Geology topics

Research about Fort Morgan, Colorado

Source-linked reports with geographic coverage including Fort Morgan, Colorado.

3 recordsLinked to original sources

USGS2026

Reconstructing the Quaternary depositional history using geologic mapping and three-dimensional modeling of the subsurface near Fort Morgan, northeastern Colorado

Centered on Fort Morgan, Colorado, this study is intended to build from previous work by adding a three-dimensional (3D) view of the subsurface to better understand the depositional history of Quaternary deposits. A 1:100,000 scale geologic map was made by combining previous geologic maps, regional soil maps, and recent field investigations. In addition to the geologic mapping, drill hole lithologic data from water wells and oil and gas exploration were compiled and lithologic units simplified to best represent the stratigraphy of the Quaternary deposits. From these subsurface data, a 3D subsurface model was constructed, trimmed at the surface by a digital elevation model, and a bedrock surface foundation gridded from drill hole data was added. The surface of the 3D model was then compared visually to the surficial geologic map. Cross sections were constructed from the 3D model and compared to site-specific drilling that was done as part of this project. Finally, the model was examined in detail to reconstruct the depositional history of the subsurface alluvial and eolian units. Alluvial and fluvial drainage basins exposed in the subsurface have a greater areal extent than the present-day narrow drainages. Older eolian sand in the subsurface tends to be interbedded with loess indicating coeval deposition. Holocene sand, both eroded from bedrock exposed at the surface north of the study area and reworked from the South Platte River, buries most of the interbedded older sand and loess.

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USGS2018

Flood-inundation maps for the South Platte River at Fort Morgan, Colorado, 2018

In 2017, the U.S. Geological Survey (USGS), in cooperation with the Colorado Water Conservation Board (CWCB), studied floods in the historic record to produce a library of flood-inundation maps for the South Platte River at Fort Morgan, Colorado. Digital flood-inundation maps for a 4.5-mile (7.2-kilometers) reach of the South Platte River at Fort Morgan from Morgan County Road 16 to Morgan County Road 20.5, were created. The flood-inundation maps depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the U.S. Geological Survey streamgage on the South Platte River at Fort Morgan (streamgage number 06759500). Water-surface profiles were computed for the stream reach by means of a one-dimensional, step-backwater model. The September 15, 2013, and May 20, 2017, floods were used to calibrate the model, and the June 15, 2015, and May 29, 2017, floods were used to independently validate the model. Nine pressure transducers were deployed to record the stage at nine different locations along the reach and to document the floods of May 20 and 29, 2017, at the South Platte River at Fort Morgan streamgage. The hydraulic model was then used to compute 16 water-surface profiles for flood stages at 1-foot (ft; 0.3-meter [m]) intervals referenced to the streamgage datum and ranging from 12 ft (3.66 m) or below bankfull to 27 ft (8.23 m), which is 1 ft (0.3 m) greater than the highest recorded water level (25.73 ft [7.84 m] on September 15, 2013) at the South Platte River at Fort Morgan streamgage during its period of record; the 2013 flood exceeds the major flood stage of 21.5 ft (6.55 m) by more than 4 ft (1.2 m), as defined by the National Weather Service. 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 0.37-ft [0.11-m] vertical accuracy and 3.28-ft [1.00-m] horizontal resolution) to delineate the area flooded for stages ranging from 12 to 27 ft (3.66 to 8.23 m). These flood-inundation maps, in conjunction with the real-time stage data from the USGS streamgage on the South Platte River at Fort Morgan, are intended to help guide the general public in taking individual safety precautions and provide emergency management personnel with a tool to efficiently manage emergency flood operations and post flood recovery efforts.

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USGS1984

Streamflow gain-and-loss and suspended-sediment characteristics of the South Platte River and three irrigation canals near Fort Morgan, Colorado

A 2-year study during 1982-83 was made to document the streamflow gain-and-loss and suspended sediment characteristics of the South Platte River, Fort Morgan Canal, Upper Platte and Beaver Canal, and the Lower Platte and Beaver Canal near Fort Morgan, Colorado, prior to possible construction of the proposed Narrows Reservoir. Six streamflow gain-and-loss investigations, conducted in 1982 along a 25.8 mi reach of the South Platte River, indicate an average downstream gain in discharge of 150 cu ft/sec during the irrigation season. The Fort Morgan Canal and the Lower Platte and Beaver Canal had decreasing discharges in the downstream direction. The Upper Platte and Beaver Canal had a slight increased in discharge at the second measurement site and decreases in the third and fourth measurement sites. Irrigation practices and some loss to the groundwater system account for the general decrease in discharge. Suspended sediment data were collected at the streamflow-gaging station 06758500 South Platte River near Weldona and on the three irrigation canals: Fort Morgan Canal, Upper Platte and Beaver Canal, and Lower Platte and Beaver Canal. The data indicate that relations exist between the suspended sediment concentrations at the South Platte River station and the suspended sediment concentrations at the most upstream measurement site on each canal. Relations between suspended sediment discharge and water discharge were developed at all canal measurement sites. For all the canals, suspended sediment discharge decreased in a downstream direction. Slight increases in suspended sediment occurred at the second measurement site on the Upper Platte and Beaver Canal and at the third measurement site on the Lower Platte and Beaver Canal. Laboratory analyses indicate that 75% of the suspended sediment is silt and clay size (particles finer than 0.062 mm).

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