I am trying to replicate a procedure that the USGS Streamstats performs on points delineated along a stream network. They call it the "upstream basin slope" Basically, for a given point that I have confirmed is placed on a stream network, I want to calculate the mean slope of that point's watershed, including hillslopes and channels.
I have a shapefile of around 100 points, all snapped to a stream network (using snap pour points, then manually correcting errors). Many of the points are close to one another (i.e., many points on the same river). I can use the watershed tool to delineate watersheds for these points, but I can't just as easily use something like zonal statistics to calculate the mean slope in each of those watersheds, since the watersheds don't overlap (i.e., the upstream-most points would be accurate, but the rest would have a slope representative of only the portion of their watershed not taken up by the watershed(s) of the point(s) upstream.
Does anyone know of a way to accomplish this task without manually merging together accurate polygon watersheds for every point? I have a lot of points, and it would be extremely time-consuming to perform a procedure point-by-point.