Deep loess deposits are characteristic of the bluffs along the Missouri River in Missouri and Iowa and are particularly vulnerable to erosion and transport. Row crop cultivation on loessal upland soils adjacent to the floodplain often supply high amounts of sediment and the relatively steep gradient streams quickly carry the sediment load to the flood-plain where suspended materials are deposited. Some of the highest soil loss amounts in the United States are associated with loess deposits. Sediment losses from loessal streams threaten the remaining flood-plain water bodies along the Missouri River.
Squaw Creek National Wildlife Refuge, located on the Missouri River floodplain
in Holt County, Missouri (fig. 1), was established in 1935 to provide habitat
to migratory birds and other wildlife. A 1964 development plan summary report
compared a 1964 bathymetric survey of the Refuge wetlands to a 1937 survey and
described changes in the wetlands as a result of sedimentation as “alarming”.
Sedimentation poses problems in the Refuge in several ways including how it affects
the water depth and the ability to control water depths; how it affects the type
and distribution of vegetation; and how it fills control ditches and culverts
in the wetland, thus requiring constant resources to be used in the maintenance
and clearing of waterways. The ability to control water depths in specific pools
is critical in the management of the Refuge. To maintain the greatest possible
diversity of wildlife in the Refuge, managers also want a diversity in vegetation.
An inability to maintain proper water depths results in colonization of undesirable
vegetation species or the dominance of fewer species that are more readily adaptable
to shallower conditions. The ability to control the vegetation is important
in establishing desired food types and cover, or in some cases, the ability
to create open water to attract some species of migratory waterfowl. The Refuge
also supports the largest of two Missouri populations of the Massasauga rattlesnake.
The Massasauga rattlesnake is listed as an endangered species by the State of
Missouri and is a candidate for federal listing by the U.S. Fish and Wildlife
Service. The primary reason it is found in Squaw Creek is the existence and
maintenance of extensive Prairie cordgrass areas in the wetlands.
1. Determine depth, volume, and volume change of selected managed wetland pools in the Squaw Creek National Wildlife Refuge near Mound City, Missouri (fig 2).
2. Determine rate of sediment deposition in the refuge from 1937-1964, 1964-2002, and 1937-2002
3. Determine bulk density and sediment mass in selected managed wetland pools in the Squaw Creek National Wildlife Refuge.
4. Determine relative contributions of sediment from Squaw Creek National Wildlife Refuge source streams.
The USGS will benefit from a better understanding of the rate and delivery mechanisms of suspended sediment to the diminishing Missouri River wetlands including Squaw Creek National Wildlife Refuge. The unique hydrologic and physical conditions provided by the small streams in deep loessal bluffs along the Missouri River floodplain in northwest Missouri offer the opportunity to study sedimentation processes in an area previously unstudied in the State.
The results of this study will provide the cooperator with wetland pool depth, capacity, sediment mass, and sediment delivery rates, which will aid in the management of the Refuge. The change in pool volume may provide an indication of the lifespan of the refuge under current (2002) deposition conditions.
Selected Squaw Creek will be surveyed using a Total Station, Global Positioning System, Echo Sounder Bathy 500, and HYPACK software to determine the current bottom-elevation contours and water-holding capacity of each pool. These data will provide a detailed topographic map of each water body bottom. The 1937 and 1964 maps from Squaw Creek will be scanned or digitized for comparison with the digital bottom-elevation data collected in this study. Historic sedimentation rates will be determined by comparing the newly-mapped bottom elevations of these pools to those mapped in 1964 and 1937. Bottom samples will collected and analyzed for bulk density to convert volumes to mass of sediment deposited. Sedimentation rates at Squaw Creek for the 27 years between 1937-64, the 37 years between 1964-2001, and the 64 years between 1937-2001will be compared. These rates can be used to estimate the useful life of the affected water bodies and to assess the need for remediation.
U.S. Fish and Wildlife Service
David C. Heimann
U.S. Geological Survey
401 NW Capital Drive
Lee's Summit, Missouri 64086
PHONE: (816) 554-3489
FAX: (816) 554-9273
E-MAIL: dheimann@usgs.gov
U.S. Department of the Interior, U.S. Geological Survey
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Updated: August 29, 2003
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