What do you use to measure the gradient of a river?

Question

i remember there was something which you look through to get a straight line and then look along the line at a big ruler =s

Answer 1

It is a Clinometer!

I needed to use one on my Geography River Coursework!

Answer 2

A survey angle tool.  Here is the formula for determining the gradient of a river.

GRADIENT = (ED/HD)  

Elevation Difference (a-c) /

Horizontal Distance (b+c)

a

|

|

|___________c

b