I am currently trying to create a 100m buffer around a stream that would be 1km upstream from a sampling site (that I have as a point) but as the stream flows. I am able to create a 100m 1km buffer as the crow flies (Euclidean distance) using the buffers and clip tools. I want to be able to make a new feature class that is 1km of the stream's distance from the sample point on the river (preferably upstream only). Does anyone have any suggestions of how to do this? And if you do, how do you think it would respond to the river forking at a point of confluence? I am using ArcGIS v. 10.1. Thank you very much for any input you have!