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Research about District of Columbia, Maryland, Virginia

Source-linked reports with geographic coverage including District of Columbia, Maryland, Virginia.

6 recordsLinked to original sources
USGS2006

Geologic map of the national parks in the National Capital region, Washington, D.C., Virginia, Maryland, and West Virginia

More than 51,000 acres within the National Capital Region (NCR) are administered by the National Park Service (NPS). These parks consist of parkways, trails, statues, monuments, memorials, historic sites, scenic areas, theatres, parks for performing arts, and Civil War battlefields. Although largely established for historical and cultural resources, each park is situated on a landscape that is influenced by bedrock and surficial geology of the central Appalachian mid-Atlantic region. Geologic mapping and field studies conducted for over 130 years are summarized here to provide the earliest history of the parklands. The age, type, names, and the interpreted origin of the rocks, as well as the processes active in the formation of surficial deposits and the landscape are discussed. These data are intended for educational and interpretative programs for visitors as well as the management of natural resources.

District of Columbia, Maryland, Virginia↗
USGS1987

A flow-simulation model of the tidal Potomac River

A one-dimensional model capable of simulating flow in a network of interconnected channels has been applied to the tidal Potomac River including its major tributaries and embayments between Washington, D.C., and Indian Head, Md. The model can be used to compute water-surface elevations and flow discharges at any of 66 predetermined locations or at any alternative river cross sections definable within the network of channels. In addition, the model can be used to provide tidal-interchange flow volumes and to evaluate tidal excursions and the flushing properties of the riverine system. Comparisons of model-computed results with measured watersurface elevations and discharges demonstrate the validity and accuracy of the model. Tidal-cycle flow volumes computed by the calibrated model have been verified to be within an accuracy of ? 10 percent. Quantitative characteristics of the hydrodynamics of the tidal river are identified and discussed. The comprehensive flow data provided by the model can be used to better understand the geochemical, biological, and other processes affecting the river's water quality.

District of Columbia, Maryland, Virginia↗
USGS1985

Controls on phosphorus mobility in the Potomac River near the Blue Plains wastewater treatment plant

The Blue Plains wastewater treatment plant is the largest point source of phosphorus in the Potomac River basin, discharging an average of 2 metric tons of phosphorus into the river each day in 1980. An intensive study of the water and sediments in the vicinity of the treatment plant was conducted in 1979-80 in order to characterize the major factors controlling the mobility of effluent-derived phosphorus in the area. The transport of phosphorus near the treatment plant was found to be affected by the circulation regime, by inorganic adsorption reactions with sediments, and by metabolic uptake and release by phytoplankton. The effect of river discharge on the convective transport of phosphorus near the outfall is significantly reduced by a mid-river shoal area, which confines the flow path of the effluent to an embayment on the eastern side of the river for a distance of 4 kilometers below the outfall. This embayment appears to serve as a sediment trap, where protection from bottom scour during high-flow events has permitted fine-grained sediments to accumulate. Measurements of mean residence time indicate that the effluent leaves the embayment area 21? days after being discharged from the outfall. Measurements of the linear decay constant for the removal of dissolved phosphorus from the water column reveal a diurnal cycle corresponding to the metabolic utilization of phosphorus by phytoplankton. This cyclic removal is superimposed on a constant and noncyclic adsorption of phosphorus by inorganic phases. Forty-eight hour average values of the linear decay constant for dissolved phosphorus in the area range from 0.4 to 1.1 per day. Analyses of bottom sediments indicate that approximately 13 percent of the phosphorus discharged between September 1977 and August 1980 has been retained in the embayment. The primary inorganic phase responsible for phosphorus adsorption is amorphous iron (ferric oxy-hydroxides); amorphous aluminum and clay minerals appear to play secondary roles. The accumulation of sorbed phosphorus in the embayment has been promoted by the deposition of fine-grained sediments enriched in ferric oxy-hydroxides. Conversely, the absence of ferric oxy-hydroxides in coarse-grained sediments near the outfall has facilitated the precipitation of the ferrous phosphate mineral vivianite.

District of Columbia, Maryland, Virginia↗