FLOOD04472

• County: Statewide
• Community: Nemaha County Nebraska
• Stream Name: Missouri River Miles 532.4-528.9
• Basin: Statewide
• Title: Langdon Bend Habitat Restoration/Preservation Project Volume 1
• Date: 6/1/1995
• Prepared For: US Army Corps of Engineers
• Prepared By: Greenhorne & O'Mara, Inc.
• Floodplain - Doc Type: Project

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Cottonwood and black willow are considered pioneer species and will not tolerate shaded
conditions. Their seeds which are dispersed by wind and water germinate best on moist mineral
soils, The seeds are viable for less than two weeks. Both will also produce stump sprouts.
Cottonwood is generally shortlived with growth peaking at 45 years, Trees over 70 years rapidly
deteriorate, but may reach a maximum age of 200 years.

The natural maintenance of riparian ecosystems requires frequent disturbances such as
those caused by a highly variable flow regime. Dam construction on the Missouri River has
resulted in slower growth for most of the tree species along the river and a low seedling
recruitment of cottonwood and willow. The long-term effect has been a decrease in biodiversity
within the riparian zone. Reduced peak flows cause less erosion which in turn can reduce
recruitment of native riparian trees. Pioneer cottonwood-willow associations will be replaced by
successional species of ash, elm, and maple since cottonwood and willow do not reproduce
successfully in forest conditions. In the Missouri River, high flows create the geomorphic
enviromnent for the establishment of riparian vegetation (Johnson, 1993). Channel meandering
is necessary to perpetuate extensive forests on the floodplain. However, woodland expansion and
channel narrowing may adversely affect migratory birds that use wide, active channels. A low
meandering rate will also result in the decline of pioneer and successional tree species, and will
provide less habitat for cavity-nesting birds and certain mammals,

Riparian vegetation performs numerous functions within the ecosystem, including: shading
streams and rivers, thereby reducing thermal stress on organisms; controlling streambank erosion
and sediment patterns; and contributing coarse woody debris for instream fish habitat. The woody
debris creates snag habitat which provides protection for invertebrates. The diversity of
invertebrates is greater on snags than the shifting sandbars in a main channel or the muddy
depositional areas of backwaters.

(2) Cropland. The majority of the site, approximately 537. I acres (74
percent), is in cropland at this time. Row crops of com and soybeans are the predominant
agricultural products. The Grable and Haynie soils which occur on the site are highly suitable
for row crops, especially com. With adequate drainage, the Onawa soils are also suited to row
crops, The Sarpy soils are best suited for pasture and yields of row crops are seldom satisfactory,

(3) Wetlands. Approximately 15.3 acres (2 percent) of the site consists of
wetlands. They include emergent, scrub/shrub, and forested wetlands as well as open water and
stream channels. The open water areas recede and essentially dry up in the summer, therefore,
no permanent hydraulic connection to the Missouri River exists. Emergent vegetation associated
with the wetlands includes smartweed and water cress. Woody vegetation associated with the
wetlands include sandbar and black willow and buttonbush (a list of common and scientific names
is included in Appendix A).

Wetlands provide significant ecosystem functions and values. Open water areas provide
habitat for resident and migratory waterfowl as well as aquatic organisms. In addition to

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