Sagan 4's current map is so mountain-dominated that there's a sharp elevation change going down rivers to their estuaries. In real life, this would create canyons. Given how long many of our rivers have existed, one could even argue that Sagan 4 has a Grand Canyon for every one of them.
If this is the case, would it be fair to treat all riparian biomes that cut through moutains as though they include cliffs on either side?