"The river is a hundred meters from there."
Translation:De rivier is er honderd meter vandaan.
The er is the unstressed form of 'daar' or there in English. Here's a good explanation of how this er is used: http://www.dutchgrammar.com/en/?n=WordOrder.37. Vandaan just means "from there" in this particular sentence. Ervan means "of it" and that type of er is used differently, see here: http://www.dutchgrammar.com/en/?n=WordOrder.38.