I want to to do the following thing: I want to create NoData if the change of the slope angle between cells is >30%But I dont know what I have to do to realize it.
The cutoff slope angle is defined as the change in slope angle from one cell to the next along the flowdirection. This value ranges from 0 to 1 for all areas where the slope angle decreases from one cell to the next (if the slope angle increases, there will definitely be no deposition). Therefore, the user input value will range from 0 �?? 1 and be dependent upon the amount of sediment carried by overland flow. For example, an input value of zero will cause the slope length to reset every time there is a decrease in slope angle. An input value of one will cause the slope length to never reset. In an ideal world, this value would be set by an expert familiar with the particular area in question. However, this is not always feasible. The literature(Griffin,et al., 1988; Wilson, 1986) suggests references that a value closer to 0.5 (slopedecreasing by 50% or greater) is appropriate.
Jeffrey Evans:How to calculate changes in slope angle between cells/areas?The original USLE assumed little slope curvature and no deposition. To account for flow convergence in complex terrain, modifications were made to the LS factor with an equation that incorporates flow accumulation. Because they are now used interchangeably, when you see reference to slope-length most likely it is in reference to the LS factor, as calculated below.To calculate the LS factor for the RUSLE equation, first calculate flow accumulation (facc) and slope in degrees (slp). Then a bit of map algebra in the raster calculator yields LS.Power(facc * cell resolution / 22.1, 0.4) * Power(Sin(slp * 0.01745) / 0.09, 1.4) * 1.4 One downside of the stack exchange is they do not promote discussion - they just want the answers! So may I ask you, Markus, to follow up the post when you have figured out how to do this. I am especially interested in whether the Curvature tool (which is designed to capture this deposition/erosion factor for modeling) was any use to you in parameterizing USLE. I'm sure the Spatial Analyst team would love to hear what you think, especially if you have a idea on how to improve or complement that tool.
The original USLE assumed little slope curvature and no deposition. To account for flow convergence in complex terrain, modifications were made to the LS factor with an equation that incorporates flow accumulation. Because they are now used interchangeably, when you see reference to slope-length most likely it is in reference to the LS factor, as calculated below.To calculate the LS factor for the RUSLE equation, first calculate flow accumulation (facc) and slope in degrees (slp). Then a bit of map algebra in the raster calculator yields LS.Power(facc * cell resolution / 22.1, 0.4) * Power(Sin(slp * 0.01745) / 0.09, 1.4) * 1.4
Power(facc * cell resolution / 22.1, 0.4) * Power(Sin(slp * 0.01745) / 0.09, 1.4) * 1.4
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