A geomorphic history based on topographic map evidence

The Elkhorn River-Shell Creek drainage divide area in Antelope, Madison, Boone, and Platte Counties was eroded by a massive southeast-oriented flood, which had a source northwest of the Elkhorn River-Shell Creek drainage divide area. The southeast-oriented flood flow was captured in southern Boone and Platte Counties by headward erosion of an east-oriented anastomosing channel complex, including the present day Shell Creek and Platte River valleys. A second flood water source west of the Elkhorn River-Shell Creek drainage divide area supplied significant east-oriented flood flow. The southeast-oriented Shell Creek valley and parallel Elkhorn River valley eroded headward along southeast-oriented flood flow routes. The Elkhorn River valley after eroding north and northwest eroded southwest, northwest, and west-northwest to behead southeast-oriented flood flow routes to actively eroding southeast-oriented valleys, including the Shell Creek valley. Reversals of flood flow on the north ends of the beheaded flood flow routes eroded in sequence from east to west north-oriented Elkhorn River tributary valleys. Those north-oriented tributary valleys eroded south to capture yet to be beheaded southeast-oriented flood flow to the newly eroded and deeper Elkhorn River valley.

• The purpose of this essay is to use topographic map interpretation methods to explore Elkhorn River-Shell Creek drainage divide area landform origins in Antelope, Madison, Boone, and Platte Counties, Nebraska, USA. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions and/or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays in a comment here.

• This essay is also exploring a new geomorphology paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and other  Missouri River drainage basin landform origins research project essays is a thick North American ice sheet, comparable in thickness to the Antarctic ice sheet, occupied the North American region usually recognized to have been glaciated, and through its weight and erosive actions created a deep North American “hole”. The southwestern rim of that deep “hole” is today preserved in the high Rocky Mountains. The ice sheet through its weight and deep erosion (and perhaps deposition along major south-oriented melt water flow routes) caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.

• If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain Elkhorn River-Shell Creek drainage divide area landform origins evidence in Antelope, Madison, Boone, and Platte Counties, Nebraska will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm. This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Elkhorn River-Shell Creek drainage divide area location map

Figure 1: Elkhorn River-Shell Creek drainage divide area location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a location map for the Elkhorn River-Shell Creek drainage divide area in Antelope, Madison, Boone, and Platte Counties, Nebraska. The Missouri River flows in a south-southeast direction in the figure 1 east half from the north edge to the south edge. East of the Missouri River is the state of Iowa. West of the Missouri River is the state of Nebraska. Omaha is Nebraska’s largest city. The Platte River flows in a northeast direction from the figure 1 southwest corner to near Columbus where it turns to flow east-northeast to North Bend. After flowing east from North Bend to Fremont the Platte River turns to flow south and then east to join the Missouri River south of Omaha. The Elkhorn River flows in a southeast direction from the figure 1 northwest corner to Ewing, Clearwater, Neligh, Oakdale and Tilden. At Tilden the Elkhorn River turns to flow east to Norfolk and then southeast to Stanton, From Stanton the Elkhorn River flows northeast to Pilger and then turns to flow southeast and south-southeast to eventually join the Platte River west of Omaha. Shell Creek originates south of Tilden and flows in a southeast direction to near Platte Center (near Columbus) and then turns to flow east and east-southeast to join the Platte River east of Schuyler. The Elkhorn River-Shell Creek drainage divide area illustrated and discussed here is generally located south of the Elkhorn River and north of Shell Creek. Two unnamed Elkhorn River tributaries shown in figure 1 are illustrated and discussed in this essay. The first is the east- and north-oriented tributary joining the Elkhorn River near Battle Creek (west of Norfolk). That unlabeled stream is Battle Creek. The second unlabeled stream is Union Creek, which flows northeast through Madison and joins the Elkhorn River near Stanton. The Elkhorn River-Platte River drainage area in Stanton, Cuming, Colfax, and Dodge Counties essay discusses the region immediately east of the region illustrated and discussed here. The Niobrara River-Elkhorn River drainage divide area essay discusses the region located immediately north of the Elkhorn River-Shell Creek drainage divide discussed here. These essays can be located under Elkhorn River on the sidebar category list.  Hundreds of Missouri River drainage basin landform origins research project essays published on this website and located under appropriate Missouri River tributary names on the sidebar category list have presented a strong case for massive southeast-oriented melt water floods flowing to and across the Elkhorn River valley. The Elkhorn River valley is interpreted to have eroded headward to capture the southeast-oriented flood water. Evidence presented below further supports this southeast-oriented flood origin  interpretation.

Elkhorn River-Shell Creek drainage divide area detailed location map

Figure 2: Elkhorn River-Shell Creek drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 2 is a somewhat more detailed location map for the Elkhorn River-Shell Creek drainage divide area. Antelope, Pierce, Wayne, Madison, Stanton, Cuming, Boone, Nance, Platte, and Colfax are Nebraska county names and the county boundaries are shown. The Platte River is the east-northeast and east oriented river located near the figure 2 south edge (east half). The Elkhorn River flows in southeast direction into and across Antelope County and then in an east-southeast direction across northern Madison County to Norfolk. In Stanton County the Elkhorn River first flows in a southeast direction and then turns near Stanton to flow in a northeast direction. Near Pilger the Elkhorn River turns again to flow in a southeast and south direction across Cuming County and then to the figure 2 east edge. Note how the northeast oriented Elkhorn River segment corresponds with the alignment of northeast oriented Union Creek, which joins the Elkhorn River near Stanton. Shell Creek originates in northeast Boone County and flows in a southeast direction across the southwest corner of Madison County and into Platte County. Near Platte Center (slightly northwest of Columbus) Shell Creek turns to flow in an east direction parallel to the Platte River valley and joins the Platte River east of Schuyler in Colfax County. Other Elkhorn River tributaries of interest in this essay include north-oriented Cedar Creek, which joins the Elkhorn River near Oakdale; east-northeast and north oriented Battle Creek, which joins the Elkhorn River near Battle Creek; and Union Creek. Also of interest are Taylor Creek, a northeast and southeast-oriented Union Creek tributary which joins northeast oriented Union Creek near Madison and Meridian Creek, a northeast- and north-oriented stream which joins Union Creek east of Madison near the Madison-Stanton County boundary. Loseke Creek is an east- and south-oriented Shell Creek tributary of interest located in the east half of Platte County. Also of interest is the Loup River, which flows northeast in Nance County and western Platte County before turning to join the Platte River near Columbus. Note the large number of southeast-oriented Loup River tributaries west of the southeast-oriented Shell Creek segment. Like Shell Creek, instead of flowing to the Platte River those southeast-oriented streams flow to the Loup River, which flows parallel to the Platte River for a considerable distance before joining the Platte River. This evidence is interpreted to have originated because an immense southeast-oriented flood flowed across the figure 2 map area to join an even more concentrated east-northeast oriented flood along the figure 2 south edge area. Parallel valleys in the Platte River region are interpreted to have originated as channels in an east-northeast and east oriented anastomosing channel complex. Flood flow from the west probably continued after Elkhorn River headward erosion beheaded flood flow routes from the northwest.

Cedar Creek-North Fork Shell Creek drainage divide area

Figure 3: Cedar Creek-North Fork Shell Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the Cedar Creek-North Fork Shell Creek drainage divide area south of Oakdale. The east-southeast oriented Elkhorn River is located in the figure 3 northeast corner area. Oakdale is the town located on the figure 3 north center edge. Elgin is the town in the figure 3 west center edge area and Raeville is the small town in the figure 3 southwest quadrant. Meadow Grove is the town located where the highway crosses the figure 3 east edge (northeast corner area) and Tilden is the town located between Oakdale and Meadow Grove. Cedar Creek is the north-northeast and north-oriented Elkhorn River tributary flowing to join the Elkhorn River just north of the figure 3 map area near Oakdale. East of north-oriented Cedar Creek are additional north-oriented Elkhorn River tributaries including St. Clair Creek, Ives Creek, Giles Creek, Dry Creek, and Buffalo Creek. The northeast, east, and southeast oriented stream in the figure 3 south center area (flowing to the figure 3 south edge near Closter) is the North Fork Shell Creek. South of the figure 3 map area Shell Creek flows in a southeast direction until it gets close to the Platte River, at which point Shell Creek turns and flows roughly parallel to the east-oriented Platte River. Note how the north-oriented Elkhorn River tributaries have southeast-oriented barbed tributaries and northwest-oriented tributaries. This northwest-southeast oriented tributary orientation is evidence the north-oriented Elkhorn River tributary valleys eroded headward (or south) across multiple southeast-oriented flood flow channels such as might be found in a southeast-oriented anastomosing channel complex. Southeast-oriented tributary valleys were eroded by southeast-oriented flood flow moving into the newly eroded north-oriented tributary valleys. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded flood flow channels. This interpretation requires that the north-oriented Elkhorn River tributary valleys were eroded in sequence as what was at that time a deep Elkhorn River valley eroded headward across the figure 3 map area. Headward erosion of the Elkhorn River valley beheaded southeast-oriented flood flow and flood waters flowed north to the newly eroded and much deeper Elkhorn River valley. These north-oriented flood flow routes then eroded the north-oriented tributary valleys headward (or south) to capture yet to be beheaded southeast-oriented flood flow (not yet beheaded by Elkhorn River valley headward erosion). Note how northwest-oriented Cedar Creek tributary valleys are linked by through valleys with the North Fork Shell Creek valley. Figure 4 below provides a more detailed map of that Cedar Creek-North Fork Shell Creek drainage divide area.

Detailed map of Cedar Creek-North Fork Shell Creek drainage divide area

Figure 4: Detailed map of Cedar Creek-North Fork Shell Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 provides a detailed topographic map of the Cedar Creek-North Fork Shell Creek drainage divide area seen in less detail in figure 3 above. The west-east oriented Antelope-Boone County boundary is located just south of the figure 4 center. Cedar Creek flows in a north-northeast direction in the figure 4 northwest quadrant. North and northwest oriented streams east of Cedar Creek are Cedar Creek tributaries. The North Fork Shell Creek flows northeast and east in the figure 4 southeast quadrant. East of the figure 4 map area the North Fork Shell Creek turns to flow in a southeast direction (see figure 3 and also figure 2 above) and eventually reaches the Platte River. Note how headwaters of north- and northwest-oriented Cedar Creek tributaries are linked by through valleys with the northeast and east oriented North Fork Shell Creek valley. For example, in the section 3 southeast corner there is a north-south oriented through valley linking a northwest-oriented Cedar Creek tributary valley with an east-oriented North Fork Shell Creek tributary valley. Continue east and northeast along the drainage divide and two more through valleys are located near the section 2-section 3 boundary. More through valleys can be found crossing the drainage divide in either direction from section 3. Typically the through valleys are shallow notches in the drainage divide, with the deepest being 30-40 feet deep and some being only 10 or 20 feet deep. The through valleys are evidence of drainage routes that existed prior to headward erosion of deeper figure 4 valleys. At the time through valleys were eroded large volumes of flood water were moving in a southeast direction into what was then the actively eroding Shell Creek valley network. Flood water at that time was moving to the east-oriented Platte River valley area further to the southeast. Headward erosion of the deep Elkhorn River valley then beheaded southeast-oriented anastomosing flood flow channels in sequence, from east to west. Flood waters on north ends of beheaded flood flow channels reversed flow direction to flow to the newly eroded and much deeper Elkhorn River valley and in doing so started to erode north-oriented Elkhorn River tributary valleys. Those north-oriented valleys then eroded south to capture yet to be beheaded (by Elkhorn River headward erosion) southeast-oriented flood flow routes further to the south. The Cedar Creek valley in the figure 4 map area was eroding south-southwest to capture such yet to be beheaded flood flow. Flood waters on the northwest ends of flood flow routes beheaded by Cedar Creek valley headward erosion also reversed flow direction to erode northwest-oriented Cedar Creek tributary valleys and to create the Cedar Creek-North Fork Shell Creek drainage divide.

Battle Creek-Union Creek drainage divide area

Figure 5: Battle Creek-Union Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 illustrates the Battle Creek-Union Creek drainage divide area in Madison County east of the figure 3 map area. Madison is the town located in the figure 5 southeast quadrant. Battle Creek is the east and north oriented stream in the figure 5 northwest quadrant. North of the figure 5 map area Battle Creek continues to flow north to an east oriented Elkhorn River segment near the town of Battle Creek. Union Creek flows north-northeast to Madison in the figure 5 southeast quadrant and then east-southeast to the figure 5 east edge. East of figure 5 Union Creek turns to flow in a northeast direction to join the Elkhorn River near Stanton. The southeast-oriented North Fork Union Creek can be seen in the figure 5 southwest corner. Figure 7 below shows the region south of the figure 5 map area and the southeast-oriented Union Creek headwaters. Upstream from the Union Creek confluence the Elkhorn River flows in a southeast direction. Downstream from the Union Creek confluence the Elkhorn River flows in a northeast direction. The Elkhorn River elbow of capture at Stanton was created when headward erosion of the northeast-oriented Union Creek valley captured a significant southeast-oriented flood flow route. Headward erosion of that southeast-oriented flood flow channel further upstream eroded west and eventually beheaded flood flow routes to the actively eroding Union Creek valley, and as a result became the longer or more important valley. Flood waters on the north ends of some those beheaded southeast-oriented flood flow routes reversed flow direction to erode the north-oriented Battle Creek valley west of the northeast-oriented Union Creek valley. Headward erosion of the north-oriented Battle Creek valley beheaded southeast-oriented flood flow routes to the actively eroding Union Creek valley. Southeast-oriented Taylor Creek and the North Fork Taylor Creek flow to east- and northeast-oriented Union Creek at Madison and provide evidence of southeast-oriented flood flow routes beheaded by Battle Creek headward erosion. Note the northwest-southeast oriented through valleys linking the Battle Creek valley with the southeast-oriented Taylor Creek and North Fork Taylor Creek valleys. Figure 6 below provides a more detailed map of the Battle Creek-Taylor Creek drainage divide area.

Detailed map of Battle Creek-Taylor Creek drainage divide area

Figure 6: Detailed map of Battle Creek-Taylor Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 provides a detailed map of the Battle Creek-Taylor Creek drainage divide area seen in less detail in figure 5 above. Battle Creek flows east from the figure 6 west center edge and then turns north and northwest to flow to the figure 6 north edge. Taylor Creek flows in a southeast direction to the figure 6 southeast corner. North Taylor Creek flows in a southeast direction in the figure 6 northeast quadrant to the figure 6 east edge. Probably one of the most obvious figure 6 landforms is the large northwest-southeast oriented through valley linking the north and northwest oriented Battle Creek valley with the southeast-oriented Taylor Creek valley. This through valley which extends across the figure 6 center area provides evidence that large volumes of southeast-oriented flood flow once moved from the present-day north oriented Battle Creek valley area to the southeast-oriented Taylor Creek valley, which drains to the east-and northeast-oriented Union Creek valley. The through valley is almost 100 feet deep and its width exceeds one half mile. This through valley was eroded when the northeast-oriented Union Creek valley eroded headward into the region southeast of figure 6 (see figure 5) and captured southeast-oriented flood flow on the Taylor Creek alignment. Apparently a major southeast-oriented valley eroded headward, which developed a major south and southeast oriented flood flow route. Headward erosion of the deep Elkhorn River valley to the north and west then beheaded the south and southeast oriented flood flow route to what was then the actively eroding Taylor Creek valley. Flood waters on the north end of that beheaded flood flow route reversed flow direction to flow north to the newly eroded and deeper Elkhorn River valley. The reversed flow captured the Battle Creek headwaters (upstream from the figure 6 map area) and beheaded flood flow moving in a southeast-direction in the present day southeast-oriented through valley. Flood waters on the northwest end of the through valley reversed flow direction to flow in a northwest direction to what was then the newly created north and northwest oriented Battle Creek valley. Figure 6 evidence suggests flood water initially flowed across a topographic surface at least as high as the highest figure 6 elevations today. In other words, flood waters eroded all figure 6 erosional landforms.

Shell Creek-Union Creek drainage divide area

Figure 7: Shell Creek-Union Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 illustrates the Shell Creek-Union Creek drainage divide area southwest of the figure 5 map area. The west to east oriented Madison-Platte County line is located just south of the town of Newman Grove, located near the figure 7 west edge (north half). Shell Creek flows in a southeast direction from Newman Grove to the figure 7 south center edge. Lindsay is the small town located next to Shell Creek and southeast from Newman Grove. The northeast-oriented stream in the figure 7 northeast quadrant is Union Creek. The North Fork Union Creek flows in a southeast direction from the figure 7 north edge to join Union Creek in the figure 7 northeast quadrant. The South Fork Union Creek originates in the figure 7 center area as a southeast-oriented stream and then turns to flow in a northeast direction to join southeast-oriented North Fork Union Creek in the figure 7 northeast quadrant. Note how the northeast-oriented South Fork Union Creek and Union Creek segments both have barbed southeast-oriented tributaries from the northwest and barbed northwest-oriented tributaries from the southeast. This northwest-southeast tributary orientation provides evidence the Union Creek valley eroded headward to capture multiple southeast-oriented flood flow routes. The southeast-oriented tributary valleys were eroded headward from the newly eroded Union Creek valley wall along captured southeast-oriented flood flow routes. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of beheaded southeast-oriented flood flow routes. Note also how tributaries to the southeast-oriented Shell Creek valley are generally southeast-oriented or have significant southeast-oriented segments. Had the Union Creek valley eroded further to the southwest it would have captured flood flow moving southeast in the Shell Creek channel. However, apparently the Shell Creek channel had been eroded deep enough that it was already deeper than the Union Creek valley at the time the Union Creek valley was eroding headward into the figure 7 map region. Note how the figure 7 southwest quadrant region south and west of the Shell Creek valley is also drained by southeast-oriented streams.

Meridian Creek-Loseke Creek drainage divide area

Figure 8: Meridian Creek-Loseke Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 illustrates the Meridian Creek-Loseke Creek drainage divide area southeast of the figure 7 map area. Most of the figure 8 map area is located in the Platte County northeast corner and the west to east oriented Platte County north boundary is located near the figure 8 north edge. The southeast Madison County corner can be seen in the figure 8 northwest corner. Also present are the southwest Stanton County corner and the northwest Colfax County corner. Humphrey is the town located near the figure 8 west center edge. Creston is the small town located near the figure 8 center and Leigh is the town located in Colfax County near the figure 8 east edge. Meridian Creek flows in a north-northwest direction from near Creston and then turns to flow north-northeast to the figure 8 north edge. North of figure 8 Meridian Creek flows north to join northeast-oriented Union Creek at a location east of Madison (just east of the figure 5 map area). Tracy Creek flows in an east and northeast direction from the figure 8 edge (north of Humphrey) to join Meridian Creek north of Creston. Loseke Creek flows east-northeast and south in the figure 8 south center area. South of figure 8 Loseke Creek flows to east-oriented Shell Creek, which at that location is flowing parallel to the Platte River (see figure 9). East-oriented drainage near Leigh flows to the south-southeast West Fork Maple Creek, which like Shell Creek flows to the north edge of the east-oriented Platte River valley and then turns to flow in an east direction parallel to the Platte River. Note in figure 8 how northeast-oriented Tracy Creek-Meridian Creek segments have northwest-oriented tributaries from the southeast and southeast-oriented tributaries from the northwest. Also note how the east-northeast oriented Loseke Creek segment has southeast-oriented tributaries. The northwest-southeast tributary orientation is again evidence the northeast-oriented valley segments eroded headward across multiple southeast-oriented flood flow routes. The southeast-oriented tributary valleys were eroded headward along southeast-oriented flood flow routes captured by the newly eroded northeast-oriented valleys. The northwest-oriented tributary valleys were eroded by reversals of flood flow on the northwest ends of the beheaded southeast-oriented flood flow routes. Note the north-south through valley located south of Creston linking the north-oriented Meridian Creek valley with the south-oriented Loseke Creek valley. More detailed topographic maps show other shallow through valleys linking the northwest-oriented Tracy-Meridian Creek tributaries with southeast-oriented Loseke Creek tributaries. These through valleys provide additional evidence of the southeast oriented flood flow channels that crossed the figure 8 map area. The Loseke Creek valley eroded headward into the region first and the Meridian Creek-Tracy Creek valley was next.

Loseke Creek-Shell Creek drainage divide area

Figure 9: Loseke Creek-Shell Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 9 illustrates the Loseke Creek-Shell Creek drainage divide area south of the figure 8 map area and includes overlap areas with figure 8. Loseke Creek flows east-northeast in the figure 9 northwest quadrant and turns to flow in a south-southeast oriented direction in the figure 9 center area. Shell Creek flows in an east direction near the figure 9 south edge. South of the figure 9 map area is the east-southeast oriented Loup River (located in the same valley-see figure 10). Schaad Creek is the east-northeast tributary joining south-southeast oriented Loseke Creek near the figure 9 center. Note how the east-northeast oriented Loseke Creek segment and northeast-oriented tributary to that segment have north and northwest oriented tributaries. Also note southeast-oriented headwaters and tributaries flowing to east-northeast Schaad Creek. More detailed topographic maps show shallow through valleys linking north- and northwest-oriented Loseke Creek tributary valleys with southeast-oriented Schaad Creek tributary valleys, although the valleys are only 10-20 feet deep. The upland surface in the figure 9 west center area appears to be a flood eroded erosion surface into which the Schaad Creek and Loseke Creek tributary valleys were eroded. Northwest-southeast oriented through valleys crossing the Schaad Creek-Shell Creek drainage divide are much easier to identify and provide evidence of the multiple southeast-oriented flood flow routes that moved flood water from the northwest into the figure 9 map region. The large east-oriented valley in which the east-oriented Shell Creek channel is located appears to have been eroded headward across the southeast-oriented flood flow routes. While figure 9 evidence is limited presence of this large east-oriented valley suggests a major east-oriented flood occurred at about the same time the southeast-oriented flood water was also flowing into the figure 9 map area. The east-oriented flood probably had a different source (or at least flow route) than the southeast-oriented flood. Both floods were large, with the southeast-oriented flood flowing across much if not all of Nebraska (see essays listed under Niobrara River on sidebar category list for evidence from northern Nebraska drainage divides). East-oriented flood flow was more concentrated than the southeast-oriented flood flow and was able to erode the deeper Platte River valley westward, probably as a series of anastomosing flood flow channels. Platte River headwaters are in the Colorado and Wyoming Rocky Mountain areas and essays for those regions demonstrate some flood water responsible for eroding the Platte River valley came from those areas.

Shell Creek-Loup River drainage divide area

Figure 10 illustrates the Shell Creek-Loup River drainage divide area south and west of the figure 9 map area and includes overlap areas with figure 9. Columbus is the city located in the figure 10 southeast quadrant. Platte Center is the town located in the figure 10 north center area. The east-northeast oriented Platte River is located in the figure 10 southeast corner and is joined by the east and east-southeast oriented Loup River near the figure 10 east edge. Shell Creek is the southeast-oriented stream flowing from the figure 10 north center edge to near Platte Center and then turning to flow in an east direction along the north edge of the broad Platte River valley. East of the figures 9 and 10 map areas Shell Creek continues to flow parallel to the Platte River for a considerable distance before turning to join the Platte east of Schuyler. From the Schuyler area other east-oriented streams parallel the Platte River all the way to the south-southeast oriented Elkhorn River valley.  Irrigation canals have somewhat confused the Platte River valley drainage pattern, however the size of the broad east-oriented valley can be seen. The valley extends south from the Platte River channel almost as far as it extends north. West and southwest of the figure 10 map area the Loup River flows roughly parallel to the Platte River, although like Shell Creek near the valley’s north edge. Shallow through valleys west of Lake Babcock suggest that at one time water flowed from the present day Loup River channel into the east-oriented Shell Creek channel. In other words, the Platte River valley appears to have been eroded by a several east-oriented anastomosing flood flow channels, the northernmost of which was being fed by southeast-oriented flood water, which had been concentrated in multiple southeast-oriented valleys. This southeast-oriented flood flow appears to have been joining an east-oriented flood, which was responsible for eroding the deep Platte River valley headward across eastern Nebraska. Evidence from south of the Platte River, which can be found under appropriate Missouri River tributary names on the sidebar category list, demonstrates headward erosion of the east-oriented Platte River beheaded southeast-oriented flood flow into that region. Volumes of east-oriented flood water were great enough to erode what is today a significantly deeper and large east-oriented Platte River valley.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.