Big Muddy River Southern Illinois with "loess", fine grained, wind born deposits. At the edge of the floodplain, dunes, called "loess hills", formed. The Pine Hills are loess hills standing several hundred feet above the floodplain. Prior to the construction of Rend Lake, much of the ancient lake bed was swamp: a forested area that was covered by water through most of the winter, and during wet summers. When the Big Muddy flooded, the water covered the flat bottom of the ancient lake bed for miles either direction from the meandering channel. The upper reaches of the Big Muddy are near Dix, Illinois.
Muddy River (Massachusetts) flows through a conduit under Route 9 and into a narrow park called the Riverway, from which it flows through three culverts: the Riverway Culvert, the Brookline Avenue Culvert, and the Avenue Louis Pasteur Culvert. The Muddy River continues from the Fens toward its connection with the Charles River via the Charlesgate area, running through a stone-paved channel surrounded by a narrow strip of parklands. In a series of stone bridges and tunnels, it passes under Boylston Street, Massachusetts Turnpike, Commonwealth Avenue, Storrow Drive, and a series of elevated connecting ramps (the Bowker Overpass). In its natural state, the outlet