In a non-scenario game, your city's founding tile must be adjacent to a forest or river (diagonally adjacent works) to build a logging camp or pier. In the scenario, you can build towards a forest or river that's 2+ tiles away from your founding tile, and then construct a logging camp or pier when adjacent. But, this only works if you have not saved and then loaded the game yet (loading from autosaves has the same effect as loading from custom saves).

Also, there's a fake river to the south of the Yithril Invasion Force's city (next to where they build a second city if you let them).