Another attempt to “derive ‘ought’ from ‘is’ ” is provided by CamelsWithHammers who identifies “goodness” with “effectiveness” at enhancing the “function” of a being. But his use of the word “function” (rather than something more neutral such as “effect) seems to beg the question by implying value before deducing it.
And in cases where the function of a being is not unique,the goal of enhancing the effectiveness with which a function is performed raises the question of how to weight the competing interests of different functions of the same being.
As an example of this, consider your case of the river.It is effective at several competing functions – transport of precipitated water back to the ocean, carving valleys, filling other valleys and deltas with silt, providing habitat for birds and fishes, etc,etc,etc. Now ask whether drilling a tunnel to bypass a long sweep of the river around a massif (which enhances the water flow at expense of carving), or building a dam (which enhances bird habitat at the expense of some kinds of fishes) is “good for” the river. How can you answer these questions without imposing some relative value on the different functions? And from where can you find that relative value except in your own preferences? (or appeal to authority, the choice of which is really just another expression of personal preference)?