Abstract:

This essay uses topographic map evidence to interpret landform origins in the Mosquito Creek-East Nishnabotna River drainage divide area located in Pottawattamie, Cass, Mills, and Montgomery Counties, Iowa. Mosquito Creek is a south-southwest oriented tributary joining the Missouri River at Council Bluffs, Iowa. The south-oriented Nishnabotna River is located east of Mosquito Creek and is formed by the convergence of several south and south-southwest oriented tributaries and joins the south-southeast oriented Missouri River in the Missouri northwest corner, just south of the Iowa southwest corner. East of the narrow south-oriented Nishnabotna River drainage basin is the narrow south-oriented Tarkio River drainage basin and east of the Tarkio River drainage basin is the somewhat longer south-southwest and south oriented Nodaway River drainage basin. The Mosquito Creek-East Nishnabotna River drainage divide area consists of multiple drainage divides between south and south-southwest oriented Nishnabotna River tributaries. Shallow through valleys eroded across present day drainage divides and northwest and north oriented barbed tributaries flowing to south-oriented streams provide evidence the Nishnabotna River and adjacent drainage routes originated when deep valleys eroded headward along what were at that time south-oriented channels in an ever-changing southeast and/or south oriented anastomosing channel complex. Flood waters were derived from a rapidly melting North American ice sheet located north of the study region and were flowing to what was then the actively eroding Missouri River valley head. The deep south-oriented valleys eroded headward in sequence from the east to west. Northwest and north oriented tributary valleys were eroded by reversals of flood flow along northwest and north ends of beheaded flood flow channels. Headward erosion of each successive south and south-southwest oriented valley beheaded at least some southeast and south oriented flood flow routes to the newly eroded valley to the east. Missouri River valley headward erosion and headward erosion of south-southwest oriented Missouri River tributary valleys, including the Mosquito Creek valley and valleys north and west of Mosquito Creek, eventually beheaded all flood flow routes to the newly formed Nisnabotna River drainage basin.

Preface:

The following interpretation of detailed topographic map evidence is one of a series of essays describing similar evidence for all major drainage divides contained within the Missouri River drainage basin and for all major drainage divides with adjacent drainage basins. The research project is interpreting evidence in the context of a previously unexplored deep glacial erosion paradigm, which is fundamentally different from most commonly accepted North American glacial history interpretations. Project essays available at this site may be found by selecting desired Missouri River tributaries and/or states from this essay’s sidebar category list.

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore the Mosquito Creek-East Nishnabotna River drainage divide area landform origins in Pottawattamie, Cass, Mills, and Montgomery Counties, Iowa, 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 essays in the Missouri River drainage basin landform origins research project 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 Mosquito Creek-East Nishnabotna River drainage divide area landform evidence in Pottawattamie, Cass, Mills and Montgomery Counties, Iowa will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm (see menu at top of page for paradigm related essay). This essay is included in the Missouri River drainage basin landform origins research project essay collection.

Mosquito Creek-East Nishnabotna River drainage divide area location map

Figure 1: Mosquito Creek-East Nishnabotna 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 Mosquito Creek-East Nishnabotna River drainage divide area. The Missouri River is the south-southeast oriented river in the figure 1 west half, and forms the boundary between Nebraska in the west and Iowa east of the Missouri River and Missouri being the state south of Iowa. Note in western Iowa numerous south-southwest oriented Missouri River tributaries. South oriented streams and rivers flowing to the figure 1 south edge east of the Missouri River are also Missouri River tributaries. South of the figure 1 map area the Missouri River turns from flowing in a south-southeast direction to flow in more of an east-oriented direction across the state of Missouri to reach the south-oriented Mississippi River. The southeast-oriented river flowing through Des Moines, Iowa in the figure 1 northeast corner area is the Des Moines River, which flows directly to the Mississippi River. The Des Moines River drainage basin is not included in the Missouri River drainage basin. Many of the south-southwest oriented Missouri River tributaries in figure 1 are not labeled. Mosquito Creek is the unlabeled south-southwest oriented tributary flowing to the Missouri River at Council Bluffs, Iowa. The Nishnabotna River is the unlabeled south-oriented river flowing through Hamburg in the Iowa southwest corner and then to the Missouri River in the Missouri northwest corner. Note how the Nishnabotna River has multiple south and south-southwest oriented tributaries. The East Nishnabotna River is the easternmost of those tributaries and flows through or near the towns of Atlantic, Griswold, and Shenandoah, Iowa. East of the East Nishnabotna River drainage basin is the narrow Tarkio River drainage basin and east of the Tarkio River drainage basin is West Nodaway River drainage basin. The Mosquito Creek-East Nishnabotna River drainage divide area in Pottawattamie, Cass, Mills, and Montgomery County discussed in this essay is located south of the towns of Avoca and Walnut and north of the town of Essex. Essays describing regions directly west and north of the Pottawattamie County and Mills County area discussed here and include the Boyer River-Mosquito Creek drainage divide area landform origins in Pottawattamie, Harrison, Shelby, and Crawford Counties essay and the Boyer River-Nishnabotna River drainage divide area landform origins in Crawford, Carroll, Shelby, and Audubon Counties essay and can be found under Iowa on the sidebar category list..

• Note in figure 1 how the Des Moines River-Missouri River drainage divide can be identified on the figure 1 map by orientations of the respective river tributaries. Missouri River tributaries in western Iowa are predominantly oriented in south and south-southwest directions while Des Moines River tributaries are oriented in southeast and northeast directions. This Des Moines River-Missouri River drainage divide is a significant landform and originated as deep valleys eroded headward into the figure 1 map area. Headward erosion of the deep valleys occurred during immense south- and southeast-oriented floods flowing across the entire figure 1 map area. Flood waters were derived from a rapidly melting thick North American ice sheet, and at the time the figure 1 drainage system evolved the ice sheet southern margin was located north of the figure 1 map area. Prior to headward erosion of the deep Missouri River valley and its deep tributary valleys into the figure 1 map area melt water floods flowed in a south direction across the entire figure 1 map area and were also being captured and diverted in a southeast direction by headward erosion of the deep Des Moines River valley and its tributary valleys. As the deep “east” oriented Missouri River valley eroded across the region south of the figure 1 map area deep south-oriented tributary valleys eroded headward from the newly eroded Missouri River valley into the figure 1 map area. As can be seen in figure 1 headward erosion of the southeast-oriented Des Moines River valley and its tributary valleys captured south-oriented flood flow moving to some of those actively eroding south-oriented Missouri River tributary valleys. Such a sequence of events would be expected if the deep Missouri River valley eroded headward from the Mississippi River valley first and was followed at a later time by Des Moines River valley headward erosion.

• The south-southeast oriented Missouri River valley seen in figure 1 was eroded along the route of a giant south and south-southeast oriented melt water river, which was emerging from the mouth of an immense southeast and south oriented ice-walled and bedrock-floored canyon which had been carved into the decaying ice sheet’s surface. The southeast and south oriented Missouri Escarpment is what remains of that ice-walled and bedrock-floored canyon’s west and southwest wall and can be traced from southern South Dakota north and northwest into Alberta, which suggests the melt water river flowing on the floor of the ice-walled canyon was draining a significant region of the decaying ice sheet’s surface. Before being captured by headward erosion of the deep Missouri River valley melt water floods emerging from that ice-walled canyon not only flowed in a south-southeast direction to the actively eroding Missouri River valley, but also flowed in a southeast direction toward the actively eroding Des Moines River valley (and tributary valleys) and to south-oriented Missouri River tributary valleys (east of the south-southeast oriented Missouri River valley). As the Missouri River valley eroded headward into the figure 1 map area south and south-southwest oriented tributary valleys eroded headward from the actively eroding Missouri River valley head to capture the south- and southeast-oriented flood flow and to divert the flood waters to the actively eroding Missouri River valley head. These tributary valleys and their tributary valleys eroded headward in sequence from east to west. In the region of concern in this essay the Nodaway River valley eroded headward first and was followed by Tarkio River valley headward erosion. Nishnabotna River valley headward erosion was next and Mosquito Creek valley and then Boyer River valley headward erosion followed, with each successive valley beheading flood flow routes to the newly eroded valley just to the east. Probably all valleys were eroding headward at the same time with the easternmost valleys eroding headward slightly in advance of more western valleys.

Detailed location map for Mosquito Creek-East Nishnabotna River drainage divide area in Pottawattamie, Cass, Mills, and Montgomery Counties.

Figure 2: Detailed location map for Mosquito Creek-East Nishnabotna River drainage divide area in Pottawattamie, Cass, Mills, and Montgomery Counties. United States Geological Survey map digitally presented using National Geographic Society TOPO software. .

Figure 2 provides a detailed location map of the Pottawattamie, Cass, Mills, and Montgomery County area in western Iowa. The county names and boundaries are shown. The south-southeast oriented Missouri River is located near the figure 2 west edge. Omaha, Nebraska is the large city directly west of Council Bluffs. Mosquito Creek flows in a south-southwest from Neola in northern Pottawattamie County to join the Missouri River at Council Bluffs. North and west of Mosquito Creek is southwest-oriented Pigeon Creek and the south-southwest oriented Boyer River in the figure 2 northwest corner. Immediately east of Mosquito Creek is south-southwest oriented Keg Creek and east of Keg Creek is south-southwest oriented Silver Creek. The West Nishnabotna River flows in a south-southwest direction through Hanncock in Pottawattamie County and Hastings and Mills County. The East Nishnabotna River is the south-southwest oriented river flowing through Atlantic in Cass County and Red Oak in Montgomery County. The West Nodaway River originates near Massena in southeast Cass County and flows in a southwest direction to Grant in the Montgomery County northeast corner and then in a south direction in eastern Montgomery County. Between the East Nishnabotna River and the West Nodaway River in Montgomery County are the south-oriented Tarkio River and its south-oriented West Tarkio Creek tributary (west of the Tarkio River). Note how all major drainage routes in the Pottawattamie, Cass, Mills, and Montgomery County area are oriented in south and south-southwest directions and how most drainage basins are extremely narrow. These narrow drainage basins suggests the stream valleys were initially eroded as channels in a flood formed south and south-southwest oriented anastomosing channel complex. While not apparent from the figure 2 map evidence, but which will become apparent in topographic maps below, this south and south-southwest oriented anastomosing channel complex eroded headward across what was probably a southeast-oriented flood formed anastomosing channel complex. The south-oriented valleys in the figure 2 map area, as previously described, eroded headward in sequence from east to west, with each successive valley eroding headward slightly behind the valley immediately to the east and beheading southeast-oriented flood flow to the newly eroded valley to the east. Probably all valleys were eroding headward at the same time, which means at one time all valleys in the southern half of the figure 2 map area were simultaneously carrying flood water while in the figure 2 north half actively eroding valleys in the east were still capturing southeast-oriented flood flow moving across regions further to the west. The discussion in this essay will first look at drainage divides between Mosquito Creek and East Nishnabotna River in Pottawattamie and Cass Counties and will conclude with a look at drainage divides between the West Nishnabotna River and the West Nodaway River in Mills and Montgomery Counties.

Mosquito Creek-West Nashnabotna River drainage divide area

Figure 3: Mosquito Creek-West Nashnabotna River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 provides a topographic map of the Mosquito Creek-West Nishnabotna River drainage divide area in northern Pottawattamie County. Mosquito Creek is the south-southwest oriented stream located in the figure 3 northwest corner and Neola is the town located in the Mosquito Creek valley. Keg Creek is the south-southwest oriented stream east of Mosquito Creek and flowing from the figure 3 north edge (west half) to the figure 3 south edge (near southwest corner). Mosquito Creek and Keg Creek each flow independently to the Missouri River. Little Silver Creek is located east of Keg Creek and originates near the figure 3 center and flows to the figure 3 south edge (west half). Middle Silver Creek is located east of Little Silver Creek and flows in a south-southwest direction from the figure 3 north edge (slightly east of center) to the figure 3 south half (slightly west of center). Silver Creek is the south-southwest oriented stream located east of Middle Silver Creek and flows from the figure 3 north edge (east half) to the figure 3 south edge (slightly east of center). The West Nishnabotna River is the south-southwest oriented river located along the figure 3 east edge and Oakland is the town in the figure 3 southeast corner. Slocum Creek is the south-southeast oriented tributary joining the West Nishnabotna River just south of the figure 3 map area. South of the figure 3 map area Little Silver Creek joins Middle Silver Creek and Middle Silver Creek then joins Silver Creek, which subsequently joins the West Nishnabotna River. Note how almost all drainage routes in the figure 3 map area are oriented in a south-southwest direction and have very narrow drainage basins. Also note how all of the south-southwest oriented streams have at least some barbed northwest-oriented tributaries. These barbed tributaries are especially evident in the figure 3 northwest quadrant, although can be found throughout the map. Study of the figure 3 map area reveals shallow through valleys eroded across drainage divides often linking headwaters of northwest-oriented tributaries with headwaters of south-oriented tributaries to the south-southwest oriented stream immediately to the east. These through valleys are best seen on more detailed topographic maps and figure 4 below illustrates a detailed topographic map of the Silver Creek-Slocum Creek drainage divide area. The through valleys provide evidence of flood flow channels that existed prior to headward erosion of deep south-southwest valleys further to the west and north. The northwest-oriented and barbed tributary valleys were eroded by reversals of flood flow when those flood flow channels were beheaded by headward erosion of the deep south-southwest oriented valley into which the tributaries now flow.

Detailed map of Silver Creek-Slocum Creek drainage divide area

Figure 4: Detailed map of Silver Creek-Slocum 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 Silver Creek-Slocum Creek drainage divide area seen in less detail in the figure 3 map area above. Silver Creek is labeled and flows in a south, west, southwest, and south-southwest direction from the figure 4 north edge (slightly west of center) to the figure 4 west edge (slightly south of center). The south-southwest oriented West Nishnabotna River valley is visible in the figure 4 southeast corner. Slocum Creek flows in a south direction near the boundary between sections 27 and 28 (just south of the word JAMES) to the figure 4 south edge and joins the West Nishnabotna River south of the figure 4 map area. Note how the Slocum Creek valley is linked by shallow through valleys with the Silver Creek valley. For example, in the section 21 center area a northwest-southeast oriented through valley links the Silver Creek elbow of capture (where Silver Creek turns from flowing in south direction to flowing in a west direction) with the Slocum Creek elbow of capture (where Slocum Creek turns from flowing an east direction to flowing in a southeast and south-southeast direction). The map contour interval is ten feet and the through valley floor elevation is between 1210 and 1220 feet. The hill immediately to the southwest (in section 21 southwest quadrant) rises to at least 1260 feet and the hill in the section 21 northeast quadrant rises to more than 1270 feet. However continuing along the drainage divide further to the southwest and to the northeast elevations rise to at least 1300 feet (in the section 29 northeast quadrant and along the figure 4 north edge just north of the section 22 northwest quadrant). The through valley is a water eroded feature and was eroded by south-southeast oriented flood flow prior to headward erosion of the deep Silver Creek valley. At the time the through valley was eroded flood waters were flowing to what was then the actively eroding Slocum Creek valley, which had eroded headward from what was then the newly eroded West Nishnabotna River valley. Numerous other through valleys can be found crossing all figure 4 drainage divides. Another very different example can be found in the section 29 northeast quadrant where a through valley links the northeast-oriented Slocum Creek headwaters with headwaters of a southwest and west oriented Silver Creek tributary. The through valley floor elevation is between 1290 and 1300 feet and elevations on either side rise to more than 1300 feet, suggesting the through valley is very shallow. However the through valley exists and provides evidence that for a time southwest-oriented flood flow moved across the top of what is today a hill. To properly understand that through valley it is important to understand that flood waters moving across the figure 4 map area were moving in anastomosing channels, where channels not only converged, but also diverged. The southwest-oriented flood flow channel across that present day section 29 hill-top was first moving to the actively eroding Silver Creek valley, Next the flood flow channel was captured by headward erosion of the deep south-oriented Slocum Creek valley, which reversed flood flow to erode the northeast oriented Slocum Creek headwaters valley. Shortly after Silver Creek valley headward erosion beheaded the southeast-oriented flood flow channel, which by that time had eroded the section 21 through valley.

West Nishnabotna River-East Nishnabotna River drainage divide area

Figure 5: West Nishnabotna River-East Nishnabotna River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 5 provides a topographic map of the West Nishnabotna River-East Nishnabotna River drainage divide area south and east of the figure 3 map area. Oakland is the town in the figure 5 northwest corner and is located on the east edge of the West Nisnabotna River valley. Griswold is the town located near the figure 5 east center edge and is located in the East Nishnabotna River valley. Immediately east of Oakland in the figure 5 northwest corner area is an unnamed south-southwest oriented West Nishnabotna River tributary, headwaters of which will be seen in figure 6 below. East of that unnamed West Nishnabotna River is south-southwest and south oriented Graybill Creek which is labeled on figure 5. East of Graybill Creek is south-oriented Spring Creek, which is a tributary to the much longer south-southwest oriented Jordan Creek. Originating in the figure 5 center area is south-southwest and southwest oriented Farm Creek (the word “Farm” is not visible in figure 5). South of the figure 5 map area Graybill Creek and Jordan Creek join Farm Creek, which then flows to the West Nishnabotna River. East of Farm Creek, and also originating in the figure 5 map area, is south, southwest, and south oriented Indian Creek, which is another West Nishnabotna River tributary and which will be seen again in figure 9 below. East of Indian Creek is south oriented Walnut Creek, which is unlabeled in figure 5 and which will be seen again in figure 9 below. South of the figure 5 map area Walnut Creek continues to flow in a valley near and parallel to the East Nishnabotna River valley for a considerable distance, but finally turns to the flow in a southwest direction to join the West Nishnabotna River slightly north of where the West and East Nishnabotna River join to form the Nishnabotna River. A close look at the figure 5 map reveals short northwest oriented tributaries or tributary valleys to many of the south-oriented trunk streams from the east and short southeast-oriented tributaries from the west. The figure 5 drainage pattern is again one of roughly parallel south and south-southwest oriented and closely spaced streams with very narrow drainage basins. Streams originating in the figure 5 map area for the most part are also south or south-southwest oriented and are linked by shallow through valleys with adjacent deeper valleys. The figure 5 drainage pattern again suggests it originated as a south-oriented anastomosing channel complex. The short northwest and southeast-oriented tributary valleys suggest headward erosion of the deep south oriented valleys beheaded southeast-oriented flood flow channels, with northwest-oriented tributary valleys being eroded by reversals of flood flow on northwest ends of beheaded flood flow routes.

Detailed map of West Nishnabotna River-Graybill Creek drainage divide area

Figure 6: Detailed map of West Nishnabotna River-Graybill 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 West Nishnabotna River-Graybill Creek drainage divide area located north and east of Oakland and just north of the figure 5 northwest corner and east of the figure 3 southeast corner. Oakland is located in the figure 6 southwest corner. The south-oriented West Nishnabotna River is located near the figure 6 west edge. Graybill Creek is the labeled stream flowing from the figure 6 northeast corner to the figure 6 south edge (east half). Of special interest is the southwest-oriented stream originating in the section 33 southwest quadrant and flowing across the section 32 southeast corner, section 5 west half, section 8 east half, and section 7 southeast corner. Note how that unnamed stream, which was pointed out in the figure 5 discussion, is linked by multiple shallow northwest-southeast oriented through valleys with northwest-oriented West Nishnabotna River tributary valleys. For example in the section 32 southeast quadrant a through valley links the unnamed southwest-oriented stream valley with a northwest-oriented West Nishnabotna River tributary valley. The map contour interval is ten feet and the through valley is defined by three contour lines on each side. Another through valley can be seen near the center of the section 6-section 7 boundary in the figure 6 southwest quadrant. That through valley links a south-oriented tributary to the larger unnamed stream with a another northwest-oriented West Nishnabotna River tributary. Still another and even shallower through valley can be seen in the section 5 east half and links a southeast-oriented tributary valley with still another northwest-oriented West Nishnabotna River tributary valley. Similar shallow through valleys can be seen along the drainage divide between the unnamed southwest-oriented stream and the Graybill Creek valley. Note how many Graybill Creek tributaries from the west are oriented in southeast directions and from the east are oriented in northwest directions. The through valleys provide further evidence of diverging and converging flood flow channels typical of flood formed anastomosing channel complexes. The northwest-oriented barbed tributaries flowing to south-oriented rivers and streams can best be explained by reversals of southeast-oriented flood flow on northwest ends of beheaded flood flow channels.

East Nishnabotna River-West Nodaway River drainage divide area

Figure 7: East Nishnabotna River-West Nodaway River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 7 provides a reduced size topographic map of the East Nishnabotna River-West Nodaway River drainage divide area east and somewhat north of the figure 5 map area. Griswold is located a short distance west of the figure 7 southwest corner area. Lewis is the town located near the figure 7 west center edge. The East Nishnabotna River is the south-southwest oriented river flowing from the figure 7 north edge (near northwest corner) to the figure 7 west edge near Lewis. Turkey Creek is the southwest-oriented stream joining the East Nishnabotna River a short distance north of Lewis. Labeled northwest-oriented Turkey Creek tributaries with southwest-oriented headwaters from west to east are Bear Branch, Lone Tree Branch, and Jim Branch. Massena is the town located near the east edge in the figure 7 southeast quadrant. The West Nodaway River flows in a west and southwest direction across the figure 7 southeast quadrant and is located just south of Massena. Sevenmile Creek is the southwest-oriented stream flowing from the figure 7 northeast corner to the south center region where it turns to flow in a northwest direction before turning again to flow in a south direction to the figure 7 south edge (west half). South of the figure 7 map area Sevenmile Creek joins the West Nodaway River, which then flows in a south direction parallel to the south-oriented East Nishnabotna River (see figure 2). Fourmile Creek is the southwest, west-northwest, and south-southwest oriented Sevenmile Creek tributary located south of Bear Branch. Note how shallow through valleys cross drainage divides. Again, the through valleys are better seen on more detailed topographic maps, but can be seen crossing many of the figure 7 drainage divides. For example note shallow through valleys crossing the Lone Tree Branch-Bear Branch drainage divide. Then proceed to the Bear Branch-Fourmile Creek drainage divide and note how through valleys cross that divide also,. The through valleys provide evidence for a major south-oriened flood flow route which was progressively captured by headward erosion of deep East Nishnabotna River tributary valleys. Initially the south-oriented flood flow was moving to the south-oriented West Nodaway River-Sevenmie Creek-Fourmile Creek valley. Headward erosion of the deep East Nishnabotna River-Turkey Creek valley next beheaded and reversed the flood flow to erode the northwest-oriented Bear Branch valley segment. Next headward erosion of the Turkey Creek-Lone Tree Branch valley beheaded and reversed the flood flow to erode the northwest-oriented Lone Tree Branch valley segment. Similar histories can be reconstructed based on valley orientations and through valleys for all other figure 7 drainage routes.

Detailed map of Bear Branch-Fourmile Creek drainage divide area

Figure 8. Detailed map of Bear Branch-Fourmile Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 8 shows a reduced size detailed topographic map of the Bear Branch-Fourmile Creek drainage divide area seen in less detail in figure 7 above. Lewis is the town in the figure 8 northwest quadrant and the East Nishnabotna River flows in a southwest direction across the figure 8 northwest corner and then meanders in a south direction along the figure 8 west center edge. Bear Branch flows in a west direction across the figure 8 northeast quadrant and then turns to flow in a northwest direction to the figure 8 north center edge. North of the figure 8 map area Bear Branch joins Turkey Creek which then joins the East Nishnabotna River. Note how Bear Branch has several north and northwest oriented tributaries. Fourmile Creek is the labeled south-southwest and south oriented stream near the east edge of the figure 8 southeast quadrant. South of the figure 8 map area Fourmile Creek flows to south-oriented Sevenmile Creek, which then flows to the south-oriented West Nodaway River (see figures 7 and 2). The unlabeled south-oriented stream in section 19 is another Sevenmile Creek tributary. Note how the south-oriented Sevenmile Creek tributary valleys are linked by through valleys with the north-oriented Bear Branch tributary valleys. For example in the section 18 west half a well-defined through valley links a north-oriented Bear Branch tributary valley with the valley of the unlabeled south-oriented Sevenmile Creek tributary. The map contour interval is 20 feet and the through valley is defined by three contour lines on each side. Shallower through valleys (defined by only one or two contour lines on each side) can be seen in the section 13 northeast quadrant, section 17, and along the sections 9 and 10 south boundary. While not deep and certainly not spectacular geomorphology evidence, these multiple through valleys provide evidence of multiple south-oriented flood flow channels, which once moved large quantities of south-oriented flood water into the actively eroding Sevenmile Creek valley and tributary valleys. At that time the Bear Branch valley did not exist nor did other valleys north of the figure 8 map area exist. Flood waters were free to flow from the decaying ice sheet margin into the figure 8 map area to the actively eroding Sevenmile Creek tributary valleys. The south-oriented flood flow was then beheaded by headward erosion of the deep East Nishnabotna River-Turkey Creek valley. Flood waters on the north and northwest ends of the beheaded flood flow routes reversed flow direction to erode the northwest-oriented Bear Branch valley segment and north-oriented Bear Branch tributary valleys in sections 7 and 18. The Bear Branch valley then eroded headward across south-oriented flood flow channels and flood waters on north ends of beheaded flood flow routes reversed flow direction to erode north-oriented Bear Branch tributary valleys.

Indian Creek-Walnut Creek drainage divide area

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

Figure 9 provides a topographic map of the Indian Creek-Walnut Creek drainage divide area and is located in the Mills-Montgomery County boundary area south and somewhat west of the figure 5 map area. Hastings is the town located near the figure 9 west edge and is located on the east edge of the West Nishnabotna River river valley. Red Oak is the much larger town straddling the figure 9 east edge and is located along the East Nishnabotna River east bank. Emerson is the town located between Hastings and Red Oak and is located near the elbow of capture where south-southwest oriented Indian Creek turns to flow in a west direction to join the West Nishnabotna River near Hastings. The north-south oriented Mills-Montgomery County line is located just east of Emerson with Emerson and Hastings being located in Mills County and Red Oak in Montgomery County. Walnut Creek is the south-southwest oriented stream located west of the East Nishnabotna and Crabapple Creek is the south-southwest and southeast oriented stream joining Walnut Creek near Hawthorne (a place-name in the region between Emerson and Red Oak). The West Nishnabotna-East Nishnabotna River drainage divide area, including Walnut Creek and Indian Creek, was seen further to the north in the figure 5 map area. Note how the south-southwest and south oriented streams have maintained their separate routes and narrow drainage basins. Evidence for shallow through valleys can be seen on the figure 9 map, although more detailed topographic maps show the through valleys better. For example in the figure 9 northwest quadrant south of the words “WILLOW SLOUGH GAME MANAGEMENT AREA” at least two through valleys can be seen linking northwest-oriented West Nishnabotna River tributary valleys with south-oriented Indian Creek tributary valleys. The present day valley orientations and through valleys provide evidence of what was once an ever-changing south-oriented anastomosing channel complex where the south-oriented flood flow channels both diverged and converged. The present day figure 9 drainage pattern evolved as deep valleys eroded headward along the most successful of the south-oriented channels. The deep valleys were eroded headward by flood waters entering the actively eroding valleys further to the north. The south-southwest oriented streams originating south of the west-oriented Indian Creek valley segment (between Emerson and Hastings) are headwaters of south-southwest oriented Deer Creek, which is a West Nishnabotna River tributary. Note how the south-oriented Deer Creek headwaters valleys are linked by shallow through valleys with north-oriented Indian Creek tributary valleys and also with a northwest oriented West Nishnabotna River tributary (flowing to the West Nishnabotna River valley near Hastings). Again, the valley orientations and through valleys provide more evidence of the former anastomosing channel complex.

East Nishnabotna River-West Nodaway River drainage divide area

Figure 10: East Nishnabotna River-West Nodaway River drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 illustrates the East Nishnabotna River-West Nodaway River drainage divide area located east of the figure 9 map area and includes overlap areas with figure 9. Red Oak is the town located in the figure 10 southwest corner. Stanton is the much smaller town located near the figure 10 south center edge. Walnut Creek is the south-southwest oriented stream in the figure 10 northwest corner. As previously mentioned Red Oak is located on the east bank of the south-southwest and south oriented East Nishnabotna River. The south-southwest and south oriented river flowing to the figure 10 south center edge (just west of Stanton) is the Tarkio River. The West Tarkio River originates in the region between Red Oak and the Tarkio River and flows in a south direction to the figure 10 south edge. The south-oriented river located near the figure 10 east edge is the West Nodaway River. The south-southeast oriented stream joining the West Nodaway River in the figure 10 northeast corner area is Sevenmile Creek. Note how the south-oriented West Nishnabotna River has several northwest oriented tributaries and how headwaters of at least two of those northwest-oriented tributaries are linked by shallow through valleys with the south-oriented West Tarkio River valley, which is also linked by shallow through valleys with the south-oriented Tarkio River valley. These shallow through valleys provide additional evidence of the diverging and converging flood flow channels which existed prior to headward erosion of the deeper south-oriented trunk stream valleys seen today. Little Tarkio Creek is the south and southwest oriented stream joining the Tarkio River near Stanton (along the figure 10 south center edge). Note how the Little Tarkio Creek valley is linked by a shallow through valley with an east-northeast oriented Sevenmile Creek tributary valley. Again the through valley provides evidence of a former flood flow channel that diverged from the Sevenmile Creek alignment and led to the Tarkio River alignment. Today the Nodaway River, Tarkio River, and Nishnabotna River all flow independently to the Missouri River. However, prior to headward erosion of the deep south-oriented valleys the figure 10 map area was crossed by an ever-changing southeast and south oriented anastomosing channel complex. The shallow through valleys are abundant in the figure 10 map area, but as already mentioned are easier to see on more detailed topographic maps. Readers wanting to work out more drainage history events are encouraged to study mosaics of detailed topographic maps illustrating the Mosquito Creek-East Nishnabotna River drainage divide area.

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.