A geomorphic history based on topographic map evidence

The Snake Creek-North Platte River drainage divide west and south of Alliance, Nebraska was crossed by an immense southeast-oriented flood. Evidence for the flood flow is found north and west of the east-oriented Snake Creek valley and also in and along the southeast-oriented North Platte River valley. Between the Snake Creek and North Platte River valleys are what appear to be sand hills, which make topographic map interpretations of drainage history difficult if not impossible. Sand hills may have developed on flood deposited sediments. The large North Platte River valley contains erosional residuals and through valleys separating those erosional residuals, providing evidence of a flood eroded anastomosing channel complex.

• The purpose of this essay is to use topographic map interpretation methods to explore Snake Creek-North Platte River drainage divide area landform origins west and south of Alliance, 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 Snake Creek-North Platte River drainage divide area landform origins west and south of Alliance, 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.

Snake Creek-North Platte River drainage divide area location map

Figure 1: Snake Creek-North Platte 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 Snake Creek-North Platte River drainage divide area west and south of Alliance, Nebraska. Figure 1 illustrates the Nebraska Panhandle area with South Dakota located north of Nebraska, Wyoming west of the Nebraska Panhandle, and Colorado south of the Nebraska Panhandle. The North Platte River flows in a southeast direction from the figure 1 west center edge to Scottsbluff, Nebraska and then to Bridgeport, Oshkosh, and North Platte, where it joins the South Platte River to form the southeast-oriented Platte River, which flows to the figure 1 southeast corner. The South Platte River flows in a northeast direction from Sterling, Colorado to the Colorado northeast corner and to Ogallala, Nebraska before joining the North Platte River at North Platte, Nebraska. The Niobrara River flows in a southeast direction in the figure 1 northwest quadrant from Van Tassel, Wyoming to the Agate Fossil Beds National Monument and then east to Box Butte Reservoir before turning to flow in a northeast direction to near the Nebraska-South Dakota state line, where it then flows in an east direction to Valentine and the figure 1 east edge. Snake Creek is the unlabeled stream on figure 1 originating between the Agate Fossil Beds National Monument and Scottsbuff and flowing in a southeast and east direction to Alliance. Snake Creek ceases to exist as a surface stream near the Alliance airport. This essay addresses the drainage divide region between Snake Creek (where it exists as a surface stream) and the North Platte River. Note the large Nebraska Sand Hills region immediately east of Alliance. Surface drainage routes in the eastern Sand Hills region are generally east-oriented. Northern Sand Hills area streams turn to flow to the Niobrara River while further south the east-oriented drainage routes turn to flow southeast as Loup River tributaries, with water eventually reaching the Platte River. The Snake Creek-North Platte River drainage divide area south and east Alliance essay addresses the region located east of this essay’s study region, and the eastern Wyoming and western Nebraska Niobrara River-North Platte River drainage divide area essay addresses the region located west of this essay’s study region.  The Niobrara River-Snake Creek drainage divide area essay addresses the region located north of this essay’s study area. Essays can be found under appropriate river names on the sidebar category list. Hundreds of Missouri River drainage basin landform origins research project essays published on this website document significant evidence for an immense southeast-oriented flood, which flowed from regions northwest of the figure 1 map area into western Nebraska. The Nebraska Sand Hills region is interpreted to have probably originated as sandy deltas formed where flood waters entered temporary lakes formed by the convergence of flood waters, which had used different routes to reach Nebraska. Flood waters were drained from the region by headward erosion of present day valleys, with the Platte River-North Platte River valley eroding headward prior to headward erosion of the Niobrara River valley to the north. Headward erosion of the Niobrara River valley beheaded all western Nebraska flood flow routes to the North Platte River valley. Subsequently eolian activity developed sand hills and obscured most flood eroded valleys in the Sand Hills region.

Snake Creek-North Platte River drainage divide area detailed location map

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

Figure 2 provides a somewhat more detailed location map for the Snake Creek-North Platte River drainage divide area west and south of Alliance, Nebraska. Sioux, Box Butte, Scotts Bluff and Morrill are Nebraska County names and the county boundaries are shown. Goshen County, Wyoming is located west of Sioux and Scotts Bluff Counties, Nebraska. The North Platte River flows from the figure 2 west center edge to the Scotts Bluff County northwest corner and then into Morrill County before reaching the figure 2 south edge (east half). The Niobrara River flows in a southeast direction from the figure 2 north edge (west half) to Agate Fossil Beds National Monument (in Sioux County) and then east along the Box Butte County north border before turning to flow in a northeast direction to the figure 2 northeast corner. The North and South Branches of Snake Creek flow in a southeast direction in the Sioux County southeast corner and join in the Box Butte County southwest corner. Snake Creek then flows across southern Box Butte County to the Alliance airport area (located southeast of Alliance) and then disappears as a surface stream. Note the numerous southeast-oriented Niobrara River tributaries near the figure 2 north edge and the numerous southeast-oriented Snake Creek tributaries in Box Butte County. These southeast-oriented tributaries are evidence the Snake Creek valley and the Niobrara River valley eroded headward to capture multiple southeast-oriented flood flow channels, such as might be found in a southeast-oriented anastomosing channel complex. Headward erosion of the Snake Creek valley captured the flood water first and headward erosion of the Niobrara River valley captured the southeast-oriented flood water next and beheaded flood flow routes to the newly eroded Snake Creek valley. Prior to Snake Creek valley headward erosion flood waters were moving to what was then the newly eroded North Platte River valley. And prior to North Platte River valley headward erosion flood waters were moving further southeast to what were then the newly eroded east-oriented valleys south of figure 2. Headward erosion of the North Platte River valley captured significant southeast-oriented flood flow in Wyoming and those flood waters moved across the figure 2 map area in what is today the rather large southeast-oriented North Platte River valley. Sand hills obscure much of the drainage history evidence between the Snake Creek valley and the North Platte River valley, although evidence for flood erosion is excellent in the North Platte River valley.

Snake Creek-North Platte River drainage divide area north of Scottsbluff

Figure 3: Snake Creek-North Platte River drainage divide area north of Scottsbluff. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 uses reduced size maps to illustrate the Snake Creek-North Platte River drainage divide area north and east of Scottsbluff. The southeast-oriented North Platte River flows across the figure 3 southwest corner. Scottsbluff is the city located along the figure 3 south edge (west half). Snake Creek is located in the figure 3 northeast quadrant, with the North and South Branches flowing in a southeast direction from the figure 3 north edge to combine and flow in a southeast direction to Kilpatrick Reservoir and then to the figure 3 east edge. Mud Springs Creek originates in the figure 3 north center area and flows in an east direction near the figure 3 north edge to join the southeast-oriented South Branch Snake Creek. Spring Creek flows in a north direction (from south of Kilpatrick Reservoir) and then turns to flow in an east direction to join Snake Creek downstream from the Kilpatrick Reservoir dam (on the map a Spring Creek segment parallel to Snake Creek is labeled as a canal). Figure 3a below provides a more detailed map of the area where the South and North Branches of Snake Creek meet. Notice on figure 3a the northwest-southeast oriented erosional residuals and valleys or channels separating those erosional residuals. The erosional residuals and through valleys provide evidence of a southeast-oriented anastomosing channel complex, which is evidence of a flood eroded topography. Southeast-oriented flood waters were apparently captured by headward erosion of the Snake Creek valley, which eroded headward from somewhere east of Alliance (today the Snake Creek valley east of Alliance is obscured by sand hills). Referring back to figure 3 note the size of the southeast-oriented North Platte River valley in comparison with the Snake Creek valley to the north. Also note the presence of erosional residuals in the North Platte River valley, just as there are erosional residuals in the Snake Creek drainage basin to the northeast. Lake Alice and Lake Minatare are irrigation system reservoirs and irrigation canals make use of through valleys along the North Platte River valley north wall. Figure 7 below illustrates the North Platte River valley in slightly more detail so as to better show evidence for flood eroded anastomosing channels.

Figure 3a: Detailed map of the region where South and North Branches of Snake Creek join. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Snake Creek-North Platte River drainage divide area southwest of Alliance

Figure 4: Snake Creek-North Platte River drainage divide area southwest of Alliance. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 uses reduced size maps to illustrate the Snake Creek-North Platte River drainage divide area west and south of Alliance and is located east and north of the figure 3 map area and includes overlap areas with figure 3. Alliance is the city located along the figure 4 east edge (north half). The South and North Branches of Snake Creek flow in southeast directions from the figure 4 northwest corner to join and then flow as Snake Creek to Kilpatrick Reservoir. From Kilpatrick Reservoir Snake Creek flows in an east direction to the figure 4 east edge (south of Alliance) and disappears in the sand hills located east of the figure 4 map area. Note the southeast-oriented Snake Creek tributaries in the region north of the east oriented Snake Creek segment. These southeast-oriented tributaries provide evidence Snake Creek valley headward erosion captured multiple southeast-oriented flood flow channels, which were moving a large southeast-oriented flood to what was then the newly eroded North Platte River valley. South of the east oriented Snake Creek segment there is a rather sharp change in the nature of the landscape, which corresponds with the county line. Some of the landscape difference relates to different maps which were joined along that line and has nothing to do with the actual topography. However, some of the landscape change is due to the presence of what appear to be low sand hills in the Snake Creek-North Platte River drainage divide area. The sand hills have obscured whatever water eroded landforms once existed in that drainage divide area. The sand hills are probably developed on flood deposited deltas, formed where flood waters entered large standing bodies of water. Such large standing bodies of water may have existed in the region east of the figure 4 map area because the massive southeast-oriented floods from the northwest (and which other essays can be used to trace headward into north central Montana) converged in western and central Nebraska with massive east- and northeast-oriented floods from Wyoming and Colorado (those flood routes through the Rocky Mountains are documented other essays). Floods were probably derived from the same rapidly melting North American ice sheet, however the floods used very different routes to reach Nebraska. Because sand hills probably obscure flood eroded valleys across the present day Snake Creek-North Platte River drainage divide area figures below illustrate and discuss evidence in and adjacent to the North Platte River valley, where topographic map drainage route evidence can be seen.

Dry Sheep Creek-Spottedtail Creek drainage divide area

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

Figure 5 illustrates the Dry Sheep Creek-Spotted Tail Creek drainage divide area north of the North Platte River and is located west of the figure 3 map area and includes overlap areas with figure 3. The southeast-oriented North Platte River is located in the figure 5 southwest corner. Except for a small region in the figure 5 northeast corner the figure 5 map area illustrates a North Platte River valley region. Morrill is the town the figure 5 southwest quadrant and Mitchell is the town located along the figure 5 south center edge. Dry Sheep Creek is the south, southwest, south, and southeast oriented stream in the figure 5 west half flowing from the north edge to Morrill. Dry Spottedtail Creek flows south from the figure 5 north edge to Mitchell in the figure 5 center. East of Dry Spottedtail Creek is south-southwest oriented Spottedtail Creek, which also flows from the figure 5 north edge (east half) to Mitchell. In the figure 5 northeast quadrant Wind Springs Creek flows in a south-southwest direction near the figure 5 east edge. The area marked The Horseshoe in the figure 5 northeast quadrant is shown in more detail in figure 6 below. Figure 6 evidence reveals multiple northwest-southeast oriented through valleys linking the Dry Sheep Creek valley with the Dry Spottedtail Creek and Spottedtail Creek valleys and with south-oriented North Platte River tributary valleys further to the east and southeast. For example, just west of the highway near the figure 5 north center edge is a fairly deep through valley. That through valley was eroded by southeast-oriented flood water at the same time the large North Platte River valley was eroded. Note also how the irrigation canal from the Dry Spottedtail Creek valley in the figure 5 north center area to the figure 5 east edge makes use of through valleys further to the southeast. The through valleys and erosional residuals located between those through valleys provide evidence southeast-oriented flood waters eroding the North Platte River valley carved multiple channels, such as might be found in an anastomosing channel complex. Through valleys can not be eroded unless flood water flows simultaneously in multiple valleys which means the figure 5 map area was crossed by anastomosing flood channels.

Detailed map of The Horseshoe escarpment area

Figure 6: Detailed map of The Horseshoe escarpment area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 provides a detailed map of The Horseshoe region seen in less detail in figure 5 above. The Horseshoe is an escarpment surrounding a west-oriented basin, which drains to a south oriented valley. South-southwest oriented Spottedtail Creek can be seen in the figure 6 northwest corner and is located just west of the figure 6 west edge further to the south. Drainage in the Horseshoe basin (at least before the irrigation canal was constructed) flowed to Spottedtail Creek and then south to the North Platte River. The Horseshoe evidence permits drainage history reconstruction. In the section 8 northeast quadrant (in figure 6 center southeast area) there is a northwest-southeast oriented through valley linking a northwest-oriented stream flowing to the Horseshoe basin with a southeast-oriented stream flowing to the unnamed south oriented North Platte River tributary located in the figure 6 southeast quadrant. Further, while the Horseshoe appears to be a west-oriented basin, water flowing into the Horseshoe basin appears to have come from the northwest. Note the shallow northwest-southeast oriented through valley in the section 5 northeast corner and how that through valley links northwest-oriented headwaters of a Spottedtail Creek tributary with southeast oriented headwaters of what rapidly becomes a south and west oriented valley. Also note a similar shallow northwest-southeast oriented through valley in the section 4 northwest corner linking headwaters of northwest oriented Spottedtail Creek tributaries with southeast oriented headwaters of the south-oriented unnamed North Platte River tributary flowing to the figure 6 southeast quadrant. These through valleys and orientations of the tributary valleys suggest the figure 6 map area was eroded by southeast oriented flood water, which initially flowed across the entire figure 6 map area on a topographic surface at least as high as the highest figure 6 elevations today. Headward erosion of the deep North Platte River valley significantly lowered base level in the south and east of the figure 6 map area. Headward erosion of the unnamed tributary flowing south through the figure 6 southeast quadrant occurred first and captured southeast oriented flood flow north of the newly eroded North Platte River valley. Next headward erosion of a south-southwest oriented Spottedtail Creek tributary valley eroded headward into the Horseshoe basin area and beheaded some (but not all of the southeast-oriented flood flow routes to the newly eroded south oriented valley east of the Horseshoe. A south-oriented valley then eroded headward into section 6 northeast of Rattlesnake Hill and captured many, but not all of the southeast oriented flood flow routes to the newly eroded eastern Horseshoe basin (through valleys across the drainage divide north of Rattlesnake Hill are evidence southeast oriented flood flow moved across that drainage divide into the Horseshoe basin). Next headward erosion of the Spottedtail Creek valley beheaded all southeast oriented flood flow to the Horseshoe basin and to the unnamed south oriented valley east of the Horseshoe.

Spottedtail Creek-Winters Creek drainage divide area

Figure 7 illustrates the Spottedtail Creek-Winters Creek drainage divide area north of Scottsbluff, east and south of the figure 5 map area, and including overlap areas with figure 5. Mitchell is the town located on the figure 7 west center edge. Scottsbluff is the city located near the figure 7 south center edge. The North Platte River flows in a southeast direction from Mitchell to Scottsbluff. Spottedtail Creek flows in a south-southwest direction in the figure 7 northwest corner area. Winters Creek flows in a south-southwest direction from the figure 7 north edge (east half) to Winters Creek Lake and then in a southwest direction to Scottsbluff. Lakes in the figure 7 map area, which are Lake Alice, Lake Alice No. 2, Winters Creek Lake, and Lake Minatare, are reservoirs used in the regional irrigation system. Note how irrigation canals make use of through valleys along the North Platte River valley’s northeast wall and other through valleys between erosional residuals. The through valleys and erosional residuals provide evidence of multiple southeast and south oriented flood flow routes, such as might be found where a south-southeast and/or south oriented anastomosing channel complex is entering a southeast-oriented flood eroded valley and/or anastomosing channel complex area. At one time flood waters were moving in all of the figure 7 channels simultaneously. While south-oriented valleys eroded headward in sequence from east to west, the southeast-oriented channels downstream from those south-oriented valleys were all filled with water as the figure 7 map area landscape was eroded. Southeast-oriented valleys eroded headward from the newly eroded west walls of the south-oriented valleys. Flood waters were flowing in all of what are today valleys between the erosional residuals. Without such an explanation the figure 7 landscape is almost impossible to explain. What has happened here is southeast-oriented flood waters were flowing across the entire figure 7 map area on a topographic at least as high as the highest figure 7 elevations today. Headward erosion of the deep southeast-oriented North Platte River valley then entered the region and south-oriented tributary valleys eroded north and northeast in sequence (from the east to the west) to capture southeast-oriented flood flow routes north and east of what was initially a much narrower North Platte River valley. Captured flood flow routes closest to the North Platte River valley began to erode deep southeast-oriented valleys headward from the newly eroded south- and/or southwest-oriented North Platte River tributary valleys. This process was repeated over and over again across the figure 7 map area.

Red Willow Creek-Upper Dugout Creek drainage divide area

Figure 8 illustrates the Red Willow Creek-Upper Dugout Creek  drainage divide east and south of the figure 7 map area and does not include overlap areas with figure 7. The southeast oriented North Platte River is located in the figure 8 south half and flows from the figure 8 west edge to Bridgeport, which is the town located along the figure 8 south edge (east half). Northport is the smaller town across the river from Bridgeport. Bayard is the town located in the figure 8 west center edge area and north of the North Platte River. The upland surface located northeast of the North Platte River valley can be seen in the figure 8 northeast quadrant. Wildhorse Drain is a south-oriented canal draining to Bayard from the figure 8 northwest corner. East of Wildhorse Drain is Wildhorse Canyon, which may or may not represent the original stream route (north of figure 8 Wildhorse Canyon is a short southeast and south oriented canyon eroded into the North Platte River valley north wall). East of Wildhorse Canyon and near the figure 8 north center Red Willow Creek flows in a south-southwest direction from the figure 8 north edge and then turns to flow south toward the North Platte River. West Water Creek is the southeast-oriented Red Willow Creek tributary seen near the figure 8 north edge. Further east, originating east of the highway is south-southwest and south-southeast oriented Indian Creek, which flows to the North Platte River just west of Northport. Note how the railroad follows the Indian Creek valley as it descends from the upland surface into the North Platte River valley. The Indian Creek valley is shown in more detail in figure 9 below. East of Indian Creek is south-southwest oriented Upper Dugout Creek, which flows to the North Platte River at Northport. Bratten Creek is a southwest-oriented Upper Dugout Creek tributary. In the North Platte River valley there are more erosional residuals providing evidence of southeast-oriented valleys eroding headward from newly eroded south-oriented tributary valleys to the what was then the newly eroded, deep, and much narrower North Platte River valley. Figure 10 below provides a more detailed map of erosional residuals between the southeast-oriented Indian Creek and south-southwest oriented Upper Dugout Creek channels. A very close look at figure 10 evidence (or better yet at more detailed topographic maps) reveals the south and south-southwest oriented North Platte River tributaries, where they have eroded headward into the northeast valley wall, are linked by shallow northwest-southeast through valleys. Figures 9 illustrates evidence the Indian Creek valley captured southeast-oriented flood flow.

Detailed map of Indian Creek headwaters area

Figure 9 provides a detailed map of the Indian Creek headwaters area seen in less detail in figure 8 above. Indian Creek is the southwest-oriented stream in the figure 9 southeast quadrant. Note how Indian Creek has south-oriented tributaries flowing through sections 33, 4, and 9 and also in sections 5 and 8. Also note how the tributary in sections 4 and 9 has southeast-oriented tributaries. The red highway, which extends in a south-southwest direction from the figure 9 north edge to the figure 9 south edge is located on a high drainage divide between the Red Willow Creek drainage basin to the west and the Indian Creek drainage basin to the east. Note how that drainage divide is crossed by several shallow northwest-southeast oriented through valleys (the valleys are usually only one contour line deep). While these valleys may appear to be insignificant they link south-oriented Indian Creek tributary valleys with northwest and west oriented headwaters of Red Willow Creek tributaries and provide evidence the Indian Creek valley eroded headward (to the northeast) to capture multiple southeast-oriented flood flow routes located on the upland surface adjacent to what was then the newly eroded southeast-oriented North Platte River valley. At that time the Red Willow Creek valley and drainage basin did not exist, although headward erosion of the Red Willow Creek valley and its tributary valleys occurred shortly after headward erosion of the Indian Creek valley and its tributary valley. The northwest- and west-oriented Red Willow Creek tributary valleys were eroded by reversals of flood flow on the northwest and west ends of beheaded flood flow routes. Remember, headward erosion of the Red Willow Creek valley (like headward erosion of any valley) beheaded flood flow routes one channel at a time. Also remember, the southeast-oriented flood flow routes were anastomosing or interconnected, which meant reversed flow on one channel could capture yet to be beheaded flood flow from adjacent flood flow channels. Captures of yet to be beheaded flood flow played a significant role in eroding the Red Willow Creek tributary valleys. Note also where the railroad crosses the drainage divide between the south-southwest oriented Indian Creek tributary in section 4 and southwest-oriented Indian Creek in sections 5 and 10. The railroad makes use of a shallow northwest-southeast oriented through valley eroded across that drainage divide. Other less obvious through valleys also cross that drainage divide. Combined the through valleys provide evidence the Indian Creek valley in sections 4 and 9 eroded headward to capture southeast-oriented flood flow channels moving flood waters to what was then the newly eroded Indian Creek valley. The evidence is subtle, but the  through valleys and southeast-northwest tributary and headwaters orientations are evidence of southeast-oriented flood flow.

Detailed map of Indian Creek-Upper Dugout Creek drainage divide area

Figure 10: Detailed map of Indian Creek-Upper Dugout Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 10 provides a detailed map of the Indian Creek-Upper Dugout Creek drainage divide area seen is less detail in figure 8 and located south of the figure 9 map area. The southeast oriented North Platte River is located in the figure 10 southwest quadrant. Northport is the town located where the North Platte River crosses the figure 10 south center edge. Indian Creek flows in a southeast direction from the figure 10 northwest corner to join the North Platte River west of Northport. Upper Dugout Creek flows in a southwest and south direction from the figure 10 northeast quadrant to join the North Platte River at Northport. Indian Creek, which in figure 9 was southwest oriented, has made a significant turn as it entered the North Platte River valley to flow in a southeast direction (see figure 8). Note how Indian Creek flows between northwest-southeast oriented erosional residuals and also the large through valley at Kemp (on the railroad at the boundary between sections 8 and 17) linking the southeast oriented Indian Creek valley with the south-oriented Upper Dugout Creek valley. What has happened here is prior to North Platte River valley headward erosion southeast-oriented flood flow moved across the entire figure 10 map area on a topographic surface at least as high as the highest figure 9 and 10 elevations today. Headward erosion of the deep southeast-oriented North Platte River valley captured the southeast -oriented flood flow and tributary valleys eroded north and northwest from the newly eroded North Platte River valley to capture adjacent southeast-oriented flood flow channels. One such tributary valley eroded north and northwest from the Northport area (east of the erosional residual in sections 17 and 20) and then west in the Kemp area along southeast-oriented flood flow routes. At approximately the same time another tributary valley eroded northwest along the present day Indian Creek alignment and beheaded east-oriented flood flow to the newly eroded valley in the Kemp area. Headward erosion of another tributary valley west of the Indian Creek valley next produced the erosion residual in the figure 10 west center edge area. Bricker Lakes in section 22 in the figure 10 southeast quadrant are located in a northwest-oriented basin, which is linked by through valleys at the southeast end to the North Platte River valley south of the figure 10 map area. The northwest-oriented basin suggests considerable reversed flow occurred when what was a southeast-oriented flood flow channel was beheaded by headward erosion of south-oriented Upper Dugout Creek valley. Also supporting the southeast-oriented flood flow interpretation is the deep through valley crossing the drainage divide in the section 23 northeast corner (in the figure 10 southeast quadrant).

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.