I am new to ESRI products (I typically use QGIS), but am using it in order to analyze upstream/downstream flowlines with the National Hydrography Dataset (specifically, HUC-4 mapping units for NHDPLUS HD data). In particular, I am hoping to select all upstream and then downstream flowlines from a polygon layer. An example might be - what are the upstream flowlines that flow into this state park? It seems like the only way to do this is the trace upstream flow accumulation by point (by dropping a flag). This will be prohibitively cumbersome to try and drop a flag at all of the points the polygon boundary intersects with NHD flowlines.
Is there a way to set the starting point from the polygon object itself? I have state parks in one layer, and NHD flowlines in another. My ultimate goal is to be able to identify upstream/downstream monitoring stations (which is a point layer of water quality monitoring stations).