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City of Winona MN

The city of Winona is often considered to sit on the Minnesota side of the Mississippi River. Because of an eastward bend in the river, Winona is generally south of the Mississippi at this location. The photo below left includes one of Winona's most famous landmarks, Sugarloaf. This is a bluff that in addition to many stories from native Americans provided a substantial rock resource to the city of Winona. The bluff was one of the earliest quarries in the area and so much rock was mined that the top of the bluff was nearly gone. The remaining part has a shape similar to a loaf of bread which became the source for the name.

The elevation changes drastically in a short distance near Winona. In the photos below it looks like the buildings and trees are growing up right out of the middle of the river. In reality, the City of Winona is in the Mississippi River. During the last glacial age the water was up to the top of the bluffs and also ran much deeper than the Mississippi does today. As the flood waters from the glacial melting slowed down the bottom of the river valley accumulated sediment and started to fill it up. Drill tests indicate that the sediment has filled in about 300 feet of river bottom, or about 1/3 the depth of the original maximum of the river. The island that is Winona is part of these sediments. There is no "empty" land for development in Winona so most of the new building is taking place on top of the bluffs. Even parts of the river are used for building as some houses literally float in the river, tied by water and electrical utilities to the shore. In 1955 almost the entire city of Winona was underwater from the Mississippi flooding. After the 1955 flood dikes were put up around the edge of the river to hold back floods so now the Wisconsin side floods because the Winona dikes are just a little higher.

A similar sedimentation effect cause another Mississippi River feature that is known to most Minnesotans called Lake Pepin. Lake Pepin is just a wide shallow area of the Mississippi River that has a southern end where the Chippewa River from Wisconsin empties into the Mississippi. Lake Pepin was formed by a pile of sediments deposited in the Mississippi channel by the Chippewa River. This deposit of sediments at the end of a river is called an alluvial fan. Fans are formed most typically in lakes and oceans as fast moving river water empties into the larger body of still (or in the case of the Mississippi River slow moving) water. When the water velocity decreases the ability to carry sediment (load capacity) decreases and much of the sediment settles out.

The photos below are taken from Garvin Heights Park almost 500 feet above the river. The park is on Oneota Dolomite, the last part of rock Formed during the Cambrian time in this area.

The "lake" in the lower part of the left photos is dredged to keep it deep enough for swimming and other recreational activity. It is an oxbow lake, what used to be a meander (a bend) in the river before erosion cut it off from the normal flow.

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