I am trying to figure out if there is a way to calculate area on a line (river) between two points (dam) for an entire watershed. In a way I want to make a corridor of where fish are able to move freely between dams. Any suggestions are appreciated!

[KatelynVardy]

I am trying to figure out if there is a way to calculate area on a line (river) between two points (dam) for an entire watershed. In a way I want to make a corridor of where fish are able to move freely between dams. Any suggestions are appreciated!

[JoeBorgione]

By definition, a line only has length.  Using linear geometry to model rivers, streams, and canals is a common practice but clearly has it's limitations. If the data exists, you could model your streams using a linear reference system approach where reaches are given a width. Very data intensive.  You could also buffer the lines with some sort of average width and find area that way. Just to toss another challenge at you, shouldn't channel depth and or morphometry  be considered as well?