />ammo Slight 0.01-0.05 <br />Moderate 0.06-0.2 <br />Severe 0.3-0.5 <br />Very Severe >0.5 <br />Description <br />Some bare bank but active erosion not readily apparent. Some rills but no <br />vegetative overhang. No exposed tree roots. <br />Bank is predominantly bare with some rills and vegetative overhang. Some <br />exposed tree roots but no slumps or slips. <br />Bank is bare with rills and severe vegetative overhang. Many exposed tree <br />roots and some fallen trees and slumps or slips. Some changes in cultural <br />features such as fence corners missing and realignment of roads or trails. <br />Channel cross section becomes U-shaped as opposed to V-shaped. <br />Bank is bare with gullies and severe vegetative overhang. Many fallen trees, <br />drains, and culverts eroding out and changes in cultural features as above. <br />Massive slips and washouts common. Channel cross section is U-shaped and <br />stream course may be meandering. <br />Soil Loss Estimation <br />Any section of riverbank identified as either severe or very severe was included in a site <br />profile for more detailed analysis. The analysis consisted of calculating the following <br />variables for every section of severe or very severe erosion (Appendix B). <br />• Depth (D): horizontal distance from the toe to the top of the bank; <br />calculated using GIS <br />• Height (H): vertical height; measured with November 2011 <br />LiDAR elevation data using GIS <br />• Slope Length (SL): length of diagonal slope; calculated <br />using depth and height measurements <br />• Recession Rate (RR): annual lateral recession of bank (0.4 <br />ft/yr for severe erosion and 0.75 ft/yr for very severe <br />erosion) <br />• Length (L): length of the erosion along the river; <br />calculated using GIS <br />These variables (Figure 1) were used in the equation below to <br />estimate the annual soil loss. Sandy soil weighs approximately <br />100 pounds per cubic foot. <br />AZ) <br />Recession <br />Rate <br />11 <br />Bank <br />Cross -Section <br />Depth <br />Figure 1: Diagrams of variables used for soil <br />loss estimation. <br />SL(ft) * 1J1z(ft / yr) * L(ft) * 100(lb / ft3) Estimated Soil Loss <br />2000(lb / ton) (tons/year) <br />Equation 1 <br />Atlas Generation <br />All of this information was used to create an inventory atlas of the pool which can be found in Appendix <br />A. The atlas contains erosion severity and photos of the shoreline. <br />