Missouri River floodplain

Missouri River floodplain
Name	Missouri River floodplain
Location	Missouri River, Missouri, Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas

Missouri River floodplain The Missouri River floodplain spans extensive riparian landscapes along the Missouri River across the Great Plains of the United States, influencing settlement, transport, and ecology from Fort Benton, Montana to St. Louis, Missouri. This floodplain interconnects with major tributaries such as the Platte River, Mississippi River, Kansas River, Yellowstone River, and Big Sioux River, and has shaped the development of cities including Omaha, Nebraska, Kansas City, Missouri, Bismarck, North Dakota, Sioux City, Iowa, and St. Joseph, Missouri.

Geography and extent

The floodplain extends through the Missouri River basin and crosses state boundaries of Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri, encompassing low-lying terraces, alluvial islands, and oxbow lakes near confluences with the Platte River, Niobrara River, James River (South Dakota), and White River (South Dakota and Nebraska). Key geomorphic features occur adjacent to navigation hubs like St. Louis, Kansas City, Missouri, Sioux City, Iowa, and historic ports such as Fort Benton, Montana and Bismarck, North Dakota, while federal designations and management involve agencies including the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and National Park Service.

Geological and hydrological formation

The floodplain formed through Pleistocene and Holocene alluviation tied to glacial meltwater from the Laurentide Ice Sheet and fluvial processes influenced by the Mississippi River system and tributaries like the Yellowstone River and Platte River. Sediment deposition created terraces, point bars, and meander belts documented in studies by institutions such as the United States Geological Survey and University of Nebraska–Lincoln. Hydrology is driven by snowmelt in the Rocky Mountains, runoff from the Bighorn River and Tongue River, and regulated by reservoirs like Fort Peck Lake, Garrison Dam, Oahe Dam, and Gavins Point Dam, which altered seasonal flow regimes studied by researchers at Iowa State University and Montana State University.

Ecology and habitats

The floodplain supports floodplain forests, cottonwood galleries, willow carrs, tallgrass and mixed-grass prairie remnants, wetlands, oxbow lakes, and backwater sloughs that provide habitat for species monitored by Audubon Society, The Nature Conservancy, and the U.S. Fish and Wildlife Service. Iconic fauna include migratory birds along the Central Flyway such as Sandhill crane, Whooping crane recovery efforts, and shorebirds that use sites like the Cheyenne Bottoms and Loess Bluffs National Wildlife Refuge (formerly Squaw Creek NWR). Aquatic communities include Pallid sturgeon, Shovelnose sturgeon, Channel catfish, and native mussels protected under listings by the Endangered Species Act and agencies such as the National Marine Fisheries Service.

Human use and cultural history

Indigenous peoples including the Lakota, Omaha (tribe), Ponca, Otoe–Missouria Tribe of Indians, Mandan, Hidatsa, and Arikara Nation relied on floodplain resources, trade routes along the river used by explorers like Lewis and Clark Expedition, and sites associated with treaties such as the Fort Laramie Treaty. Euro-American settlement accelerated with steamboat commerce tied to entrepreneurs like Augustus Le Plum and riverports in St. Louis, Bismarck, and Fort Benton, and later rail corridors by the Union Pacific Railroad and Atchison, Topeka and Santa Fe Railway. Agricultural conversion to cropland and pasture by settlers, incentivized by policies like the Homestead Act, reshaped floodplain landscapes and displaced many Indigenous communities.

Flood management and river engineering

Flood control and navigation projects by the U.S. Army Corps of Engineers, prompted by landmarks such as the Great Flood of 1993 and earlier 19th-century floods, produced infrastructure including levees, revetments, bank stabilization, and the Pick–Sloan Missouri Basin Program featuring Garrison Dam and Oahe Dam. Navigation improvements created a maintained channel for towboats serving ports at Kansas City, St. Louis, and Sioux City, with locks and dams modeled after projects on the Mississippi River. Controversies over projects involved stakeholders including the Environmental Protection Agency, Sierra Club, and regional authorities like the Missouri River Basin Association.

Environmental impacts and restoration

River regulation altered sediment transport, seasonal flooding, and native habitat connectivity, contributing to declines in species such as Pallid sturgeon and loss of cottonwood recruitment studied by U.S. Geological Survey and universities including University of Missouri. Restoration initiatives by The Nature Conservancy, U.S. Fish and Wildlife Service, and state agencies in Nebraska Game and Parks Commission and Missouri Department of Conservation focus on reconnecting floodplain wetlands, managed flow experiments coordinated with the U.S. Army Corps of Engineers, and invasive species control targeting Saltcedar and nonnative carp, often informed by federal laws like the Clean Water Act.

Recreation and conservation areas

Significant protected and recreational areas within the floodplain include National Wildlife Refuges such as DeSoto National Wildlife Refuge, Big Lake National Wildlife Refuge, and Loess Bluffs National Wildlife Refuge, state parks like Lewis and Clark State Park (Iowa), and national historic sites tied to the Lewis and Clark Expedition and Fort Peck region. Riverfronts in St. Louis Riverfront, Kansas City Riverfront, and trails such as the Lewis and Clark National Historic Trail and local greenways provide boating, fishing, hiking, birdwatching, and cultural tourism supported by conservation NGOs like Missouri River Relief and academic programs at University of Nebraska Omaha.

Category:Missouri River