Effigy Mounds National Monument follows along the Mississippi River on the east side and is split by the Yellow River in the center of the monument.
The channel of the Mississippi River is heavily used for commercial navigation and recreation the riverbed serves as the home of many species of mussels. The federally endangered Higgin’s eye pearly mussel is holding on in spite of exotic species invasion by the zebra mussel. For many years sedimentation reduced the population from most of its original range. Today, the Higgin’s eye pearly mussel and other native mussels may face extinction due to the proliferation of zebra mussels and habitat degradation. Eastern spiny and smooth softshell turtles use the channels and are also declining in numbers.
The Yellow River gets its name from the muddy banks and clay laden waters that flow into the Mississippi River. Several miles upstream, the river actually flows over rocky riffles and meanders through pastures and woods. During the 19th century, the Yellow River was used to power several mills due to its rapid drop from the headwaters. Many springs and tributary streams flow into the Yellow River. The riparian habitat of the Yellow River extends several miles from the river’s mouth through the valley to the west. The terraces above the floodplain contain alluvium, a fertile soil that grows large black walnut and many other nut producing trees.