Riparian zone: streambanks, often flooded but generally well-drained.
Typical soils: nutrient-rich immature soils (eutrudepts) and more organic variants (hapludolls); on relatively recent floodplain deposits (alluvium).
Typical native trees: include sycamore, box-elder and American elm, but often mixed with species more typical of the uplands; silver maple is more common along larger streams below the park
Native shrubs: include elderberry, dogwoods and willows.
Native grasses and wild-flowers: Some common species can easily spread by seed: e.g. wild-ryes (Elymus macgregorii), phacelias (Phacelia purshii), alexanders (Zizia aurea), lowland coneflower (Rudbeckia lacinata). Rarer species can be more gradually introduced over the years: e.g. reed-grass (Cinna arundinacea), fringed loosestrife (Lysimachia ciliata), lowland beebalm (Monarda “serotina”).
For more details: “Riparian Bluegrass” at bluegrasswoodland.com.
See also “Riparian Forest” of KY Nature Preserves; but that is a broad class that includes more acid or infertile soils with river birch, and larger along streams with more silver maple, cottonwood and willows.