The gradient of a river is measured by the number of feet it drops over the course of a mile. This is typically calculated for a given section of river by taking the total drop and the total length of the run for an average drop per mile.
The volume of a river is measured in cubic feet per second (cfs). CFS is determined by calculating the number of cubic feet of water that passes a single point on a river over the course of a second.
Rivers have different styles based on their general dynamics and the type of environment they are in. Some of the reguarly used descriptions included ‘big and bouncy’ (high volume flow and quite free flowing), ‘tight and technical’ (generally lower volume and more constricted flow), ‘pool drop’ (steep section followed by a pool or flatter section of easier flow), ‘continuous’ (ongoing rapids), ‘sustained’ (every rapid are about the same grade), locked in / walled in / gorged out (not easy or sometime not possible to get out and scout or walk around rapids or sections), open (easy to pick and choose what you want to run and get out and look at whatever you want), ledgy (lots of ledges) , read and run (easy to see routes and lines can be easily inspected from your boat on the water rather than the bank), clean (friendly high fun factor / low consequence factor rapids), mandatory (a section that must be run / can not be portaged on a run), pushy (a lot of power in the water which will push you around), polished (slippery rocks which can make inspection and portaging difficult), siphoned (dangerous rock formations in the run), ‘brushy’ (heavy foliaged river banks that can be difficult to get out on, portage though etc), logged /woody (high possibility of trees down in the river), manky (not particularly friendly sections), full (a lot of water / high), full on (challenging / continuous flow of challenging rapids), epic (best quality ever) or epic (full on, very testing, challenging)… the list goes on.
If someone uses a style expression to describe a rapid or river and your not sure what it means ask them and double check its meaning as it can tell you a lot about a run.