Even though the river goes through urbanized territory, the water would be brown anyway because the river flows in the Bay of Fundy. The tides there are so strong that twice a day they send a wave upstream called the tidal bore. That wave also carries sediments from the Cap Enragé cliffs (the ones on New-Brunswick's medicare card) up the river, hence all this mud. A Causeway between Moncton and Riverview blocked the flow of the river between 1968 and 2010, had devastating effects but and now that the floodgates are open, the river (and its tidal bore) can be enjoyed by a new generation!
I drew this in november. Actually, if I had seen the river as it is now (first time I've seen it in winter, post-causeway floodgates), I should have drawn it in winter! The tide in the river just won't let the ice sit, plus that muddy water doesn't freeze easily so the sides of the river are continuously re-shaped by the action of water and ice and mud. Where lake Petitcodiac used to sit, early in the morning you can see huge chunks of ice left there by the tide.
Wikipedia insunuates that the very name "Acadie" comes from the Mikmak name of Hall's creek; Panacadie. Truth is, many places in the maritimes had mikmak names that end with -adie. It is safe to say that the creek runs through the heart of modern Acadia though. Even if it's between a freeway and Champlain mall when it meets the Petitcodiac, it runs along the University of Moncton, the George Dumont hospital (biggest hospital to acadians!) and the CBC/Radio-Canada building.
