Historic Mill Creek!
Flooded oxbows where river cut through old dunes and sand deposits overlaying subcrops of sedmentary bedrock. The bedrock, being near the surface, diverted the energy of the river from cutting downward to cutting sidways. First creating big river bends and then cutting through the narrows and creating oxbows. The Ninth Street Dam flooded this network of oxbows, stopping the active bank cutting and creating a series of curving linear island and emergent wetlands.