1) Detroit River 2) Downstream 3) Toward the mouth 
Downriver is the unofficial name for a collection of 18 suburban cities and townships in Wayne County, Michigan south of Detroit along the western shore of the Detroit River. The name derives from the fact that the Detroit River, after running more or less west along the banks of Detroit and Windsor, Ontario, then bends to flow largely south befor...
[adv] - away from the source or with the current
downstream adverb away from the source or with the current
with or in the direction of the current of a river: logs floating downriver.