I have line file which represents rivers and a polygon file which represents vegetation. I need to what distance of each river runs through each type of vegetation. I believe this is similar to the Spatial Join feature however a Spatial Join is not going to tell be the distance a river is within each vegetation polygon. Do you know how I can calculate type of spatial join?
Intersect your lines to vegetation which will break up the lines to what falls inside the vegetation polygons. If you need some attributes transferred from the vegetation layer, you would then run the spatial join with the layer created above and your vegetation. Finally, simply calculate the length of the lines that fall within each vegetation polygon.