A geomorphic history based topographic map evidence

The Middle Loup River-Mud Creek drainage divide area in Custer, Valley, Sherman Counties, Nebraska was eroded by an immense southeast-oriented flood that flowed across the entire drainage divide area. Initially flood waters flowed across a topographic surface at least as high as the highest drainage divide elevations today. It is possible flood waters deposited sediments in the Middle Loup River-Mud Creek drainage divide area, although topographic map evidence alone is not adequate to make such a determination. Whether drainage divide area sediments were flood deposited or were deposited prior to the flood, the sediments were easily eroded and flood waters deeply eroded the entire region as the deep Middle Loup River, Mud Creek, and tributary valleys eroded headward into the present day drainage divide area. Evidence for the southeast-oriented flood flow and headward erosion of the present day valleys includes orientations of present day valleys, numerous through valleys crossing present day drainage divides, barbed tributaries to major valleys, anastomosing channel complexes, and streamlined erosional residuals.

• The purpose of this essay is to use topographic map interpretation methods to explore Middle Loup River-Mud Creek drainage divide area landform origins in Custer, Valley, and Sherman 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 the 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 Middle Loup River-Mud Creek drainage divide area landform origins in Custer, Valley, and Sherman 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.

Middle Loup River-Mud Creek drainage divide area location map

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

Figure 1 provides a location map for the Middle Loup River-Mud Creek drainage divide area in Custer, Valley, and Sherman Counties, Nebraska. Figure 1 illustrates an area in central Nebraska. The North and South Platte Rivers flow from the figure 1 west edge area to join at North Platte where the combined flow forms the Platte River. From North Platte the Platte River flows in a southeast direction to Kearney (in the figure 1 south center) and at Kearney the North Platte River turns to flow in a northeast direction to Columbus near the figure 1 east edge. East of figure 1 the Platte River turns to flow in a south and then an east direction to join the Missouri River. Joining the Platte River at Columbus is the northeast-oriented Loup River, which flows north of and roughly parallel to the northeast-oriented Platte River valley segment from the Grand Island area to Columbus. Major Loup River tributaries are southeast oriented and include (from east to west) Beaver Creek, Cedar River (unlabeled in figure 1, but flowing through Spalding and Cedar Rapids), North Loup River, Middle Loup River, Mud Creek (unlabeled in figure 1, but the unlabeled stream flowing from Broken Bow to Litchfield and joining the Loup River at Ravenna and into which Clear Creek flows), and the South Loup River. The Loup River-Platte River drainage divide area between Kearney and Columbus essay addresses the region located south of the Middle Loup River-Mud Creek drainage divide area; the North Loup River-Middle Loup River drainage divide area essay addresses the region east of the Middle Loup River-Mud Creek drainage divide area; and the Elkhorn River-Loup River drainage divide area in Rock, Holt and Garfield Counties and the Niobrara River-North Loup River drainage divide area essays address the region found north and west of the Middle Loup River-Mud Creek drainage divide area and can be found under Loup River on the sidebar category list. These and hundreds of other Missouri River drainage basin landform origins research project essays published on this website have built a strong case for immense southeast-oriented floods that once moved across the entire figure 1 map area. Essays can be used to trace the southeast-oriented floods headward into north central Montana and southern Alberta. A case is also built that these immense southeast-oriented floods encountered massive east-oriented floods in central Nebraska and flood waters may have been ponded as flood waters from different sources (or that used two very different routes from the same source to reach central Nebraska) converged. Headward erosion of what was then a deep northeast-oriented Loup River-Platte River valley captured the flood waters and diverted the water east to what was then the newly eroded southeast-oriented Missouri River valley. Today the northeast-oriented Loup River flows along the northwest of the large northeast-oriented Loup River-Platte River valley and the Platte River flows along the valley’s southeast margin. The Loup River channel is where southeast-oriented flood waters entering the newly eroded northeast-oriented were forced to flow by flood waters from further west, which were forced to flow along the valley’s southeast wall. Present day southeast-oriented Loup River tributary valleys eroded headward from this newly eroded and deep northeast-oriented Loup River-Platte River valley and created the central Nebraska topographic relief seen today.

Middle Loup River-Mud Creek drainage divide area detailed location map

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

Figure 2 provides a more detailed location map for the Middle Loup River-Mud Creek drainage divide area in Custer, Valley, and Sherman Counties. Logan, Custer, Valley, and Sherman are Nebraska county names and the county boundaries are shown. The Middle Loup River flows in a southeast direction from Dunning (just east of the National Forest area in the figure 2 northwest corner) into northern Custer County and then across the Valley County southwest corner before flowing diagonally across Sherman County to the figure 2 east edge. Mud Creek originates northwest of Broken Bow (located in central Custer County) and flows in a southeast direction to cross the Sherman County southwest corner and then joins east-northeast oriented South Loup River to join the Middle Loup River just east of the figure 2 map area. East of figure 2 the combined flow forms the northeast-oriented Loup River, which flows eventually to reach the Platte River near Columbus (see figure 1). Some important Middle Loup River tributaries illustrated and discussed below include north-oriented Victoria Creek, Lillian Creek, and Wagner Creek. An important Mud Creek tributary in the discussion below is Clear Creek (note on the location maps Mud Creek downstream from it confluence with Clear Creek is labeled Clear Creek, however in the detailed maps it is labeled Mud Creek). Almost all Loup River tributaries and tributaries to those tributaries shown in figure 2 are southeast or south oriented and provide evidence of an immense southeast or south oriented flood that eroded the figure 2 map area (at least the eastern two-thirds of the figure 2 map area). This predominance of southeast and south oriented drainage routes is evidence of massive southeast or south oriented floods that flowed across the figure 2 map area and which was responsible for headward erosion of the present day valleys.  Exceptions are barbed tributaries and include north-oriented tributaries to the Middle Loup River, such as Victoria Creek, Dry Creek, Lillian Creek, and Wagner Creek among others. These north-oriented tributary valleys were eroded by reversals of flood water on the north ends of south-oriented flood flow routes beheaded by headward erosion of what was then the deep Middle Loup River valley. Some of these barbed tributaries are illustrated in greater detail in figures below. Other evidence supporting the massive southeast or south oriented flood interpretation includes through valleys crossing present day drainage divides and anastomosing channel complexes. The through valleys provide evidence of multiple flood flow routes that once crossed the modern-day drainage divides. The anastomosing channel complexes were eroded when multiple flood flow channels crossed the region.

Victoria Creek-North Branch Mud Creek drainage divide area

Figure 3: Victoria Creek-North Branch Mud Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 3 illustrates the Victoria Creek-North Branch Mud Creek drainage divide area at the northwest end of the Middle Loup River-Mud Creek drainage divide area investigated in this essay. Anselmo is the town located in the figure 3 northwest corner area. Merna is the town located near where the highway and railroad cross the figure 3 south edge. New Helena is the small town (or place-name) located near Victoria Spring State Recreation Area in the figure 3 north center area. The southeast-oriented Middle Loup River can be seen in the figure 3 northeast corner. Victoria Creek originates southeast of Anselmo and flows in a southeast direction in the New Hope Valley before turning to flow in a northeast direction to New Helena and then to the Middle Loup River north of the figure 3 map area. Note how the northeast-oriented Victoria Creek valley has southeast-oriented tributaries including Cedar Canyon and the New Hope Valley and also has north and northwest oriented tributary valleys, including northwest-oriented Pleasant Valley (south of New Helena). The northeast-oriented Victoria Creek valley eroded headward from what was at one time the actively eroding Middle Loup River valley head to capture yet to be beheaded southeast-oriented flood flow routes south and west of the Middle Loup River valley head. The southeast-oriented tributary valleys were eroded headward from the newly eroded northeast-oriented Victoria Creek valley. The north and northwest oriented tributary valleys were eroded by reversals of flood flow on the north and northwest ends of beheaded south and southeast oriented flood flow routes. The reversed flood flow flowed north and northwest to the newly eroded and deeper northeast-oriented Victoria Creek valley. Note how some of these north-oriented Victoria Creek tributaries are linked by north-south and northwest-southeast oriented through valleys with the large southeast-oriented Dale Valley, in which Merna is located along the northeast edge. The South Branch Mud Creek flows across the Dale Valley to the Broken Bow area (seen in figure 4) and headward erosion of the northeast-oriented Victoria Creek valley beheaded southeast-oriented flood flow that was moving to what was then the actively eroding Mud Creek valley. But, what is just as interesting is where the South and North Branches of Mud Creek originate. Instead of originating in Dale Valley they originate on the west edge of East Table, which is the high tableland located just east of Merna. Figure 3a below provides a detailed map of the South and North Branch Mud Creek headwaters area. The South Branch originates in section 4 and flows southwest across the Dale Valley before joining the North Branch near Broken Bow. The North Branch originates in section 3 and flows in a southeast direction to join the South Branch near Broken Bow. These two valleys were eroded headward by south and southeast oriented flood water that flowed across the East Table upland surface. Note the northwest-oriented valleys in sections 33 and 34, which were eroded by reversals of flood flow when headward erosion of the Victoria Creek valley beheaded the southeast-oriented flood flow. This figure 3 and figure 3a evidence provides some clues as to the magnitude of flood flow involved and also as to the magnitude of flood erosion that occurred. The depressions  on the East Table upland surface are probably flood related features and figure 10a below illustrates similar depressions in an easier to identify flood eroded channel. Before leaving figure 3 note north-oriented Dry Creek and Lilian Creek east of the northeast-oriented Victoria Creek valley segment. Also note headwaters of southeast-oriented Clear Creek east of the East Table upland.
Figure 3a: Mud Creek headwaters located east of Merna and along west edge of East Table. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Clear Creek-Mud Creek drainage divide area

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

Figure 4 is located south and east of the figure 3 map area and includes overlap areas with figure 3. East Table is located along the figure 4 west edge (north half). Broken Bow is the town located in the figure 4 southwest quadrant. The southeast-oriented North Branch Mud Creek flows from the figure 4 west center edge (just south of East Table) to Broken Bow, where it joins the east-oriented South Branch Mud Creek to form southeast-oriented Mud Creek. Deadman Canyon located east of East Table flows to northeast-oriented Clear Creek, which in the figure 4 north center area turns to flow in a southeast direction to the figure 4 east center edge. North of Deadman Canyon are southeast-oriented headwaters of north-oriented Lilian Creek (seen in figure 3). Note how the northeast-oriented Clear Creek segment east of Deadman Canyon has multiple northwest-oriented tributaries. The southeast-oriented Lilian Creek headwaters and the northwest-oriented Clear Creek tributaries are evidence that deep valleys eroded headward across multiple southeast-oriented flood flow routes or channels. The northwest-oriented tributaries are evidence of flood reversals on the northwest ends of beheaded southeast-oriented flood flow routes. Also note Tappan Valley just north of Broken Bow. Tappan Valley is a large northwest-southeast oriented valley, which drains to southeast-oriented Mud Creek. Tappan Valley was eroded by southeast-oriented flood water that was beheaded by headward erosion of the east-oriented Deadman Canyon valley. A close look at the Deadman Canyon-Tappan Valley drainage divide reveals multiple through valleys, which provide evidence of former channels used by south-oriented flood water moving to the actively eroding Tappan Valley just prior to headward erosion of the Clear Creek-Deadman Canyon valley to the north. Figure 4a below provides a detailed map of the Deadman Canyon-Tappan Valley drainage divide area. The East Table upland surface is located in the figure 4a northwest corner. The northwest-southeast oriented road in section 5 (figure 4a) uses a deeper through valley to cross the Deadman Canyon-Tappan Valley drainage divide, although many other through valleys at various higher elevations are present on either side of the road including some other deep through valleys used by roads in sections 4 and 9. Headward erosion of the northeast-oriented Clear Creek valley and its east-oriented Deadman Canyon tributary valley beheaded the south-oriented flood flow moving to Tappan Valley and Mud Creek.
Figure 4a: Detailed map illustrating through valleys across the Deadman Canyon-Tappan Valley drainage divide. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Wagner Creek-Clear Creek drainage divide area

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

Figure 5 illustrates the Wagner Creek-Clear Creek drainage divide area east and north of the figure 4 map area and includes overlap areas with figure 4. Comstock is the town located in the figure 5 northeast quadrant and is located in the south-southeast oriented Middle Loup River valley. North and west of the figure 5 map area the Middle Loup River is east-southeast oriented, and south and east of the figure 5 map area the Middle Loup River is southeast-oriented. Wagner Creek is the north, northeast, and east oriented Middle Loup River tributary in DOUGLAS GROVE township. Note how Wagner Creek tributaries east of the northwest-southeast oriented Dry Valley (in the figure 5 center area) are northwest oriented. Spring Creek is the southeast, north-northeast, and east oriented Middle Loup tributary in the figure 5 southeast quadrant. The southeast-oriented stream in the figure 5 southwest quadrant is Clear Creek. French Tableland and Boggs Table in the figure 5 west half provide evidence of an upland surface that existed prior to headward erosion of the deep Middle Loup River, Clear Creek, and Mud Creek valleys. Prior to headward erosion of those deep southeast-oriented valleys the figure 5 map area was at least as high as the French Tableland and Boggs Table elevations if not higher. It is possible flood waters deposited sediments in this area and if so some of those sediments may be preserved on the French Tableland and Boggs Table upland surfaces. Erosion of the figure 5 map area occurred as headward erosion of the deep southeast-oriented Clear Creek valley and the southeast-oriented Middle Loup River valleys reached the figure 5 map region. Southeast-oriented flood flow eroded the northwest-southeast oriented valleys headward to the French Tableland and Boggs Table southeast-facing escarpment while the present day Clear Creek valley was being eroded around the French Tableland south end. A Clear Creek tributary then eroded a deep southwest and south oriented valley headward along the west margin of the French Tableland and Boggs Table to behead flood flow routes moving across the French Tableland and Boggs Table upland surface. In other words the French Tableland and Boggs Table southeast-facing escarpment is the head of a large abandoned headcut that was being eroded by southeast-oriented flood water. Note evidence of anastomosing channels and streamlined erosional residuals southeast of that abandoned headcut face. Figure 6 below provides a more detailed map of the Wagner Creek-Clear Creek drainage divide area immediately southeast from Boggs Table  at the Dry Valley northwest end.

Detailed map of Wagner Creek-Clear Creek drainage divide area

Figure 6: Detailed map of Wagner Creek-Clear 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 Wagner Creek-Clear Creek drainage divide area east of Boggs Table and seen in less detail in figure 5 above. The Boggs Table upland surface is located in the figure 6 northwest corner and west center edge area, Northwest-southeast oriented Dry Valley is located east of Boggs Table and extends from the figure 6 north center area to the figure 6 southeast corner and beyond (to the Clear Creek valley-see figure 7 below). Wagner Creek originates in the figure 6 north center area and flows in a northwest, northeast, southeast, and northeast direction to the figure 6 east edge (north half). Note the northwest-oriented Wagner Creek headwaters in sections 21 and 28 and also how Wagner Creek has southeast-oriented headwaters on the Boggs Table slope in section 20. Figure 6 evidence demonstrates the Wagner Creek valley eroded headward from what was then the deep and newly eroded southeast-oriented Middle Loup River valley to capture southeast-oriented flood water moving across a topographic surface equivalent in elevation to the present day Boggs Table upland surface elevation. In doing so the Wagner Creek valley beheaded southeast-oriented flood flow that was actively eroding the large southeast-oriented Dry Valley headward into the figure 6 map area. The Boggs Table upland surface is approximately 150 feet higher in elevation than the Dry Valley floor located immediately to the east. The Wagner Creek valley floor is even lower in elevation. These numbers provide some measure of the amount of flood erosion that occurred as the massive southeast-oriented flood eroded the deep Middle Loup River valley, Mud and Clear Creek valleys, and tributary valleys headward. Note also the depression on the Boggs Table upland surface. Similar depressions are located on other upland surface remnants in this Middle Loup River-Mud Creek drainage divide area and also in what are more easily identified as flood eroded channels (see figure 10a below). Whether the Boggs Table upland depression was formed on the floor of a former flood eroded channel is difficult to say. Perhaps there is some other explanation. The upland surface remnants are too few to reconstruct flood flow channels from that data. Look at the somewhat smaller depressions in figure 10a below and make your own decision.

Spring Creek-Clear Creek drainage divide area

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

Figure 7 illustrates the Spring Creek-Clear Creek drainage divide area south and slightly east of the figure 5 map area and includes overlap areas with figure 5. Arcadia is the unnamed town located near the figure 7 east edge and is located in the valley of the southeast-oriented Middle Loup River. Spring Creek is located in the figure 7 north center area and flows southeast before turning to flow in a north-northeast direction to enter the southeast-oriented Middle Loup River as a barbed tributary. The Dry Valley seen in figures 5 and 6 above is located in the figure 7 northwest corner. Clear Creek flows in a southeast direction from the figure 7 west center edge and then in an east-northeast and southeast direction to the figure 7 south center edge. Note  northwest-oriented Moody Valley in the figure 7 southwest corner (Moody Valley will be better illustrated in figure 8 below). The north-northeast oriented Spring Creek valley and other north-oriented Middle Loup River barbed tributary valleys were eroded by reversals of flood waters on the north ends of beheaded south-oriented flood flow routes as headward erosion of the deep Middle Loup River beheaded those flood flow routes. Flood waters on the north ends of those beheaded flood flow reversed flow direction to flow north to the newly eroded and deeper Middle Loup River valley. Note the multiple through valleys linking the north-oriented Spring Creek valley with the southeast-oriented Clear Creek valley. The through valleys provide evidence of south-oriented flood flow routes that existed prior to reversal of Spring Creek drainage basin flow.  Also note northeast-oriented Lee Creek in the large northeast-oriented Lee Park valley, which drains to the southeast-oriented Middle Loup River as a barbed tributary. Further note how the northeast-oriented Lee Park valley is linked by through valleys to the southeast-oriented Clear Creek valley. In addition, note how upstream from those through valleys is a maze of southeast-oriented valleys draining the Dry Valley area to the Clear Creek valley. Probably, at one time, headward erosion of the northeast-oriented Lee Creek valley (from what was then the newly eroded Middle Loup River valley) was competing with headward erosion of the Clear Creek valley (from what was then the newly Mud Creek valley) to capture southeast-oriented flood flow moving through the Dry Valley area. Apparently considerable flood water did make the northeast jog to the Middle Loup River valley before headward erosion of the Clear Creek valley captured all of the southeast-oriented flood flow. The amount of erosion accomplished in the Lee Park region suggests the entire figure 7 map area is underlain by easily eroded material, which flood waters could easily flush from the region.

Clear Creek-Mud Creek drainage divide area

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

Figure 8 illustrates the Clear Creek-Mud Creek drainage divide area south of the figure 7 map area and includes overlap areas with figure 7. Ansley is the town located in the figure 8 southwest quadrant. Ansley is in the southeast oriented Mud Creek valley. Comer Canyon is the named south-oriented Mud Creek tributary valley north of Ansley. Clear Creek flows in an east and east-northeast direction along the figure 8 north edge (in the northwest quadrant) and then flows from the figure 8 north center edge to the figure 8 southeast corner. Note north-northwest oriented Moody Valley in the figure 8 northwest quadrant. North-northwest oriented Moody Valley was eroded by reversed flood waters on the north ends of beheaded southeast oriented flood flow routes. Evidence of the former south-oriented flood flow routes can be seen in north-south oriented through valleys linking the north-oriented Moody Valley with a headwaters of a south-oriented Mud Creek tributary, which joins Mud Creek just south of Ansley. The reversed flood flow in this case was able to erode a larger north-northwest oriented valley than the south-oriented Mud Creek tributary valley to the south. Probably this large north-northwest oriented Moody Valley was eroded by captured yet to be beheaded flood water from flood flow routes west of the Moody Valley. The Clear Creek valley eroded headward and beheaded flood flow routes or channels one channel at a time. The flood flow channels were anastomosing or interconnected, meaning reversed flow on a newly beheaded flood flow channel could easily capture yet to be beheaded flood flow from adjacent yet to be beheaded flood flow channels. Probably aiding in the erosion process was the ease with which the figure 8 map area could be eroded. While from topographic map evidence alone it is impossible to determine the nature of the figure 8 “bedrock”, all evidence seen so far in the Middle Loup River-Mud Creek drainage divide area suggests the material is easily eroded. Note also southeast and northeast oriented Ash Canyon located northeast of the figure 8 center area. Through valleys link southeast-oriented Ash Canyon headwaters with the Clear Creek valley to the north and provide evidence headward erosion of the Clear Creek valley beheaded southeast-oriented flood flow to what was then the newly eroded Ash Canyon valley. North-oriented tributary valleys provide evidence headward erosion of the northeast-oriented Ash Canyon valley segment beheaded and reversed south-oriented flood flow routes.

Brown Creek-Bloody Run Creek drainage divide area

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

Figure 9 illustrates the Brown Creek-Bloody Run Creek drainage divide area south and east of the figure 8 map area and the figure 9 northwest corner overlaps with the figure 8 southeast corner. Loup City is the town located in the figure 9 northeast corner and is located in the south-southeast oriented Middle Loup River valley. Brown Creek flows in a northeast direction from the figure 9 center area to join the south-southeast oriented Middle Loup River as a barbed tributary. North of Brown Creek is southeast and east oriented Cob Creek, which joins the Middle Loup River in the figure 9 northeast corner. Litchfield is the town located in the figure 9 southwest quadrant and is located in the southeast-oriented Mud Creek valley. The stream flowing in a south-southeast direction from the figure 9 northwest corner to join Mud Creek at the figure 9 south center edge is Clear Creek. South-southeast oriented Bloody Run Creek is located east of Clear Creek in the figure 9 south center area. Note how north of the Bloody Run Creek headwaters are northwest-oriented tributaries leading to the northeast-oriented Brown Creek and to a south-oriented Clear Creek tributary (note also how the south-oriented Clear Creek tributary is linked by a through valley with the northeast-oriented Brown Creek valley). The northwest-oriented tributary valleys to the northeast-southeast oriented valley were eroded by reversals of flood flow on the north ends of beheaded flood routes. The northeast-southwest oriented through valley may have originated as a southwest oriented valley to what was then the newly eroded Clear Creek valley and was then beheaded and reversed by headward erosion of the Middle Loup River valley. A close look at the figure 9 map area reveals many shallow through valleys crossing present day drainage divides. For example, figure 9a below illustrates a detailed map of the Clear Creek valley area seen in less detail in the figure 9 northwest quadrant. Note the presence of north-south oriented through valleys linking the north-oriented (barbed) Clear Creek tributary in sections 19 and 20 with the southeast-oriented Clear Creek tributary in sections 31 and 32. Also note a northwest-southeast oriented trough valley in the north center of section 29 linking a southeast-oriented Clear Creek tributary valley with a northeast-oriented Clear tributary valley. Other north-south oriented through valleys can be seen on either side of the Clear Creek valley (e.g. in section 29 in the figure 9a northeast quadrant). Also there are streamlined erosional residuals in the Clear Creek valley, such as those found in sections 21 and 28 (east side of Clear Creek valley).
Figure 9a: Detailed map of through valleys west of the Clear Creek valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

South end of Middle Loup River-Mud Creek drainage divide area

Figure 10: South end of Middle Loup River-Mud Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software. 

Figure 10 provides a map of the Middle Loup River-Mud Creek (and South Loup River) drainage divide south and east of the figure 9 map area and the figure 10 northwest corner overlaps with the figure 9 southeast corner. Ravenna is the town located in the figure 10 south center edge area and is located near where southeast-oriented Mud Creek joins the east-northeast and east oriented South Loup River. Sweetwater is the small town (or place-name) located in the Mud Creek valley near the figure 10 west edge (and mostly located west of the figure 10 map area). Bloody Run Creek is the south-oriented stream joining Mud Creek near Sweetwater. The Middle Loup River flows in a southeast direction from the figure 10 north center edge to join the South Loup River just east of the figure 10 southeast corner area. Rockville is the town located in the Middle Loup River valley. Dry Creek is the south-southeast oriented stream joining Mud Creek just west of Ravenna. Beaver Creek is the south-southeast oriented stream joining the South Loup River just east of Ravenna. Figure 10a below provides a more detailed map of the Middle Loup River-South Loup River drainage area east of Beaver Creek. Note how with the exception of some relatively short north-oriented barbed Middle Loup River tributaries all figure 10 drainage routes are southeast or south oriented. The Middle Loup River River-South Loup River drainage divide area east of Beaver Creek is interesting and figure 10a below provides a detailed map of that area. Note how in sections 19 and 20, section 29, and section 33 there are shallow depressions located in north-south oriented through valleys. Those north-south oriented through valleys were probably eroded by south-oriented flood waters prior to headward erosion of the deep southeast-oriented Middle Loup River valley. Flood flow in those north-south oriented through valleys was probably first captured by headward erosion of the deep east-oriented South Loup River valley and the south-oriented flood waters began to erode deeper south-oriented valleys headward from the newly eroded South Loup River north valley wall. Headward erosion of the deeper south-oriented valleys did not get very far before headward erosion of the deep southeast-oriented Middle Loup River beheaded the south-oriented flood in the three north-south oriented valleys. Today those north-south oriented through valleys provide evidence of the south-oriented flood flow channels that once crossed the entire Middle Loup River-Mud Creek drainage divide area and the depressions in those through valleys provide evidence of flood eroded depressions (and may provide an explanation for the depressions found on Boggs Table, French Tableland, and East Table).
Figure 10a: Detailed map of Middle Loup River-South Loup River drainage divide area. 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.