A geomorphic history based on topographic map evidence

The Beaver Creek-Cedar River drainage divide area between the South Fork Elkhorn River and the Loup River was eroded by a massive southeast-oriented flood. Evidence for the southeast-oriented flood flow is found in the present day orientation of southeast-oriented Beaver Creek and Cedar River valleys and many of their tributary and other valleys, but also in shallow northwest-southeast oriented through valleys eroded across present day drainage divides. The northwest end of the Beaver Creek-Cedar River drainage divide area is located in the eastern Nebraska sand hills region and may be a location where flood waters from further to the north and west were temporarily ponded and deposited significant sediment. Southeast-oriented flood waters flowed to the northeast-oriented Loup River-Platte River valley, which had eroded headward across the southeast-oriented flood flow and which captured the southeast-oriented flood flow and diverted the flood waters northeast and east to what was then probably a newly eroded Missouri River valley.

Preface:

• The purpose of this essay is to use topographic map interpretation methods to explore Beaver Creek-Cedar River drainage divide area landform origins between South Fork Elkhorn River and Loup River, 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 Beaver Creek-Cedar River drainage divide area landform origins evidence between South Fork Elkhorn River and Loup River, 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.

Beaver Creek-Cedar River drainage divide area location map

Figure 1: Beaver Creek-Cedar River 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 Beaver Creek-Cedar River drainage divide area between the South Fork Elkhorn River and the Loup River and shows a region central and eastern Nebraska. The Platte River flows in a northeast direction from Grand Island near the figure 1 south center edge to Columbus and Schuyler near the figure 1 east edge. The South Loup  River flows in a southeast direction in the figure 1 southwest corner area to Pleasanton and then turns to flow northeast and joins the southeast-oriented Middle Loup River near Boelus and the southeast-oriented North Loup River downstream from St Paul. The Loup River then continues in a northeast direction to join southeast-oriented Cedar River (unlabeled on figure 1) near Fullerton and southeast-oriented Beaver Creek near Genoa before joining the Platte River near Columbus. The Elkhorn River flows in a southeast direction from O’Neil in the figure 1 north center area to Ewing, Clearwater, Neligh, Oakdale, Tilden, Norfolk, Stanton, and Pilger before reaching the figure 1 east edge. The South Fork Elkhorn River is the unlabeled east-flowing stream flowing from Amelia (located in the figure 1 north center area) to join the southeast-oriented Elkhorn River near Ewing. The unlabeled northeast oriented stream joining the Elkhorn River near Clearwater is Clearwater Creek. South of the Clearwater Creek headwaters are headwaters for southeast-oriented Beaver Creek, which flows through Albion and St Edward before joining the Loup River near Genoa. South of the South Fork Elkhorn River headwaters are headwaters for southeast-oriented Cedar River, which flows through Ericson, Spalding, Primrose, Cedar Rapids, and Belgrade before joining the Loup River near Fullerton. Maps and discussions in this essay focus on the region south of the South Fork Elkhorn River, north of the Loup River, southwest of Beaver Creek, and northeast of the Cedar River. The Elkhorn River-Loup River drainage divide area between Shell and Beaver Creeks essay and the Elkhorn River-Shell Creek drainage divide area in Antelope, Madison, Boone, and Platte Counties essay address regions located immediately east of the Beaver Creek-Cedar River region discussed and illustrated here. The Niobrara River-Elkhorn River drainage divide area essay addresses the region north of the region described here. Those 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 have presented substantial evidence that an immense southeast-oriented flood flowed across Nebraska and was captured by headward erosion the northeast and east oriented Platte River valley. The predominance of southeast-oriented drainage routes in figure 1 north of the northeast-oriented Loup River valley segment provides additional evidence supporting this interpretation. The southeast-oriented flood flow was captured by headward erosion of the northeast-oriented Platte River and Loup River valleys and was subsequently beheaded by Elkhorn River valley headward erosion in the north.

Beaver Creek-Cedar River drainage divide area detailed location map

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

Figure 2 is a more detailed location map for the Beaver Creek-Cedar River drainage divide area between the South Fork Elkhorn River and the Loup River. Antelope, Pierce, Garfield, Wheeler, Madison, Valley, Greeley, Boone, Nance, and Platte are Nebraska county names and county boundaries are shown. Holt County is west of Antelope County. The northeast oriented Platte River can just barely be seen in the figure 2 southeast corner. The northeast and east oriented Loup River is located just north and west of the Platte River and joins the Platte River near Columbus along the figure 2 east edge. The South Fork Elkhorn River originates near Amelia in Holt County and flows east to join the Elkhorn River near Ewing (near the Holt County-Antelope border, also note the east and northeast oriented South Fork Elkhorn River tributary that originates near Swan Lake). The Elkhorn River flows in a southeast direction from Ewing across Antelope and northern Madison Counties to Norfolk located near the figure 2 east edge. Note northeast oriented Clearwater Creek, which originates along the Holt-Wheeler County boundary and which flows east and northeast to join the Elkhorn River near Clearwater and northeast oriented Cache Creek, between Clearwater Creek and the South Fork Elkhorn River. Beaver Creek originates in northeast Wheeler County and flows in a southeast direction across Boone County to join the Loup River in northeast Nance County. Cedar River headwaters are located in northern Garfield County and the Cedar River flows in a southeast direction across the Wheeler County southwest corner, Greeley County northeast corner, and Boone County southwest corner before joining the northeast oriented Loup River in Nance County near the figure 2 south edge. Plum Creek is a south-southeast oriented Loup River tributary located between Beaver Creek and Cedar River in Boone and Nance Counties. Beaver Creek tributaries important in the discussion below include Skeedee Creek (in Nance County) and Bogus Creek (in Boone County). Cedar River tributaries of importance in the discussion below include Silver Valley Creek in Boone County and Mud Creek, which is located near the Wheeler-Boone-Greeley County corner. The drainage history interpretation here is an immense southeast-oriented flood flowed across the figure 2 map region. Flood waters were first captured by headward erosion of what was then a deep northeast and east oriented Platte River-Loup River valley, which diverted flood waters eastward to what was then a newly eroded south-oriented Missouri River valley (east of the figures 1 and 2 map areas). Subsequently headward erosion of Elkhorn River valley and its northeast- and east-oriented tributary valleys, including the Clearwater Creek, Cache Creek, and South Fork Elkhorn River valleys, beheaded southeast-oriented flood flow to what were then actively eroding southeast-oriented Beaver Creek and Cedar River valleys.

Beaver Creek-Cedar River drainage divide area at the Loup River

Figure 3: Beaver Creek-Cedar River drainage divide area at the Loup River.United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the south end of the Beaver Creek-Cedar River drainage divide area where southeast oriented Beaver Creek and Cedar River flow to the northeast oriented Loup River. The Loup River flows in a northeast direction from the figure 3 southwest corner area to the figure 3 east center area. The Loup River is flowing along the north edge of the broad northeast and east oriented Platte River valley, with the Platte River channel located south of the figure 3 map area. Fullerton is the town located in the figure 3 southwest corner and is located between the northeast-oriented Loup River and the southeast oriented Cedar River. Genoa is the town located near the figure 3 east edge and is located on southeast oriented Beaver Creek, just upstream from where Beaver Creek joins the Loup River. Skeedee Creek is the southeast-oriented tributary, which joins Beaver Creek near Genoa. Merchiston is the small town (or place-name) located northeast from Fullerton near where a southeast-oriented stream flows to the Loup River. That southeast-oriented stream is Plum Creek. East of Plum Creek in the figure 3 center area is southeast- and south-oriented Council Creek, which also flows directly to the Loup River. Note the presence of a relatively smooth, although gently southeast-sloping, upland erosion surface located between the various southeast-oriented Loup River tributaries. This erosion surface is a flood eroded erosion surface that existed prior to headward erosion of the present day deep southeast-oriented Loup River tributary valleys. At the time the erosion surface was formed the Loup River-Platte River valley did not exist and flood waters continued south into regions further south. Headward erosion of what was then the deep east and northeast oriented Platte River-Loup River valley captured the southeast-oriented flood flow and diverted the flood waters northeast and east to what was then a newly eroded south-southeast oriented Missouri River valley. The deep southeast-oriented Loup River tributary valleys then eroded headward along the southeast-oriented flood flow routes and developed tributary valley systems to capture the southeast-oriented flood flow. Headward erosion of the valleys was sequential with the Beaver Creek valley eroding headward first (in the figure 3 map area) and the Cedar River valley eroding headward last (in the figure 3 map area). Tributary valleys to these southeast-oriented Loup River valleys were also eroded in sequence, with southern tributary valleys being eroded first and northern valleys last. Figure 4 below provides a detailed map of Skeedee Creek-Council Creek drainage divide area.

Skeedee Creek-Council Creek drainage divide area

Figure 4: Skeedee Creek-Council Creek drainage divide area.United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 4 provides a detailed map of the Skeedee Creek-Council Creek drainage divide area seen in less detail in figure 3 above. Skeedee Creek flows in a southeast direction from the figure 4 north center edge across section 2 and section 1 to flow east along the section 6 and 7 border to the figure 4 east edge. Council Creek originates in section 4 in the figure 4 northwest corner and flows in a southeast direction across sections 10 and 14 to reach the figure 4 south center edge. The Skeedee Creek and Council Creek valleys appear to have been eroded into what was a relatively flat erosion surface, which may have had a slight south or southeast oriented slope. In section 11 in the figure 4 center area there is evidence of a shallow south-oriented through valley linking a north-oriented Skeedee Creek tributary valley with the southeast-oriented Council Creek valley. Another shallow through valley can be seen in section 4 (figure 4 northwest corner) and links the Council Creek headwaters with a north-oriented Skeedee Creek tributary. Still another shallow through valley can be identified in section 12. While these through valleys are subtle, they do provide evidence that multiple channels of south-oriented water once flowed across the Skeedee Creek-Council Creek drainage divide. Much more obvious through valleys can be seen crossing drainage divides between southeast-oriented Skeedee Creek tributaries in sections 3, 2, 1 6, and 7. These deeper through valleys provide evidence that water flowed south across those drainage divides prior to headward erosion of the more northern deeper southeast-oriented valleys. The figure 4 drainage history can be reconstructed by assuming the deep valleys eroded headward into the region to capture south-southeast oriented flood flow moving across the entire figure 4 map area. Headward erosion of he Council Creek valley occurred prior to headward erosion of the Skeedee Creek valley, with southern valleys in each valley network eroding headward prior to headward erosion of the more northern valleys, which beheaded south-southeast-oriented flood flow to the newly eroded southern valleys.

Plum Creek-Bogus Creek drainage divide area

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

Figure 5 illustrates the Plum Creek-Bogus Creek drainage divide area north and west of the figure 3 map area.  The Cedar River flows in a south-southeast direction in the figure 5 southwest quadrant from Cedar Rapids along the west edge to the south edge. Beaver Creek flows in a south-southeast direction in the figure 5 northeast quadrant from north of Boone to St Edward (the town located along the figure 5 east edge). Plum Creek flows in a south-southeast direction across the figure 5 center area and flows from the figure 5 north edge to the figure 5 south edge. Bogus Creek is located between Plum Creek and Beaver Creek and flows in a southeast direction to join Beaver Creek just east of the figure 5 east edge. Bogus Creek is typical of Beaver Creek and Cedar River tributaries and the Bogus Creek valley eroded west and northwest of the south-southeast oriented Beaver Creek valley to capture south-southeast oriented flood flow moving west of the actively eroding Beaver Creek valley. Bogus Creek tributaries eroded in sequence with the northeast-oriented Bogus Creek tributaries eroding headward first. As the Bogus Creek valley eroded headward the southeast-oriented Bogus Creek tributary valleys eroded headward in sequence, with southern valleys eroding headward first. Headward erosion of the Bogus Creek valley network ceased when headward erosion of the Beaver Creek valley permitted headward erosion of east and southeast oriented tributary valleys north of the figure 5 map area, which beheaded flood flow routes to the actively eroding Bogus Creek valley system. Figure 6 below provides a detailed map of drainage divides between Bogus Creek tributaries to illustrate the presence of through valleys, along which south-southeast oriented flood flow once moved. Note in figure 5 how Plum Creek has a narrow drainage basin and how Plum Creek tributaries on both sides are short. Compared to many drainage basins the Beaver Creek and Cedar River drainage basins are also narrow. These multiple narrow south-southeast oriented drainage basins suggests the valleys eroded headward along a significant south-southeast oriented flood flow channels and did not capture much flood water from adjacent flood flow routes.

Through valleys crossing Bogus Creek tributary drainage divides

Figure 6: Through valleys crossing Bogus Creek tributary drainage divides.United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 6 provides a detailed map of Bogus Creek tributary drainage divides seen in less detail in figure 5 above. Bogus Creek flows in a southeast direction across the figure 6 northeast quadrant. Highway 56 is the west to east oriented highway crossing figure 6 near the north edge. The highway roughly parallels a northeast and east oriented Bogus Creek tributary valley. An east-southeast oriented Bogus Creek tributary valley is located in the figure 6 south half and begins in section 11 near the figure 6 west edge and drains in an east-southeast direction in sections 12 and 7 and in section 8 joins a northeast-oriented Bogus Creek tributary valley near the  section 8 south edge. A close look at the drainage divide between these two east-oriented Bogus Creek tributaries reveals the presence of multiple through valleys. For example, starting in the west, near the section 2 southeast corner, is a through valley and then in section 1 there are at least three more through valleys. In the south of section 6 there are at least three more shallow through valleys and another shallow through valley can be located in the section 8 northwest corner. While certainly not deep or particularly obvious features these shallow through valleys provide evidence of multiple south-oriented flood flow channels, such as might be found in a flood formed anastomosing channel complex. The valleys probably were eroded by southeast-oriented flood flow moving to the southern east-oriented Bogus Creek tributary valley prior to headward erosion of the northern east-oriented Bogus Creek tributary. Probably both valleys eroded west at approximately the same time, although the southern valley eroded west slightly ahead of the northern valley. Headward erosion of the northern valley beheaded flood flow routes to the newly eroded southern valley, although because headward erosion of the northern valley beheaded the south-oriented flood flow routes one channel at a time, and because the channels were anastomosing (interconnected), flood waters on the north ends of the beheaded channels not only reversed flow direction to flow north into the northern valley, but also were able to capture yet to be beheaded flood flow from flood flow channels further to the west. Such captures of yet to be beheaded flood flow provided the water necessary to erode the north-oriented valleys to the northeast east-oriented Bogus Creek tributary valley.

Silver Valley Creek-Plum Creek drainage divide area

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

Figure 7 illustrates the Cedar River-Silver Creek-Plum Creek-Beaver Creek drainage divide areas north and west of the figure 5 map area. Primrose is the small town in the figure 7 southwest corner and the Cedar River can be just barely seen flowing in a southeast direction near Primrose. Albion is the larger town near the figure 7 east center edge and Beaver Creek is the southeast oriented flowing through Albion. Plum Creek flows in a southeast direction from the figure 7 northwest quadrant across the figure 7 center area to the figure 7 south edge. Silver Creek originates in the figure 7 west center area and flows in a south-southeast and south direction into the figure 7 southwest quadrant and joins Cedar River south of the figure 7 map area. Again drainage basins of the major southeast and south-southeast oriented streams are long and narrow, which suggests the valleys eroded headward at approximately the same time. Tributaries are short and often parallel to the major streams. West of Albion Beaver Creek has northeast oriented tributaries with north-northwest oriented headwaters (and also southeast oriented headwaters). The northeast oriented tributary valleys eroded southwest from what was then a newly eroded Beaver Creek valley to capture southeast oriented flood flow moving west of the still actively eroding Beaver Creek valley. These tributary valleys were eroded in sequence with the southern valleys eroding southwest first and then more northern valleys eroding southwest in progression as the actively eroding Beaver Creek valley head eroded further to the northwest. The north-northwest oriented tributary headwaters valleys were eroded by reversals of southeast oriented flood flow on the north ends of beheaded flood flow routes. Note how in the figure 7 northwest quadrant a southeast, northeast, southeast and northeast oriented Plum Creek tributary has beheaded the southeast-oriented flood flow route that were moving flood waters to what had been the actively eroding Silver Creek valley network. The first (western) southeast-oriented valley segment of that Plum Creek tributary valley probably is the captured headwaters of what had been the Silver Creek valley. The second southeast-oriented valley segment is probably the captured headwaters of a Plum Creek tributary valley located just to the southeast. Figure 8 below provides a detailed map of the Plum Creek-Beaver drainage divide area northwest of Albion and illustrates through valleys crossing the drainage divides.

Detailed map of Beaver Creek-Plum Creek drainage divide area

Figure 8: Detailed map of Beaver Creek-Plum Creek drainage divide area.United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 is a detailed map of the Plum Creek-Beaver Creek drainage divide area northwest of Albion seen in less detail in figure 7 above. Plum Creek flows in southeast direction across the figure 8 southwest corner. Beaver Creek meanders in a southeast direction in the figure 8 northeast corner area. The purpose of figure 8 is to illustrate north-south through valleys linking the various east oriented Beaver Creek tributary valleys and also the Plum Creek valley. Beginning in section 32 in the figure 8 northwest corner area there are headwaters of an east and northeast oriented stream, which north of the figure 8 map area turns to flow southeast into section 34 and join the east and northeast oriented stream which joins Beaver Creek in section 35 (just north of figure 8 map area). Note in the figure 8 northwest corner area how there are shallow north-south through valleys linking the headwaters of that east-oriented Beaver Creek tributary with headwaters of south-oriented Plum Creek tributary valleys and also in the section 5 northeast corner with headwaters of a northeast-oriented tributary valley to that same east-oriented Beaver Creek tributary. Note in section 4 how that northeast-oriented Beaver Creek tributary valley has north-oriented tributary valleys and how in section 9 just to the south the headwaters of those north-oriented tributary valleys are linked by through valleys to a south-oriented Plum Creek tributary valley and to a southeast and northeast oriented Beaver Creek tributary valley. Also note in section 3 a north-oriented tributary valley to the northeast-oriented Beaver Creek tributary valley in sections 34 and 35. Then follow the north-oriented valley headward into section 10 and there is a through valley linking the north-oriented valley with a southeast-oriented Beaver Creek tributary valley. Close inspection of the figure 8 drainage divides reveals additional through valleys linking the present day drainage routes. The through valleys are evidence of multiple southeast-oriented flood flow routes that existed just prior to headward erosion of the present day deep valleys. Flood flow in the through valleys was initially moving to the southern valley and was subsequently beheaded and reversed by headward erosion of the northern deep valley. Reversal of flood flow often captured yet to be beheaded flood flow from adjacent yet to be beheaded flood flow routes, and with the aid of the captured flood waters eroded the deep north-oriented valleys seen today.

Cedar River valley northwest from Spalding

Figure 9 illustrates the Cedar River valley northwest from Spalding. Spalding is the town located in the figure 9 southeast quadrant. The Cedar River flows in an east and southeast direction from the figure 9 west edge to Spalding and to the figure 9 south edge. Mud Creek is the south-southeast oriented Cedar River tributary located along the figure 9 east edge. Clear Creek is south-southeast oriented Cedar River tributary flowing from the figure 9 northwest quadrant to and from Pibel Lake in the figure 9 west center area. Note the figure 9 region northwest of Spalding where sections 36, 31, 1, and 6 are marked. Figure 9a below provides a more detailed map of that region. Note how in that region there is a northwest and south oriented Cedar River tributary with a large south and southwest oriented valley draining to it. Also note how the southwest and northwest oriented valley segments are linked by through valleys with other south-oriented Cedar River tributaries, which have eroded what appears to be a badland type topography into the region just to the south. What has happened here is headward erosion of the south-oriented Cedar River tributary valley along the figure 9a west edge beheaded southeast-oriented flood flow moving along the present day northwest oriented valley segment in sections 25 and 31. That southeast-oriented flood flow was eroding the multiple south-oriented valleys in sections 6, 5, and 4 headward until the southeast-oriented flood flow was beheaded. The southwest oriented valley in sections 29 and 31 had probably originated as a southwest-oriented tributary to the southeast-oriented flood flow route. Flood waters on the beheaded southeast-oriented flood flow route reversed flow direction to flow northwest to the newly eroded and deeper south-oriented Cedar River tributary valley. The reversed flow captured the southwest-oriented tributary valley flow and enough flood water subsequently flowed in this newly developed south, southwest, northwest, and south oriented Cedar River tributary valley to erode the large valley to its present depth and shape. Note also in figure 9 above how the north end of this south, northwest, and south oriented Cedar River tributary valley appears to have beheaded southeast-oriented flood flow routes to the south-southeast oriented Mud Creek headwaters. Much of the figure 9 west half appears to be covered with wind-blown sediments, which has obscured flood eroded channels and makes drainage history reconstructions from topographic maps difficult and sometimes impossible.

Figure 9a: Detailed map of drainage divide area northwest of Spalding.United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Beaver Creek-Cedar River drainage divide area northwest of Spalding

Figure 10: Beaver Creek-Cedar River drainage divide area northwest of Spalding.United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 uses reduced size maps to show the Beaver Creek-Cedar River drainage divide area northwest of Spalding. The figure 9 and 9a map areas are included in the figure 10 southeast quadrant area. Cedar Creek flows in southeast direction from the figure 10 northwest corner and joins southeast-oriented Dry Cedar Creek near Ericson. Downstream from Ericson the stream is named the Cedar River and the Cedar River flows in a southeast direction to Spalding located near the figure 10 southeast corner. Beaver Creek is the east-southeast and southeast oriented stream located in the figure 10 northeast quadrant. The figure 10 map area appears to be covered by sand dunes, which has obscured many drainage routes. Figure 10a below provides a more detailed map of the Cedar Creek-Dry Cedar Creek confluence area northwest of Ericson and illustrates evidence for the eolian deposits. This region is along the eastern margin of the Nebraska Sand Hills area. Wind blown materials in this region probably are derived from flood deposited sediments, which suggests there may have been significant ponding of flood waters in central and western Nebraska. Evidence presented earlier in this essay suggested flood waters from two different source areas (or at least which had flowed along two very different routes) converged in central Nebraska. The convergence of the southeast-oriented flood flow with the east-oriented flood flow may have been responsible for ponding of the flood waters and the deposition of large quantities of flood transported sediment. Evidence presented in this essay is not adequate to support this speculative hypothesis. Whatever the reason for ponding of flood waters and subsequent deposition of the sediments, wind activity at a later time has probably buried all but the most significant figure 10 drainage routes. Topographic maps do not permit easy drainage history reconstructions in such regions and for that reason we must rely on drainage histories from adjacent regions. Evidence from the region southeast of this figure 10 map area suggests large volumes of southeast-oriented flood water once flowed across this region. Figures 1 and 2 above illustrate that the South Fork Elkhorn River valley and the Elkhorn River valleys eroded headward across the region north of this figure 10 map area. Headward erosion of the Elkhorn River (and South Fork Elkhorn River) valley would have beheaded all southeast-oriented flood flow moving to what must have been the actively eroding Beaver Creek and Cedar River drainage basins.

Figure 10a: Cedar Creek-Dry Cedar Creek confluence near Ericson.United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

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.