The Fourmile Creek Watershed is located in the Des Moines Lobe landform region, near the
southern terminus of this lobe that formed during the Wisconsin Glaciation between
12,000 and 15,000 years ago. Glacial activity, other climatic events, and land use practices that followed the last glaciations have shaped the landscape, contributing to carving a more defined Fourmile Creek stream channel. This region has mostly level terrain and occasional bands of crooked ridges. Marshes and ponds are found between these ridges and generally, have no natural drainage outlets. The landforms found in the watershed are ground moraines on uplands, and flood plain and stream terraces. As a result, the upper portions of the watershed have pothole characteristics, which provide depressional areas that pool runoff and help regulate flows. The lower portion of the watershed is characterized by a gently to moderate rolling landscape, such as in the Des Moines, Altoona, and Pleasant Hill areas.

Land Use

Primary land use varies across the Fourmile Creek Watershed.

  • The upper, northern section of the watershed is primarily agricultural, consisting of
    cultivated row crops and small amounts of pasture and hay. The area is rural with a
    small amount of development.
  • The middle section of the watershed is approximately half agricultural, cultivated
    crops, pasture, and hay. The other half of this portion of the watershed is urban
    with low, medium, and high-density development.
  • The lower, southern section of the watershed is primarily urban with low, medium,
    and high-density development. It also consists of a small amount of deciduous
    woodland, pasture hay, and cultivated crops.
The bedrock of the Fourmile Creek watershed consists of marine sedimentary rocks deposited over 350 million years ago