A geomorphic history based on topographic map evidence

The Logan Creek-Missouri River drainage divide area in Dakota, Thurston, and Burt Counties is located in northeast Nebraska, USA. Logan Creek is a southeast and south oriented Elkhorn River tributary located west of the south-southeast Missouri River. Through valleys link north-oriented (barbed) Missouri River tributary valleys with the south oriented Logan Creek valley. North-oriented (barbed) Missouri River tributaries have southeast-oriented tributaries and headwaters, providing evidence of capture of southeast-oriented flood flow. Through valleys also cross drainage divides between north-oriented Missouri River tributary valleys and south and east oriented Missouri River tributary valleys. These through valleys are interpreted to have been eroded as south and south-southeast oriented channels in a what was a large-scale south-oriented anastomosing channel complex. The anastomosing channel complex was formed during an immense south-oriented flood, which was responsible for eroding the present day northeast Nebraska drainage system. Flood erosion of northeast Nebraska ended when the deep Missouri River valley eroded headward and beheaded all south- and southeast-oriented flood flow routes.

Preface:

• The purpose of this essay is to use topographic map interpretation methods to explore Logan Creek -Missouri River drainage divide area landform origins in Dakota, Thurston, and Burt 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 Logan Creek-Missouri River drainage divide area landform origins evidence in Dakota, Thurston, and Burt 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.

Logan Creek-Missouri River drainage divide area location map

Figure 1: Logan Creek-Missouri 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 Logan Creek-Missouri River drainage divide area in Dakota, Thurston, and Burt Counties, Nebraska. The south-southeast oriented Missouri River is located in the figure 1 center and east of the Missouri River is Iowa and west of the Missouri River is Nebraska. In the figure 1 north center edge area, northwest of Sioux City, Iowa, the southeast tip of South Dakota can be seen. Logan Creek is the unlabeled stream flowing southeast and south-southeast west of the Missouri River and flows through Laurel, Wakefield, Pender, Bancroft, Lyons, and Oakland before joining the Elkhorn River near Hooper. From Hooper the Elkhorn River flows south-southeast and south to join the Platte River near Elkhorn. From Elkhorn the Platte River flows south and then east to join the south-southeast oriented Missouri River near the figure 1 south edge. The Elkhorn River-Logan Creek drainage divide area in Wayne, Stanton, and Cuming Counties essay describes the region located west of the Logan Creek-Missouri River drainage divide area and the Bow Creek-Logan Creek drainage divide area essays describes the region located north of the Logan Creek-Missouri River drainage divide area. These essays can be found under Elkhorn River on the sidebar category list. Landforms in the Logan Creek-Missouri River drainage divide area are interpreted to have been eroded by an immense south or south-southeast oriented flood at the time the Missouri River valley eroded headward across the figure 1 map region. Flood waters were coming from a rapidly melting ice sheet, the southern margin of which at that time was located just north of the figure 1 map area. Essays found under James River on the sidebar category list describe how south-oriented melt water floods sliced a large south-oriented ice-walled and bedrock-floored valley into the ice sheet’s surface. Prior to Missouri River valley headward erosion flood waters moving south in that James River lowland valley would have flowed south into northeast Nebraska. Also, those south-oriented flood waters would have been joined by southeast-oriented melt water floods moving along the ice sheet’s southwest margin. These south- and southeast-oriented flood waters significantly lowered the northeast Nebraska topographic surface and enabled the deep Missouri River valley and its tributary valleys to erode headward into the region. The Platte River valley-Elkhorn River valley-Logan Creek valley eroded headward into the region as the Missouri River valley was eroding headward further to the east. North of the figure 1 map area the Missouri River valley eroded northwest and west and captured the south- and southeast-oriented flood water that had flowing to what had been the actively eroding Logan Creek valley. Since that time the Logan Creek-Missouri River drainage divide area landscape in Dakota, Thurston, and Burt Counties has not been significantly altered.

Logan Creek-Missouri River drainage divide area detailed location map

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

Figure 2 provides a slightly more detailed location map for the Logan Creek-Missouri River drainage divide area in Dakota, Thurston, and Burt Counties, Nebraska. The Missouri River is the south-southeast oriented river in the figure 2 center. Iowa is the state east of the Missouri River and Nebraska is the state west of the Missouri River. Dixon, Dakota, Wayne, Thurston, Stanton, Cuming, Burt and Colfax are Nebraska county names and county boundaries are shown. Woodbury, Monona, and Harrison are Iowa county names. The north half of the red shaded area in Thurston County is Winnebago Indian Reservation land. The red shaded area in southern Thurston County and northeast Cuming County is Omaha Indian Reservation land. The Elkhorn River flows east and northeast in Stanton County and southeast in Cuming County to reach the figure 2 south center edge. Logan Creek originates in the figure 2 northwest corner area and flows in a southeast direction across the Dixon County southwest corner, the Wayne County northeast corner, the Thurston County southwest corner, and the Cuming County northeast corner before flowing in a south direction through western Burt County and to join the southeast-oriented Elkhorn River near the figure 2 south center edge. Note the barbed Missouri River tributaries in the Dakota, Thurston, and Burt County area. For example, Omaha Creek flows north in Thurston County and into Dakota County to join the south-southeast oriented Missouri River. South Blackbird Creek originates as a southeast-oriented stream in northern Burt County, but then makes a U-turn to flow north into Thurston County and then to join the south-southeast-oriented Missouri River. An unnamed northeast-oriented stream joins the south-southeast oriented Missouri River at Decatur (located in northern Burt County). These barbed tributaries provide evidence that headward erosion of the deep Missouri River valley beheaded multiple south-oriented flood flow channels, such as might be found in a south or south-southeast oriented anastomosing channel complex. As each south-oriented channel was beheaded flood waters on the north end of the beheaded flood flow channel reversed flow direction to flow north to the newly eroded and much deeper south-southeast oriented Missouri River valley. Because the flood flow channels were anastomosing (or interconnected) and because headward erosion of the Missouri River valley beheaded the flood flow channels one channel at a time, reversed flow in the newly beheaded flow channels captured yet to be beheaded flood flow from channels further to the west. Note southeast-oriented Omaha Creek and South Blackbird Creek tributaries and headwaters for evidence of such captures.

Omaha Creek drainage basin

Figure 3: Omaha Creek drainage basin. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Omaha Creek drainage basin in northern Thurston County and southern Dakota County. The southeast-oriented Missouri River valley is located in the figure 3 northeast corner. Emerson is the town located in the figure 3 northwest quadrant. The Dakota-Thurston County border extends in an east-west direction through Emerson. Thurston is the town located in the figure 3 southwest quadrant. Logan Creek is the southeast-oriented stream seen in the figure 3 southwest corner. Middle Creek is the south-southeast and south-southwest oriented Logan Creek tributary flowing from the Emerson area to Thurston and then to Logan Creek. Homer is the town located on the edge of the Missouri River valley and near the figure 3 north edge in the figure 3 northeast quadrant. Winnebago is the town located in the figure 3 east center area and Walthill is the town located on the figure 3 south edge almost directly south from Winnebago. Omaha Creek is the southeast-oriented stream in the figure 3 center, which flows almost to Walthill and then makes a U-turn to flow almost directly north to Winnebago and Homer, where it enters the southeast-oriented Missouri River valley as a barbed tributary. Walthill is located in the valley of north-oriented South Omaha Creek, which flows to the north-oriented Omaha Creek valley segment. Cow Creek is the southeast-oriented stream in the figure 3 south center area. South of figure 3 Cow Creek flows to north-oriented South Omaha Creek as a barbed tributary. Note also southeast-oriented Morgan Creek and southeast-oriented Turtle Creek, which flow to the north-oriented Omaha Creek valley segment as barbed tributaries south and north of Winnebago respectively. What has happened here is prior to headward erosion of the deep Missouri River valley an immense south-oriented flood flowed across the figure 3 map area on a topographic surface at least as high, if not higher, than the highest present day figure 3 elevations. Headward erosion of the deep Logan Creek valley enabled south-oriented valleys to erode headward into the figure 3 map area to capture the south and southeast oriented flood flow and to divert the flood waters to the deep south-oriented Logan Creek valley. The first such valley eroded north along the present day Omaha Creek alignment and the southeast-oriented tributary valleys were initiated by southeast-oriented flood flow flowing into that south-oriented Omaha Creek valley. Headward erosion of the Middle Creek valley occurred next and beheaded some of the southeast-oriented flood flow routes to the newly eroded Omaha Creek valley. At about the same time the deep Missouri River valley eroded headward into the region and beheaded south-oriented flood flow routes to the south-oriented Omaha Creek valley. Flood waters on the north end of the Omaha Creek valley reversed flow direction to flow north to the much deeper Missouri River and created the north-oriented Omaha Creek drainage basin seen today. North Blackbird Creek is the south-southeast and south oriented stream along the figure 3 east edge (south half) and the Omaha Creek-North Blackbird Creek drainage divide area is illustrated in detail in figure 4 below.

Omaha Creek-North Blackbird Creek drainage divide area

Figure 4 provides a detailed topographic map of the Omaha Creek-North Blackbird drainage divide area near Winnebago seen in less detail in the figure 3. Omaha Creek is the north oriented stream flowing near the figure 4 west edge. North Blackbird Creek is the south-southeast oriented stream flowing to the figure 4 southeast corner area. Note the northwest oriented Omaha Creek tributaries in the Winnebago area. A close look at the figure 4 drainage divides reveals these northwest oriented tributary valleys are linked by through valleys with headwaters of southeast-oriented North Blackbird Creek tributaries (and with the North Blackbird Creek headwaters valley). For example, in section 16 northwest oriented headwaters of a northwest and southwest oriented Omaha Creek tributary are linked by a 40-50 feet deep though valley with the North Blackbird Creek valley. In the southeast corner of section a 40-50 foot deep through valley links headwaters of a northwest-oriented Omaha Creek tributary with headwaters of a southeast-oriented North Blackbird tributary. Also in the south center of section 20 a north and northwest oriented Omaha Creek tributary is linked by three 20-40 foot deep through valleys with a southwest-oriented Omaha Creek tributary. Many additional similar through valleys can be seen crossing the figure 4 drainage divides. These through valleys provide evidence of the south-oriented anastomosing channel complex that was being eroded into the figure 4 topographic surface prior to headward erosion of the present day trunk stream valleys. The North Blackbird Creek valley first eroded headward into the figure 4 map region to capture the southeast-oriented flood flow and to divert the water south to what was then the actively eroding Missouri River valley head. Headward erosion of the south-oriented Omaha Creek valley occurred next and beheaded southeast-oriented flood flow routes to the actively eroding North Blackbird Creek valley and tributary valleys. Flood waters on the northwest ends of the beheaded flood flow routes reversed flow direction to flow in a northwest direction to the newly eroded Omaha Creek valley. By reversing flow direction the flood waters eroded the northwest-oriented Omaha Creek tributary valleys and created the Omaha Creek-North Blackbird Creek drainage divide. At approximately the same the deep Missouri River valley eroded north and northwest and beheaded south-oriented flood flow in the Omaha Creek valley. Flood waters on the north end of the Omaha Creek valley reversed flow direction to flow north to the newly eroded and much deeper Missouri River valley.

South Omaha Creek-Logan Creek drainage divide area

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

Figure 5 illustrates the South Omaha Creek-Logan Creek drainage divide area south of the figure 3 map area. The south-southeast oriented Missouri River is located in the figure 5 northeast corner. Southeast-oriented Logan Creek is located in the figure 5 southwest quadrant. Note the Logan Creek channel has been altered by human activity, although segments of the original channel are shown. Big Slough is the southeast oriented stream flowing from the figure 5 northwest quadrant to join Logan Creek. Walthill is located along the figure 5 north center edge. The north-oriented stream flowing to Walthill is South Omaha Creek. Cow Creek flows southeast to the figure 5 north center area and joins north-oriented South Omaha Creek as a barbed tributary. Rosallie is the town located on the drainage divide between the north-oriented South Omaha Creek headwaters and the southeast oriented Big Slough valley (the Rosallie area is shown in greater detail in figure 6 below).  Note how Rosallie is located in a north-south oriented through valley. The through valley provides evidence water once flowed south in the present day north-oriented South Omaha Creek-Omaha Creek valley. Macy is the town located in the figure 5 northeast quadrant. The east-oriented stream at Macy is North Blackbird Creek which flows in a south-southeast direction just west of Macy before turning to flow east to the Missouri River valley. Downstream from Macy at the Missouri River valley edge the north-northeast oriented stream joining North Blackbird Creek is South Blackbird Creek. Like Omaha Creek South Blackbird Creek has south-oriented headwaters and the South Blackbird Creek headwaters are located in the figure 5 south center area immediately east of the north-south highway. Figure 7 below illustrates the region where South Blackbird Creek makes a U-turn and turns from flowing south to flowing north. Note how an east-northeast oriented North Blackbird Creek tributary valley has eroded west to behead south-oriented flood flow to the south-oriented South Blackbird Creek valley. The figure 5 drainage pattern and landforms can best be explained in the context of an immense south- and southeast-oriented flood moving across the entire figure 5 map area prior to headward erosion of any trunk stream valleys. Headward erosion of the Logan Creek valley first captured the flood flow and diverted the flood waters to the newly eroded Elkhorn River and Platte River valleys (and Missouri River valley further downstream). Headward erosion of the deep Missouri River valley next beheaded the south-oriented flood flow routes in sequence. South-southwest oriented flood flow on what was then the South Blackbird Creek flood flow route to the newly eroded Logan Creek valley was reversed to flow north-northeast and to create the present day South Blackbird Creek drainage basin. Headward erosion of the deep Missouri River next beheaded south-oriented flood flow on the Omaha Creek-South Omaha Creek flood flow route. Reversed flood flow on that beheaded flood flow route created the present day Omaha Creek-South Omaha Creek drainage basin and the South Omaha Creek-Big Slough drainage divide.

Detailed map of South Omaha Creek-Big Slough drainage divide area

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

Figure 6 provides a detailed map of the South Omaha Creek-Big Slough drainage divide area near Rosallie seen in less detail in figure 5 above. Big Slough is the south-southeast oriented stream flowing from the figure 6 northwest corner to the figure 6 south edge (south of Rosallie). South Omaha Creek originates in the figure 6 northeast quadrant region and flows west-northwest before turning to flow north to the figure 6 north center edge. Note how a south-oriented Big Slough tributary originates just north of Rosallie and flows south through Rosallie to join Big Slough just south of the figure 6 south edge. Also note the large north-south through valley in section 10 at Rosallie linking the north-oriented South Omaha Creek valley with the south-southeast oriented Big Slough valley. Section 10 is one mile wide and the through valley, which fills most of section 10, is 70 to 80 feet deep. The valley size provides evidence as to the amount of south-oriented flood water that flowed south from the Omaha Creek drainage basin. Further east in the section 14 northeast quadrant and the section 13 north half are additional through valleys linking north-oriented South Omaha Creek tributaries with headwaters of a southwest-oriented Big Slough tributary. The through valleys provide evidence of multiple south-oriented flood flow routes, which once moved water south across the location where the west-northwest oriented South Omaha Creek valley is now located. Reversal of south-oriented flood flow in the South Omaha Creek drainage basin was responsible for capturing the south-oriented flood flow and eroding the present day west-northwest oriented South Omaha Creek valley. The fact the west-northwest oriented South Omaha Creek valley could be eroded as much as it was provides some evidence as to the volumes of flood water moving across the present day Logan Creek-Missouri River drainage divide region. Reversal of flood flow in the South Omaha Creek valley did not begin until after headward erosion of the deep Missouri River valley had beheaded all south-oriented flood flow routes to the figure 6 map area. Yet there was still enough flood water south of the newly eroded and deep Missouri River valley to be able to erode the west-northwest oriented South Omaha Creek valley and also to significantly deepen the north-oriented South Omaha-Omaha Creek valley.

South Blackbird Creek U-turn northeast of Lyons, Nebraska

Figure 7: South Blackbird Creek U-turn northeast of Lyons, Nebraska. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 7 illustrates the South Blackbird Creek U-turn northeast of Lyons, Nebraska and is located south and slightly east of the figure 5 map area and includes overlap areas with figure 5. Rosallie is located just west of the figure 7 northwest corner. Lyons is the town located in the figure 7 southwest corner. Logan Creek is the south-oriented stream flowing along the figure 7 west edge (south half) and Big Slough can be seen flowing along the figure 7 west edge (north half). The Missouri River valley is located along the figure 7 east edge and the Missouri River channel can be seen in the figure 7 northeast quadrant. Decatur, Nebraska is the town located in the figure 7 east center area adjacent to the Missouri River. Elm Creek is the north and northeast oriented stream joining the Missouri River as a barbed tributary at Decatur. East of Elm Creek is north-oriented  Lone Tree Creek, which is also flowing to the south-southeast oriented Missouri River as a barbed tributary. South Blackbird Creek is located in the figure 7 center area and flows south-southeast before making a U-turn in the figure 7 center south area to flow north and then north-northeast to the figure 7 north edge (and then to the Missouri River valley as a barbed tributary (see figure 5 above). South-oriented drainage east of Lyons (and south of the South Blackbird Creek U-turn) are headwaters of south-oriented Bell Creek. South of the figure 7 map area Bell Creek continues to flow south between the south-oriented Logan Creek and Missouri River valleys and eventually joins the southeast-oriented Elkhorn River (downstream from where Logan Creek joins the Elkhorn River). Figure 7 drainage patterns and other landforms are again best explained by deep erosion from an immense south-oriented flood which deeply eroded the entire figure 7 region. Flood waters originally moved south across the entire figure 7 map area on a topographic surface at least as high, if not higher, than the highest figure 7 elevations today. Flood waters probably began to erode anastomosing south-oriented flood flow channels headward from what was then the newly eroded southeast-oriented Elkhorn River valley segment located south of the figure 7 map area (see figure 9 below). Flood flow was probably greatest just east of the figure 7 map area and the deep Missouri River valley was able to erode north and north-northwest to behead in sequence the south-oriented flood flow channels. Flood waters on the north ends of the beheaded south-oriented flood flow channels reversed flow direction to flow north to the newly eroded and much deeper south-southeast oriented Missouri River valley in what are today barbed tributary valleys.

Detailed map of South Blackbird Creek-Wood Creek drainage divide area

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

Figure 8 provides a detailed map of the South Blackbird Creek-Wood Creek drainage divide area seen in less detail in the figure 7 northeast quadrant above. The south-southeast oriented Missouri River can be seen in the figure 8 northeast corner. South Blackbird Creek flows in a northeast and north direction from the figure 8 west center edge to the figure 8 north edge. North and northwest oriented drainage in the figure 8 north center area flows to north-oriented South Blackbird Creek. Note how South Blackbird Creek has multiple northwest-oriented tributaries. Wood Creek is the northeast and southeast oriented Missouri River tributary flowing from the figure 8 south center area to the figure 8 east edge (south half). Note the southeast-oriented tributaries to the northeast-oriented Wood Creek valley segment. Further, note how northwest-oriented South Blackbird Creek valleys are linked by through valleys with southeast-oriented Wood Creek tributary valleys. These through valleys appear to be shallow when compared to the depth of the opposing valley floors on either side, however they provide evidence water once flowed in multiple southeast-oriented channels across what is today the northeast-oriented South Blackbird Creek valley into what is today the northeast-oriented Wood Creek valley segment. Also note how the northwest-southeast oriented highway along the Missouri River-Wood Creek drainage divide crosses shallow through valleys eroded into that drainage divide. The shallow through valleys are located at the heads of south-oriented Wood Creek tributaries and provide evidence that headward erosion of the deep Missouri River valley beheaded multiple south-oriented flood flow channels to what must have been the newly eroded southeast-oriented Wood Creek valley. A close study of the figure 8 map area and similar maps for adjacent areas reveals numerous such through valleys notched into all major drainage divides. The through valleys provide evidence of a large-scale south-oriented anastomosing channel complex, which had been eroded into the figure 8 map region topographic surface prior to headward erosion of the present day trunk stream valleys. Flood waters initially flowed across the figure 8 map area on a topographic surface at least as high as the highest present day elevations, if not higher.

Logan Creek-Missouri River drainage divide area northwest of Hooper

Figure 9: Logan Creek-Missouri River drainage divide area northwest of Hooper. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Logan Creek-Missouri River drainage divide area northwest of Hooper, Nebraska and south of the figure 7 map area. The south oriented Missouri River valley is located along the figure 9 east edge. The south oriented Logan Creek valley is located near the figure 9 west edge. The Elkhorn River flows in a southeast direction in the figure 9 southwest corner. Hooper is the town in the figure 9 southwest corner near where Logan Creek joins the Elkhorn River. Tekamah is the town located in the figure 9 northeast corner. Craig is the town located near the figure 9 north center edge. Bell Creek is the south oriented stream flowing from near Craig to the figure 9 south edge. South of figure 9 Bell Creek flows to the southeast oriented Elkhorn River. South-oriented Clark Creek is located in the south half of figure 9 between the Logan Creek and Bell Creek valleys and flows to join the Elkhorn River south of the figure 9 map area. New York Creek is the south, east-southeast, and north-northeast oriented (barbed) Missouri River tributary located in the figure 9 southeast quadrant. North of New York Creek are northeast-oriented Hill and Davis Creek, which are also barbed tributaries to the south-southeast-oriented Missouri River valley. Figure 10 below provides a more detailed map of the Hill Creek-New York Creek drainage divide area. Figure 9 drainage patterns can again be best explained in the context of a massive south oriented flood moving across the entire figure 9 map area. Flood waters were moving to what was then the newly eroded southeast-, south- and east-oriented Elkhorn River-Platte River valley (and Missouri River valley downstream). The south-oriented Missouri River valley eroded north into the figure 9 map region to capture some of the south-oriented flood flow while the Bell Creek valley eroded north to capture flow to the Missouri River valley. The Clark Creek valley next eroded to capture some of the flow to the newly eroded Bell Creek valley, although headward erosion of the Logan Creek valley beheaded flood flow routes to both the newly eroded Clark Creek valley and the newly eroded Bell Creek valley. Headward erosion of the deep Missouri River valley and its tributary valleys (including the Niobrara River valley) subsequently beheaded all south- and southeast-oriented flood flow to newly eroded Elkhorn River valley.

Hill Creek-New York Creek drainage divide area

Figure 10 provides a detailed map of the Hill Creek-New York Creek drainage divide area seen in less detail in the figure 9 southeast quadrant above. New York Creek flows in a northeast and north direction from the figure 10 south center edge to enter the south-southeast oriented Missouri River valley as a barbed tributary. As seen in figure 9 west of figure 10 New York Creek is a south-oriented stream. Near the figure 10 west edge is a New York Creek tributary, which parallels the New York Creek headwaters valley (not seen in figure 10). Hill Creek flows north and east-northeast in the figure 10 northwest quadrant and continues north of the figure 10 north edge to enter the Missouri River valley as a barbed tributary. Hill Creek has several north-oriented tributaries. One of the most interesting north-oriented Hill Creek tributaries originates as a southeast-oriented stream in section 2 (in the figure 10 center area) and then turns to flow north along the section 1 west boundary and along the section 35 east boundary before joining Hill Creek. West of this north-oriented Hill Creek tributary is another north-oriented Hill Creek tributary flowing north from the figure 2 center area into section 35 where it joins Hill Creek. Note how the southeast-oriented headwaters of the first north-oriented Hill Creek tributary are linked by two separate through valleys with the second north-oriented Hill Creek tributary. Further, note how a through valley links the U-turn where the first Hill Creek tributary turns to flow north with a southeast-oriented New York Creek tributary. Also note how the first north-oriented Hill Creek tributary has a northwest-oriented tributary, which is linked by a through valley with a south-oriented New York Creek tributary. A close study of figure 10 reveals many additional through valleys crossing the present day drainage divides. These through valleys are not deep when compared with the depth of the opposing valleys on either end, but the through valleys do provide evidence of an anastomosing channel complex that existed prior to the present day drainage pattern. South-oriented flood flow across the figure 10 map area probably eroded the erosion surface into which the present day valleys are eroded. Headward erosion of the deep Missouri River valley beheaded south-oriented flood flow on the present day north-oriented New York Creek alignment. Flood waters on the north end of that beheaded flood flow route reversed flow direction to flow north and by capturing south-oriented flood flow from channels further to the west were able to erode the New York Creek valley southwest and west before headward erosion of the deep Missouri River valley beheaded and reversed flood flow to erode the northeast-oriented Hill Creek valley to the southwest.

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