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Research about St. Charles County, Missouri

Source-linked reports with geographic coverage including St. Charles County, Missouri.

5 recordsLinked to original sources
USGS2020

Flood-inundation maps for Dardenne Creek in St. Charles County, Missouri, 2019

Digital flood-inundation maps for a 9.9-mile reach of Dardenne Creek, St. Charles County, Missouri, were created by the U.S. Geological Survey (USGS), in cooperation with the Missouri Department of Transportation, St. Charles County, and the Cities of O’Fallon and St. Peters, Mo. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Program website at https://www.usgs.gov/​mission-​areas/​water-​resources/​science/​flood-​inundation-​mapping-​fim-​program , depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgages 05514860 Dardenne Creek at Old Town St. Peters, Mo., and 05587450 Mississippi River at Grafton, Illinois. Near-real-time stages at these streamgages may be obtained from the USGS National Water Information System at https://doi.org/​10.5066/​F7P55KJN or the National Weather Service Advanced Hydrologic Prediction Service at https://water.weather.gov/ ahps2/ hydrograph.php? wfo= lsx&gage= drcm7 and https://water.weather.gov/ ahps2/ hydrograph.php? wfo= lsx&gage= grfi2 , which also forecasts flood hydrographs at these sites (sites DRCM7 and GRFI2). Flood profiles were computed for the Dardenne Creek stream reach by means of a one-dimensional model for simulating water-surface profiles with steady-state flow computations. The model was calibrated by using the current stage-streamflow relation at the USGS streamgages 05514840 Dardenne Creek at O’Fallon, Mo., and 05514860 Dardenne Creek at Old Town St. Peters, Mo., and the documented high-water marks from the flood of December 2015. The hydraulic model was then used to compute 17 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum and ranging from 16 ft, or near bankfull, to 32 ft at the reference streamgage 05514860. Stages in the lower Dardenne Creek can be affected by backwater from the Mississippi River; therefore, several sets of water-surface profiles were developed representing the extent of varying levels of backwater as referenced to the USGS streamgage 05587450 on the Mississippi River at Grafton, Ill. The upper stage for each map library exceeds the stage corresponding to the estimated 0.2-percent annual exceedance probability flood (500-year recurrence interval flood) at the streamgage location. The simulated water-surface profiles were then combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.26-ft vertical accuracy and 0.71-ft horizontal resolution) to delineate the area flooded at each water level. The availability of these maps, along with real-time information regarding current stage from the USGS streamgage and forecasted high-flow stages from the National Weather Service, will provide emergency management personnel and residents with information that is critical for flood mitigation, preparedness and planning, flood-response activities such as evacuations and road closures, and postflood recovery efforts.

Missouri↗
USGS1996

Geohydrology of the Weldon Spring ordnance works, St. Charles County, Missouri

Bedrock units at the Weldon Spring ordnance works in St. Charles County, Missouri, dip to the northeast at about 60 feet per mile, as measured by the top of the Chouteau Group. The top of the bedrock forms a generally east-west trending ridge through the Weldon Spring training area and the Weldon Spring chemical plant. This surface contains a large, broad bedrock low centered about the unnamed tributary to Dardenne Creek that contains Burgermeister spring. The low has been interpreted to be a paleodrainage that existed before deposition of glacial drift. This feature consists of smaller, more elongate paleovalleys at and west of the chemical plant where more dense drillhole data provide better definition. The uppermost bedrock unit throughout most of the ordnance works is the BurlingtonKeokuk Limestone of Mississippian age. It is subdivided based on weathering characteristics into a lower, unweathered unit; an upper, weathered unit; and a strongly weathered subunit of the weathered unit. The unweathered unit is a light to medium gray, coarse to less commonly fine crystalline, thin to massive bedded, fossiliferous, cherty limestone. The unweathered unit can be silty or argillaceous, or can locally be dolostone or siltstone. The weathered unit is characterized by an increase in mostly horizontal fractures and partings, increased porosity, vugs, voids, breccia, and discoloration by iron oxides. A strongly weathered subunit of the weathered unit is identified in some monitoring wells where these features are particularly abundant or intense. The overburden units are, in ascending order: residuum, basal till, glacial till, including a glacial outwash subunit, the Ferrelview Formation, loess, alluvium, and fill. Some of the thickest overburden occurs in the northern part of the training area and north of the training area and may be caused by a larger thickness of glacial drift. The paleodrainage centered about the unnamed tributary to Dardenne Creek that contains Burgermeister spring appears to have been partially filled by glacial drift, and a surface-water divide now exists southeast of the tributary. The upper, more permeable part of the shallow aquifer consists of the residuum, basal till, glacial outwash (where there is no glacial till below it), and the weathered unit of the Burlington-Keokuk Limestone. The lower, less permeable part of the shallow aquifer consists of the unweathered unit of the Burlington-Keokuk Limestone and the Fern Glen Formation. Generally, the upper part of the shallow aquifer thins to the north, reflecting the thin to absent weathered unit north of the training area and chemical plant. A glacial drift confining unit consists of parts of the glacial till and the Ferrelview Formation. Ground water as recharge and discharge probably moves in fractures through this unit. It confines ground water where the potentiometric surface of the shallow aquifer is above its base. There are stream reaches where the streams have cut through the glacial drift confining unit to expose the underlying shallow aquifer. A potentiometric surface map of the shallow aquifer shows a large ground-water mound in the south-central part of the training area. This mound is part of a generally east-west trending ground-water ridge through the training area and the chemical plant that defines a ground-water divide. Precipitation that percolates downward through fractures in the glacial drift confining unit recharges the shallow aquifer. Where the glacial drift confining unit is not present, precipitation can be expected to recharge the shallow aquifer more readily. There is the potential for groundwater flow in permeable overburden units where the potentiometric surface is above the top of bedrock. Generally, the residuum and locally other overburden units of the shallow aquifer potentially become more important as mediums of ground-water flow north and downgradient of the ground-water ridge. This is probably limited where clay-rich zones in the residuum confine ground water below in the bedrock. Because the thickness of the weathered unit generally decreases to the north, it generally becomes a less important medium of ground-water flow downgradient to the north. Also to the north, the potentiometric surface of the shallow aquifer is above the base of the glacial drift confining unit over a large area, indicating that the aquifer is confined. Upward ground-water gradients measured in monitoring well pairs, Burgermeister and other springs, the gaining unnamed tributary to Dardenne Creek upstream of Burgermeister spring, and Dardenne Creek indicate ground-water discharge in the northern part of the ordnance works.

Missouri↗