Morning

Am needing help with a particular task; that of working out a rivers catchment area.  I could do it on a paper map but would rather the ability to quickly alter data and have it updated without drawing it all over again etc.

The tasks I need to complete are using a map with contours as a dwg file (I have).

• I need to draw a line that crosses each contour at 90 degrees.
• Once done I need to then measure the area of resulting polygon.
• I then need to measure length of river, already on the map but in four parts (needs to be considered one complete line).
• I also need the points (length from start) of where the river crosses each contour line.
• I then need to draw out another polygon and measure it’s area.

Would love some basic steps explained as how to complete the above and if there even possible.

Many many thanks, Matthew