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USGS2007

Proceedings of the U.S. Geological Survey 2004 Mercury Workshop - Mercury research and its relation to Department of the Interior resource management

Introduction As part of the Department of the Interior (DOI) program Science on the DOI Landscape Initiative, the U.S. Geological Survey (USGS), Eastern Region, held a workshop during August 17–18, 2004, in Reston, VA, on mercury in the environment as it relates to DOI resource management. DOI bureaus manage millions of acres of land and offshore resources subject to mercury deposition and to the effects of mercury on ecosystems and human health. The goals of the workshop were to (1) summarize information on mercury sources and cycling on DOI lands in the eastern United States, (2) learn the perspectives of the DOI bureaus regarding mercury on DOI lands, (3) provide information to DOI land managers about monitoring mercury and minimizing mercury accumulation in wildlife and humans, and (4) consider future directions for mercury monitoring and research on DOI lands. The workshop focused on mercury research as it relates to DOI resource-management issues primarily in the eastern part of the United States (east of the Mississippi River). Topics included the influence of ecosystem setting on mercury biogeochemical transformation, land- and air-management practices as they affect mercury in the environment, mercury source issues, and effects of mercury on humans and wildlife. Mercury research topics were addressed by 24 invited oral presentations and 30 contributed posters. The perspectives of the DOI bureaus and land managers were addressed through a panel of scientists from the DOI resource-management bureaus and a Chippewa Indian Tribe of Minnesota. Discussion at the conclusion of the workshop was directed toward goals and long-term strategies for mercury research that will benefit DOI resource management. The panel, presentations, and discussions were videotaped and are available at the following URL, along with the slides presented: http://www.usgs.gov/mercury/2004workshop/ Abstracts from the presentations and posters are included in this report, together with summaries of each presentation session. The abstracts in this volume that were written by U.S. Geological Survey authors were reviewed and approved for publication by the Survey. Abstracts submitted by researchers from academia and from state and other federal agencies are published as part of these proceedings, but do not necessarily reflect the Survey’s policies and views. The use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Open-File Report↗

USGS1980

Analyses of water and dredged material from selected southern Louisiana waterways and selected areas in the Gulf of Mexico, 1976-78

The U.S. Geological Survey was requested by the U.S. Army Corps of Engineers to provide water-quality data to evaluate the potential environmental effects of (1) dredging activities in selected navigable waterways of southern Louisiana and (2) the disposal of dredged material at selected areas in the Gulf of Mexico. Areas studied from September 1976 to May 1978 included five ocean disposal sites in the Gulf of Mexico, in addition to the following waterways: Baptiste, Collette Bayou, Mississippi River at Head of Passes and Southwest Pass, Mississippi River at Tiger Pass, Bayou Black, Intracoastal Waterway (Port Allen to Morgan City), and Calcasieu River and Ship Channel. Samples were analyzed for selected chemical, physical, and biological constituents. (USGS)

Open-File Report↗

USGS2024

Defining the hafnium isotopic signature of the Appalachian orogen through analysis of detrital zircons from modern fluvial sediments

Fluvial sediments are the product of erosion, weathering, and transport of bedrock within a well-defined catchment area, and their constituent grains may therefore record valuable information about the lithological and geochemical properties of geologic units within the upstream drainage. Analysis of U-Pb ages and Lu/Hf isotopic values in detrital zircon grains from major rivers in the eastern USA characterizes these parameters within broad areas of the Appalachian orogen. In this study, five modern fluvial sediment samples, collected across ~1500 km and representing 216,000 km2 of total catchment area, reveal that the relative proportions of Mesoproterozoic to Paleozoic U-Pb crystallization ages vary widely across the former Laurentian margin. However, εHft values in the same samples are largely consistent regardless of their geographic location. Mesoproterozoic (Grenville orogen) zircons display a more limited range of εHft values (approximately 0 to +10 εHft units) compared to the more negative, more variable values (-15 to +10) found in grains from the Paleozoic orogenies. When compared to other published modern detrital samples from the Gulf Coastal Plain, Appalachian samples show more similarity to each other and to the Pleistocene of Florida than to those from the Mississippi River mouth, likely because the latter also sources sediments from the Cordillera of western North America. More negative εHft values in Paleozoic zircons may be genetically related to older Mesoproterozoic grains, as they are compatible with the continued isotopic evolution of Lu/Hf derived from the mantle between 1.2 and 2.0 Ga. Hafnium geochemistry in detrital grains may therefore have some utility in discerning sediment provenance between the Appalachians and other regions, and may also provide useful information regarding the nature of crustal generation through time.

Journal of Geology↗

USGS2020

Phylogeographic analysis of Mudpuppies (Necturus maculosus)

The geology of the Pleistocene, and particularly the Last Glacial Maximum approximately 26.5 ka, is a critical driver of species’ present-day distributions and levels of genetic diversity in northern regions. Using mitochondrial DNA sequence data, we tested several predictions relating to the postglacial recolonization of the northern United States and southern Canada by Mudpuppies (Necturus maculosus). Our analyses revealed a significant split between western and eastern lineages, with the divide corresponding to the location of the Mississippi River. Our data support the presence of one or more Mississippian glacial refugia, with subsequent expansion and diversification of a western cluster into the upper Midwest, and an eastern cluster into the eastern Great Lakes and New England. As predicted in cases of postglacial colonization, each of these clusters contains a single widespread and common haplotype, along with numerous low-frequency, closely related haplotypes. Given recent conservation concerns about amphibians in general, and Mudpuppies specifically, we discuss our results in light of species conservation. Knowledge of a species’ genetic diversity allows for informed management and facilitates decisions that preserve local adaptation and evolutionary potential.

Journal of Herpetology↗

USGS1967

Seismic measurements of explosions in the Tatum Salt Dome, Mississippi

Project Sterling provided for the detonation of a nuclear device in the cavity resulting from the Salmon nuclear explosion in the Tatum salt dome in southern Mississippi. It also provided for a high explosive (HE) comparison shot in a nearby drill hole. The purpose of the experiment was to gather information on the seismic decoupling of a nuclear explosion in a cavity by comparing seismic signals from a nuclear shot in the Salmon cavity with seismic signals recorded from Salmon and with seismic signals recorded from a muall (about 2 tons) HE shot in the salt dome. Surface seismic measurements were made by the U.S. Geological Survey, the U.S. Coast and Geodetic Survey, and the Air Force Technical Applications Center with coordination and overall direction by the Lawrence Radiation Laboratory. This report covers only the seismic measurements made by the U. S. Geological Survey. The first objective of this report is to describe the field recording procedures and the data obtained by the U. S. Geological Survey from these events. The second objective is to describe the spectral analyses which have been made on the data and the relative seismic amplitudes which have been determined from these analyses.

Mississippi↗

USGS1981

Geographic distribution and dispersal of normapolles genera in North America

Normapolles pollen have been found in North America in Cretaceous and Lower Tertiary rocks from the eastern Atlantic Seaboard, the Mississippi embayment region and from the states and provinces from western North America as far north as the District of Mackenzie, Northwest Territories. Previous postulates relating to the Normapolles floral province (western Europe-eastern North America) were re-examined in the light of new finds of Normapolles genera in rocks from west of the Cretaceous epeiric seaway which separated the Normapolles province from the western North American Aquilapollenites province. A study of published occurrences of Normapolles genera and U.S. Geological Survey Denver Laboratory Normapolles records revealed that of the approximately 60 Normapolles genera recognized from western Europe, only 26 of these have been recognized from eastern North America. These data suggest that Normapolles-producing plants originated in western Europe and migrated to eastern North America prior to the opening of the north Atlantic seaway. Ten of these 26 genera also have been found in rocks from west of the Cretaceous epeiric seaway, suggesting that these genera were the only ones able to cross this barrier. At least six genera having Normapolles characteristics occur in eastern North America but have not yet been recorded from Europe. Two additional genera with Normapolles characteristics have been reported only from the Aquilapollenites province of western North America. Several discrepancies in the record need resolution, such as the latitudinal restriction of Thomsonipollis and Nudopollis to areas south 40??N latitude, the absence of records of Thomsonipollis east and north of central Georgia, and the absence of records of Kyandopollenites and Choanopollenites west of eastern Texas. These data show that the known boundaries of the Normapolles province are somewhat hazy and that firm conclusions regarding the geographic distribution and history of dispersal of Normapolles genera are premature. ?? 1981.

Review of Palaeobotany and Palynology↗

USGS1962

Correlation of the Carrizo Sand in Arkansas and adjacent states

The Carrizo Sand (Eocene), the basal unit of the Claiborne Group, can be recognized in the subsurface throughout much of southeastern Arkansas and is correlated with the Carrizo Sand of Louisiana and the Meridian Sand Member of the Tallahatta Formation of Mississippi. The term Carrizo Sand is appropriate for use in Arkansas , as the stratigraphic terminology most workers apply to the Claiborne Group in Arkansas conforms with the terminology of Louisiana. A surface exposure of the Carrizo Sand in Arkansas is lithologically identical with described exposures of the Carrizo in northwestern Louisiana.

Arkansas, Louisiana, Mississippi, Tennessee↗

USGS1995

Duration of mineralization and fluid-flow history of the Upper Mississippi Valley zinc-lead district

Studies of fluid inclusions in sphalerite and biomarkers from the Upper Mississippi Valley zinc district show homogenization temperatures to be primarily between 90 and 150 ° C, yet show relatively low levels of thermal maturity. We use numerical calculations to simulate fluid and heat flow through fracture-controlled ore zones and heat transfer to the adjacent rocks. Combining a best-fit path through fluid-inclusion data with measured thermal alteration of biomarkers, we calculated the time interval during which mineralizing fluids circulated through the Upper Mississippi Valley district to be on the order of 200 ka. Cambrian and Ordovician aquifers underlying the district, principally the St. Peter and Mt. Simon Sandstones, were the source of the mineralizing fluid. The duration of mineralization thus reflects the fluid-flow history of these regional aquifers.

Geology↗

USGS2010

Attributes for MRB_E2RF1 Catchments in Selected Major River Basins of the Conterminous United States: Contact Time, 2002

This tabular data set represents the average contact time, in units of days, compiled for every MRB_E2RF1 catchment of Major River Basins (MRBs, Crawford and others, 2006). Contact time, as described in Vitvar and others (2002), is defined as the baseflow residence time in the subsurface. The source data set was the U.S. Geological Survey's (USGS) 1-kilometer grid for the conterminous United States (D.M. Wolock, U.S. Geological Survey, written commun., 2008). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) RF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

Data Series↗

USGS2010

Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Hydrologic Landscape Regions

This tabular data set represents the area of Hydrologic Landscape Regions (HLR) compiled for every MRB_E2RF1 catchment of the Major River Basins (MRBs, Crawford and others, 2006). The source data set is a 100-meter version of Hydrologic Landscape Regions of the United States (Wolock, 2003). HLR groups watersheds on the basis of similarities in land-surface form, geologic texture, and climate characteristics. The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

Data Series↗

USGS2008

Occurrence of transformation products in the environment

Historically, most environmental occurrence research has focused on the parent compounds of organic contaminants. Research, however, has documented that the environmental transport of chemicals, such as pesticides and emerging contaminants, are substantially underestimated if transformation products are not considered. Although most examples described herein were drawn from research conducted by the U.S. Geological Survey, such results are generally reflective of those found in other parts of the world. Results from a study of 51 streams in the Midwestern United States found that transformation products were seven of the ten most frequently detected pesticide compounds in late spring runoff (after application of pre-emergent herbicides), and nine of the ten most frequently detected compounds in fall season runoff (during and after harvest). In fact, 70% of the total herbicide concentration in water from the Mississippi River Basin was from transformation products. Results from a study of 86 municipal wells in Iowa found the frequency of detection increased from 17%, when pesticide parent compounds were considered, to 53%, when both parents and transformation products were considered. Transformation products were 12 of the 15 most frequently detected compounds for this groundwater study. Although studies on transformation products of synthetic organic compounds other than pesticides are not as common, wastewater treatment plant discharges have repeatedly been shown to contribute such transformation products to streams. In addition, select detergent transformation products have been commonly found in solid waste in the 1000's mg/kg. These findings and many others document that transformation products must be considered to fully assess the potential environmental occurrence of chemical contaminants and their transport and fate in various compartments of the hydrologic system. ?? 2008 Springer-Verlag Berlin Heidelberg.

The Handbook of Environmental Chemistry series↗

USGS1951

Index of surface-water records, part 7, Lower Mississippi River basin, to September 30, 1950

The index lists the steam-flow and reservoir stations in the Lower Mississippi River Basin for which records have been or are to be published for periods prior to September 30, 1950. The stations are listed in downstream order. Tributary streams are indicated by indention. Station names are given in their most recently published forms. Parentheses around part of a station name indicate that the inclosed word or words were used in an earlier published name of the station or in a name under which records were published by some agency other than the Geological Survey. The drainage areas, in square miles, are the latest figures published or otherwise available at this time. Drainage areas that were obviously inconsistent with other drainage areas on the same stream have been omitted. Some drainage areas not published by the Geological Survey are listed with an appropriate footnote stating the published source of the figure of drainage area. Under "period of record" breaks of less than a 12-month period are not shown. A dash not followed immediately by a closing date shows that the station was in operation on September 30, 1950. The years given are calendar years. Periods of records published by agencies other than the Geological Survey are listed in parentheses only when they contain more detailed information or are for period.s not reported in publications of the Geological Survey. Records both of gage height and of discharge are listed for stream-flow stations, and records of gage height and of contents (or of change in contents) are listed for stations on reservoirs. Records of gage heights only and records consisting only of monthly figures either of stream flow or reservoir contents are designated by symbols and footnotes. For early years when daily discharges were not generally published by the Geological Survey, published daily gage heights and a published rating table were considered to be equivalent to daily discharges. An alphabetical index of streams, canals, and reservoirs is given on pages 14-16.

Circular↗

USGS2013

Statewide summary for Louisiana: Chapter E in Emergent wetlands status and trends in the northern Gulf of Mexico: 1950-2010

Throughout the past century, emergent wetlands have been declining across the Gulf of Mexico. Emergent wetland ecosystems provide a variety of resources, including plant and wildlife habitat, commercial and recreational economic activity, and natural barriers against storms. As emergent wetland losses increase, so does the need for information on the causes and effects of this loss, emergent wetland mapping, monitoring and restoration efforts, and education. The U.S. Geological Survey and the U.S. Environmental Protection Agency’s Gulf of Mexico Program are committed to restoring, enhancing, and protecting these important ecosystems. The purpose of this report is to provide scientists, managers, and citizens with valuable baseline information on the status and trends of emergent wetlands along the coast of the Gulf of Mexico. This study examines the emergent wetlands of eight individual estuarine areas within the northern Gulf of Mexico region, as well as presenting statewide summaries for Texas, Louisiana, Mississippi, Alabama, and Florida. Each estuarine area is detailed in vignettes that address current status and historical trends of estuarine and palustrine emergent wetlands, emergent wetlands mapping and monitoring, causes of status change, restoration and enhancement activities, background information for the study area, and the methodology employed to analyze and document the historical trends and current status of emergent wetlands. This chapter examines the estuaries of Louisiana.

Louisiana↗

USGS1972

Geohydrologic summary of the Pearl River basin, Mississippi and Louisiana

Fresh water in abundance is contained in large artesian reservoirs in sand and gravel deposits of Tertiary and Quaternary ages in the Pearl River basin, a watershed of 8,760 square miles. Shallow, water-table reservoirs occur in Quarternary deposits (Pleistocene and Holocene) that blanket most of the uplands in .the southern half of the basin and that are present in smaller upland areas and along streams elsewhere. The shallow reservoirs contribute substantially to dry-weather flow of the Strong River and Bogue Chitto and of Holiday, Lower Little, Silver, and Whitesand Creeks, among others. About 3 billion acre-feet of ground water is in storage in the fresh-water section, which extends from the surface to depths ranging from about sea level in the extreme northern part of the basin to more than 3,000 feet below sea level in the southern part of the basin. Variations in low flow for different parts of the river basin are closely related to geologic terrane and occurrence of ground water. The upland terrace belt that crosses the south-central part of the basin is underlain by permeable sand and gravel deposits and yields more than 0.20 cubic feet per second per square mile of drainage area to streamflow, whereas the northern part of the basin, underlain by clay, marl, and fine to medium sand, yields less than 0.05 cubic feet per second per square mile of drainage area (based on 7-day Q2 minimum flow computed from records). Overall, the potential surface-water supplies are large. Because water is available at shallow depths, most of the deeper aquifers have not been developed anywhere in the basin. At many places in the south, seven or more aquifers could be developed either by tapping one sand in each well or by screening two or more sands in a single well. Well fields each capable, of producing several million gallons of water a day are feasible nearly anywhere in the Pearl River basin. Water in nearly all the aquifers is of good to excellent quality and requires little or no treatment for most uses. The water is a soft, sodium bicarbonate type and therefore has a low to moderate dissolved-solids content. Mineral content increases generally downdip in an aquifer. Excessive iron, common in shallow aquifers, is objectionable for some water uses. Water from the streams, except in salty tidal reaches, is less mineralized than ground water; in 10 sites the median dissolved-solids content in streamflow was 50 milligrams per liter or less. Moderately intensive ground-water development has been made in the Bogalusa area, Louisiana; at the Mississippi Test Facility, Hancock County, Miss. ; and in the Jackson area, Mississippi. Wells with pumping rates of 500 to 1,000 gallons per minute each are common throughout the Pearl River basin, and some deep wells flow more than 3,000 gallons per minute in the coastal lowland areas. Probably 20 million gallons per day of artesian water flows uncontrolled from wells in the southern part of the basin. Ground-water levels, except in the higher altitudes, are within 60 feet of the surface, and flowing wells are common in the valleys and in the coastal Pine Meadows. Decline of water level is a problem in only a few small areas. Saline water as a resource is available for development from aquifers and streams near the coast and from aquifers at considerable depth in most of the Pearl River basin. Pollution is a problem in oil fields and in reaches of some streams below sewage and other waste-disposal points. The basin estuary contains water of variable quality but has potential for certain water-use developments that will require special planning and management.

Water Supply Paper↗

USGS2016

St. Louis area earthquake hazards mapping project; seismic and liquefaction hazard maps

We present probabilistic and deterministic seismic and liquefaction hazard maps for the densely populated St. Louis metropolitan area that account for the expected effects of surficial geology on earthquake ground shaking. Hazard calculations were based on a map grid of 0.005°, or about every 500 m, and are thus higher in resolution than any earlier studies. To estimate ground motions at the surface of the model (e.g., site amplification), we used a new detailed near‐surface shear‐wave velocity model in a 1D equivalent‐linear response analysis. When compared with the 2014 U.S. Geological Survey (USGS) National Seismic Hazard Model, which uses a uniform firm‐rock‐site condition, the new probabilistic seismic‐hazard estimates document much more variability. Hazard levels for upland sites (consisting of bedrock and weathered bedrock overlain by loess‐covered till and drift deposits), show up to twice the ground‐motion values for peak ground acceleration (PGA), and similar ground‐motion values for 1.0 s spectral acceleration (SA). Probabilistic ground‐motion levels for lowland alluvial floodplain sites (generally the 20–40‐m‐thick modern Mississippi and Missouri River floodplain deposits overlying bedrock) exhibit up to twice the ground‐motion levels for PGA, and up to three times the ground‐motion levels for 1.0 s SA. Liquefaction probability curves were developed from available standard penetration test data assuming typical lowland and upland water table levels. A simplified liquefaction hazard map was created from the 5%‐in‐50‐year probabilistic ground‐shaking model. The liquefaction hazard ranges from low (<40% of area expected to liquefy) in the uplands to severe (>60% of area expected to liquefy) in the lowlands. Because many transportation routes, power and gas transmission lines, and population centers exist in or on the highly susceptible lowland alluvium, these areas in the St. Louis region are at significant potential risk from seismically induced liquefaction and associated ground deformation

Alabama, Arkansas, Illinois, Indiana, Iowa, Kentuc↗

USGS1943

Notes on the early history of water-well drilling in the United States

The standard cable-tool drilling rig was invented and developed in drilling salt wells in the West Virginia-Ohio-Pennsylvania region during the twenty years following the successful completion of the first drilled well in 1808 by the Ruffnet brothers at the Great Buffalo Lick near Charleston, West Virginia. Some time previous to 1823, Levi Disbrow studied the drilling methods used in the western salt industry and came east to become the first professional water well driller in the states north of the Potomac River. Possibly the first artesian water well in the United States was constructed in 1820 in Charleston, South Carolina, by sinking an iron pipe through a clay bed. Auger boring for artesian water appears to have been first used in Charleston, South Carolina, in 1823; however, the first successful auger-bored well was not completed in that city until after 1825. The drilling methods and tools were copied from a description of a well bored in London, England. Between 1821 and 1833 auger boring of artesian wells began in the Black Belt of Alabama and possibly in Mississippi. The process of jetting wells, invented in 1884, became the chief method of sinking artesian wells in the Atlantic and Gulf Coastal Plain by the end of the century. The first successful artesian wells in Georgia and Florida were put down during the period 1880-1882. © 1943 Society of Economic Geologists, Inc.

Economic Geology↗

USGS2010

Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Physiographic Provinces

This tabular data set represents the area of each physiographic province (Fenneman and Johnson, 1946) in square meters, compiled for every MRB_E2RF1 catchment of selected Major River Basins (MRBs, Crawford and others, 2006). The source data are from Fenneman and Johnson's Physiographic Provinces of the United States, which is based on 8 major divisions, 25 provinces, and 86 sections representing distinctive areas having common topography, rock type and structure, and geologic and geomorphic history (Fenneman and Johnson, 1946).The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

Data Series↗

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↗