Frenchman Creek-Rock Creek drainage divide area landform origins, western Valley and eastern Phillips Counties, Montana, USA

· Frenchman River, Milk River, Montana
Authors

Abstract:

Topographic map evidence is used to interpret landform origins in the Frenchman River-Rock Creek drainage divide area in western Valley and eastern Phillips Counties, Montana. The Frenchman River and Rock Creek originate in southern Saskatchewan and after entering Montana flow in generally south directions to join the southeast-oriented Milk River. Rock Creek is located east of the Frenchman River. The Frenchman River-Rock Creek drainage divide south of the Canadian border is an asymmetric drainage divide with south-southeast oriented Rock Creek tributaries from the west being longer than the relatively few Frenchman River tributaries from the east. Northwest-oriented barbed tributaries and/or valley segments can be found throughout the region and are usually linked by through valleys to south-southeast oriented valleys further the south. Topographic map evidence suggests massive south-southeast oriented floods crossed the entire Frenchman River-Rock Creek drainage divide area as the south-oriented Rock Creek valley eroded headward from what was probably an actively eroding southeast-oriented Milk River valley to capture multiple south-southeast oriented flood flow channels, such as might be found in a large south-southeast-oriented anastomosing channel complex. Headward erosion of the south-oriented Frenchman River valley next beheaded the south-southeast oriented flood flow channels to the newly eroded Rock Creek valley, with flood waters on north-northwest ends of the beheaded flood flow channels reversing flow direction to erode the northwest-oriented tributary valleys and valley segments. Flood waters were probably derived from a rapidly melting North American ice sheet and were flowing along the ice sheet’s southwest margin.

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 Frenchman River-Rock Creek drainage divide area landform origins in western Valley and eastern Phillips Counties, Montana, 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 Frenchman River-Rock Creek drainage divide area landform evidence in western Valley and eastern Phillips Counties, Montana 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.

Frenchman River-Rock Creek drainage divide area location map

Figure 1: Frenchman River-Rock 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 is a location map for the Frenchman River-Rock Creek drainage divide area located in western Valley and eastern Phillips Counties, Montana and illustrates a region in northern Montana with southern Saskatchewan located north of the international border. The Missouri River flows in an east direction from the figure 1 west edge (just north of southwest corner) to Fort Peck Reservoir and then flows in an east direction from Fort Peck Dam to Wolf Point, Montana and to the figure 1 east edge. The Milk River flows from the figure 1 west edge (south of the international border) to Chinook, Harlem, Malta, Hinsdale, and Glasgow, Montana before joining the Missouri River a short distance downstream from Fort Peck Dam. The Frenchman River flows in an east and east-southeast direction from the figure 1 west edge (north of international border) to Eastend and Val Marie, Saskatchewan before crossing the international border at Grasslands National Park (west section) and turning to flow in a south direction to join the Milk River near Saco, Montana. Rock Creek is located east of the Frenchman River and originates in the Wood Mountain area, just north of the international border, and flows in a south-southwest and south direction to join the Milk River near Hinsdale, Montana. West of the Frenchman River is southeast-oriented Whitewater Creek and east of Rock Creek is south-oriented Porcupine Creek. The Frenchman River-Rock Creek drainage divide area investigated in this essay is located south of the international border, north of the Milk River, east of the Frenchman River, and west of Rock Creek. Other nearby drainage divides addressed by other essays include the Wood River-Frenchman River drainage divide and the Wood River-Poplar River drainage divide area landform origins north of the international border and the Rock Creek-Porcupine Creek drainage divide area east of Rock Creek. These and other Milk River drainage divide areas can be found under Milk River on the sidebar category list.
  • Based on topographic map evidence presented in this essay and in hundreds of similar Missouri River drainage basin drainage landform origins research project essays the Frenchman River-Rock Creek drainage divide area was eroded by massive southeast and south-oriented oriented glacial melt water floods, which flowed across the entire figure 1 map area. Flood waters were derived from a rapidly melting thick North American ice sheet and were flowing along the ice sheet’s southwest margin, which had been detached by a giant southeast and south oriented ice-walled and bedrock-floored canyon. The ice-walled and bedrock-floored canyon had been carved into the decaying ice sheet surface by an immense southeast- and south-oriented supra glacial melt water river, which emerged from the ice sheet margin in southeast South Dakota. The ice sheet had formed on a topographic surface now preserved, if it is preserved at all, on the highest level Rocky Mountain erosion surfaces and had formed a deep “hole” in the North American continent. The deep “hole” had been formed by deep glacial erosion (underneath the massive ice sheet) and by crustal warping caused by ice sheet’s great weight. Late during the ice sheet melt down history supra glacial rivers carved large ice-walled canyons into the decaying ice sheet’s surface and floors of these ice-walled canyons were significantly lower than elevations of ice marginal regions, especially in the figure 1 map area. While a massive northwest-southeast oriented ice barrier stood between the higher ice-marginal melt water floods in the figure 1 map area and the ice-walled and bedrock-floored canyon floor (to the northeast of the figure 1 map area) breaches through the decaying ice barrier did open up and deep northeast and east-oriented valleys eroded rapidly headward to capture the immense southeast-oriented ice-marginal floods. The Missouri River valley  and tributary valleys including the Milk River, Rock Creek, and Frenchman River valleys (as seen in figure 1) eroded headward from an ice barrier breach near the Montana northeast corner and North Dakota northwest corner. At that time the valleys were much deeper than they appear today and the massive melt water floods significantly lowered the regional surface as the deep valleys eroded headward across the figure 1 map area.
  • Note: United States maps used in this essay use the name Frenchman Creek, although Canadian maps use the name Frenchman River. I am using the name Frenchman River on both sides of the international border to be consistent and because most of the drainage route is in Canada.

Detailed location map for Frenchman River-Rock Creek drainage divide area

Figure 2: Detailed location map for Frenchman River-Rock Creek drainage divide area.United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 2 provides a detailed location map for the Frenchman River-Rock Creek drainage divide area in western Valley and eastern Phillips Counties, Montana. The Canada-United States border is located along the figure 2 north edge. Valley County is located in the figure 2 east half, Phillips County is located in the west half, and the county boundary line is shown. The Milk River flows in a north-northeast direction from the figure 2 west edge (just north of the southwest corner) and then turns to flow in a southeast direction so as to flow  north of Hewitt Lake National Wildlife Refuge and Nelson Reservoir before flowing to the figure 2 south center edge. Beaver Creek is the northeast and southeast-oriented stream south of the Milk River in the figure 2 southwest quadrant, which flows through Saco and Beaverton before joining the Milk River near Hinsdale (near figure 2 south center edge). Rock Creek flows in a south-southwest and south direction in western Valley County from the figure 2 north edge (east of center) to join the Milk River near Hinsdale. The Frenchman River flows in a south-southeast and south direction just west of the county boundary to join the Milk River along near the county line slightly north of Beaverton. Note how the Frenchman River-Rock Creek drainage divide area is drained primarily by south-southeast oriented Rock Creek tributaries. Named Rock Creek tributaries from north to south are Bluff Creek, Crow Creek, Big Snake Creek, and Cash Creek (Cache Creek on more detailed maps) and their tributaries. Other than two unnamed south-oriented tributaries near the Canadian border figure 2 shows no Frenchman River tributaries from the east, although numerous unnamed south-southeast oriented tributaries are shown joining Frenchman Creek from the west. This arrangement of tributaries suggests the south-oriented Rock Creek valley captured multiple south-southeast oriented flood flow channels such as might be found in a south-southeast oriented anastomosing channel complex as it eroded headward. Next the south-oriented Frenchman River valley eroded headward across the same south-southeast oriented flood flow channels and beheaded flood flow channels moving water to the newly eroded Rock Creek valley. Rock Creek tributaries from the east are generally oriented in southwest directions, although evidence presented in the Rock Creek-Porcupine Creek drainage divide area landform origins essay suggests those southwest-oriented tributary valleys were eroded headward across south-southeast oriented flood flow channels leading to the south-oriented Porcupine Creek valley.

South End of Frenchman River-Rock drainage divide area

Figure 3: South end of Frenchman River-Rock Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 3 illustrates the south end of the Frenchman River-Rock Creek drainage divide area and will serve as a the starting point for this essay. The Milk River flows in an east and southeast direction from the figure 3 west edge (just north of southwest corner) to the south edge (just west of center). The Frenchman River flows in a southwest and south direction from the figure 3 north edge (just east of northwest corner) to join the Milk River near the figure 3 southwest corner. Rock Creek flows in a south direction from the figure 3 north edge to the south edge (both near figure 3 east edge) and joins the southeast-oriented Milk River south of the figure 3 map area. Major Rock Creek tributaries from the west are all oriented in south-southeast directions and include Cache Creek, Papoose Creek, and their tributaries. Cache Creek tributaries include Turnip Coulee, Bell Coulee, Brush Coulee, and East, Middle, and West Forks. Papoose Creek tributaries from the west include Norwegian Coulee and Sheepherders Coulee and from the east Jones Coulee and Hay Coulee. Note how these tributaries are all oriented in southeast, south-southeast, or south directions. Note also how the Milk River has almost no south-oriented tributaries in the region between the Frenchman River and Rock Creek. The one exception is relatively short Swanson Coulee located near the north-south oriented Phillips-Valley County line. Also, only one Frenchman River tributary from the east is shown and that is south, northwest, and southwest oriented Anderson Coulee. Note how the northwest-oriented Anderson Coulee segment is on the same alignment as southeast-oriented Bell Coulee. This drainage pattern suggests the south-oriented Rock Creek valley eroded headward across multiple south-southeast oriented flood flow channels, such as might be found in a south-southeast oriented anastomosing channel complex. Headward erosion of the south-oriented Frenchman River valley next beheaded the south-southeast oriented flood flow channels in sequence from south to north. The northwest-oriented Swanson Coulee valley segment was eroded by a reversal of flood flow on the northwest end of a southeast-oriented flood flow channel, which was beheaded by headward erosion of the southwest-oriented Swanson Coulee valley.

Detailed map of Bull Pasture Coulee-Jones Coulee drainage divide area

Figure 4: Detailed map of Bull Pasture Coulee-Jones Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 4 illustrates a detailed topographic map of the Bull Pasture Coulee-Jones Coulee drainage divide area located just north of the figure 3 northeast quadrant (see figure 5 for region directly north of figure 3). Rock Creek makes a jog to the southeast in the figure 4 northeast corner region and then flows in a south direction along the figure 4 east edge. Bull Pasture Coulee drains in a northeast direction in the figure 4 northeast quadrant to join the southeast-oriented Rock Creek segment. The south-oriented stream near the figure 4 west edge is the East Fork Cache Creek, which flows from the figure 4 north edge to the south edge with a jog to the northwest in the figure 4 northwest quadrant. East of East Fork Cache Creek is south, southwest, and south-southeast oriented Papoose Creek, which also flows from the north edge (west of center) to the south edge (also west of center). Note how in the figure 4 northwest quadrant the East Fork Cache Creek and Papoose Creek valleys are linked by through valleys, which cross the drainage divide. The northwest-oriented East Fork Cache Creek valley segment for example is linked to a south-southeast oriented tributary valley from the north and to a south-southeast oriented through valley to the south-southeast oriented Papoose Creek valley. The through valley and the East Fork Cache Creek northwest jog provide evidence of a south-southeast oriented flood flow channel beheaded and reversed by East Fork Cache Creek valley headward erosion. The south-oriented valley near the west borders of sections 17 and 20 in the figure 4 southeast quadrant is Jones Coulee, which drains to south-southeast oriented Papoose Creek south of the figure 4 map area. Note how the south-oriented Jones Coulee valley is linked by a north-south oriented through valley with a north-oriented Bull Pasture Coulee tributary valley. The map contour interval is 20 feet and the through valley floor elevation at the drainage divide is between 2660 and 2680 feet (probably closer to 2680 feet). Elevations on the hill to the west rise to more than 2840 feet while a hill to the east has an elevation greater than 2780 feet. In other words the through valley is at least 100 feet deep. The through valley provides evidence of a south-oriented flood flow channel to what was once the actively eroding Papoose Creek valley prior to headward erosion of the northeast-oriented Bull Pasture Coulee valley. Bull Pasture Coulee valley headward erosion was probably initiated by a reversal of flood flow on the north end of the south-oriented flood flow channel beheaded by headward erosion of the southeast-oriented Rock Creek valley segment. Other similar flood flow channel reconstructions can be made from similar topographic map evidence.

Panhandle Coulee-Cache Creek drainage divide area

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

 

Figure 5 illustrates the Panhandle Coulee-Cache Creek drainage divide area north of the figure 3 map area and includes overlap areas with figure 3. The Frenchman River flows in a south direction near the figure 5 west edge. Rock Creek flows in a south-southeast direction in the figure 5 east half from the north edge through Rock Creek Canyon and then turns to flow in a south direction to the figure 5 south edge (second stream from southeast corner). The East Fork Cache Creek flows in a south direction from the figure 5 center region to the figure 5 south center edge. The south-southeast oriented Middle and West Forks of Cache Creek are located west of the East Fork Cache Creek and combine south of figure 5 to form south-southeast oriented Cache Creek, which is a Rock Creek tributary. The south-southeast oriented stream flowing along the east side of Windy Ridge (just east of the East Fork Cache Creek) is Papoose Creek, which is also a Rock Creek tributary. South-oriented Jones Coulee is located between Papoose Creek and Rock Creek and northeast-oriented Bull Pasture Coulee is located just north of the Jones Coulee headwaters. Panhandle Coulee is a northwest and southwest-oriented drainage route in the figure 5 northwest quadrant draining to the Frenchman River valley just downstream from Frenchman Reservoir. East of northwest-oriented Panhandle Coulee is northwest-oriented Jordan Coulee, which north of the figure 5 map area turns in an east direction to join east and east-southeast oriented Rock Creek tributaries. The northwest-oriented Panhandle Coulee and Jordan Coulee valleys were eroded by reversals of flood flow on northwest ends of beheaded south-southeast oriented flood flow channels. Note how north of Windy Ridge the East Fork Cache Creek valley is linked by shallow through valleys with north-northwest oriented valleys draining to Panhandle Coulee and Jordan Coulee. These through valleys provide evidence of former south-southeast oriented flood flow channels. The north-northwest and south-southeast orientation of drainage routes in the present day Frenchman River-Rock Creek drainage divide area, combined with the through valleys, again provides evidence Rock Creek valley headward erosion captured multiple south-southeast oriented flood flow channels and then headward erosion of the Frenchman River valley and its southwest-oriented tributary valleys beheaded those flood flow channels and reversed flood flow on the northwest ends of the beheaded flood flow routes.

Detailed map of Jordan Coulee-East Fork Cache Creek drainage divide area

Figure 6: Detailed map of Jordan Coulee-East Fork Cache Creek drainage divide area.United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 6 provides a detailed topographic map of the Jordan Coulee-East Fork Cache Creek drainage divide area and also of the Panhandle Coulee-East Fork Cache Creek drainage divide area seen in less detail in figure 5 above. The East Fork Cache Creek flows in a south, northwest, and south direction in the figure 6 southeast quadrant. South-oriented streams flowing to the figure 6 south center edge are East Fork Cache Creek tributaries. The south-oriented stream located west of the south center edge is the headwaters of the Middle Fork Cache Creek. Jordan Coulee is the north-northwest and north oriented stream in the figure 6 northeast quadrant (and is labeled by the word “Coulee”). North of the figure 6 map area Jordan Coulee turns to flow in an east direction to join Little Snake Creek, which then joins Big Snake Creek, which flows to Rock Creek (see figure 7). Panhandle Coulee drains in a north-northwest direction from the figure 6 center region to the north edge (west of center) and north of the figure 6 map area turns to flow in a southwest direction across the figure 6 northwest corner. Note how the southwest-oriented Panhandle Coulee segment has several northwest-oriented tributaries. The deep northwest-oriented Panhandle Coulee tributary valleys and the north-northwest oriented Panhandle Coulee headwaters valley were eroded by reversals of flood flow on north-northwest ends of beheaded south-southeast oriented flood flow channels. Note how the south-oriented Cache Creek tributary valleys are linked by through valleys with the north-oriented Jordan Coulee valley and the north-oriented Panhandle Coulee headwaters and tributary valleys. For example in section 35 in the figure east center region a through valley links the south-oriented East Fork Cache Creek headwaters valley with the north-northwest oriented Jordan Coulee headwaters valley. The map contour interval is 20 feet and the through valley floor elevation is between 2660 and 2680 feet. The Papoose Hills to the east rise to elevations greater than 2800 feet. To the west of the through valley there are hills where spot elevations greater than 2780 feet can be found. Through valleys crossing the Panhandle Coulee-Cache Creek drainage divide are much shallower and suggest headward erosion of the east-oriented Jordan Coulee valley (north of figure 6) was caused by south-southeast oriented flood flow moving in an east direction toward what was then probably the newly eroded Rock Creek valley. This east-oriented flood flow eroded the north sloping surface seen in the figure 6 north central and northeast regions and what is now an east-oriented through valley.

Frenchman River-Big Snake Creek drainage divide area

Figure 7: Frenchman River-Big Snake Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 7 illustrates the Frenchman Creek-Big Snake Creek drainage divide area north of the figure 5 map area and including overlap areas with figure 5. Frenchman Reservoir is located near the figure 7 southwest corner and the Frenchman River flows from the figure 7 north edge to Frenchman Reservoir and then to the figure 7 south edge. Rock Creek flows in a south-southwest direction from the figure 7 northeast corner region into the figure 7 southeast quadrant and then turns to flow in south direction to the figure 7 south edge. The unlabeled (in figure 7) south-southeast oriented stream flowing from the figure 7 north center edge, which turns to flow in an east-southeast direction just before joining Rock Creek is Big Snake Creek. West of Big Snake Creek is south-southeast and east oriented Little Snake Creek and west of Little Snake Creek is south-southeast and east oriented Jack Creek. The north-northwest oriented stream joining the east-oriented Jack Creek segment is Jordan Coulee. Panhandle Coulee drains in a north-northwest and southwest direction in the figure 7 southwest quadrant. The north-oriented tributary to east-southeast oriented Big Snake Creek valley segment, and located just west of south-oriented Rock Creek, is Big Coal Bank Coulee. Big Coal Bank Coulee is a classic barbed tributary and like the Jordan Coulee valley the Big Coal Bank Coulee valley was eroded by a reversal of flood flow on the north end of a beheaded south-oriented flood flow channel. Note the shallow west to east oriented through valley extending from the Panhandle Coulee elbow of capture to the east-oriented Jack Creek valley (and then to the south-oriented Rock Creek valley). This through valley was probably eroded headward from the actively eroding south-oriented Rock Creek valley to capture multiple south-southeast oriented flood flow channels and was successful in capturing the flood flow channels on the south-southeast oriented Big Snake Creek, Little Snake Creek, and Jack Creek alignments. At one time the valley probably also received flood flow from channels on the alignment of a south-southeast oriented Panhandle Coulee tributary and also from the south-southeast oriented Frenchman River valley. However, headward erosion of the deep Frenchman River valley and its southwest-oriented Panhandle Coulee tributary valley captured the south-southeast oriented Panhandle Coulee tributary flood flow channel as well as the south-southeast oriented flood flow channels draining to the present day south-southwest oriented Frenchman River valley segment seen in the figure 7 southwest quadrant.

Detailed map of Frenchman River-Big Snake Creek drainage divide area

Fig8FrenchmanBigSnakeCouleeFigure 8: Detailed map of Frenchman River-Big Snake Creek drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 8 provides a detailed topographic map of the Frenchman River-Big Snake River drainage divide area seen in less detail in figure 7 above. The south-oriented Frenchman River valley is located along the figure 7 west edge. Panhandle Coulee drains in a northwest and southwest direction in sections 17 and 18 along the figure 8 south edge (near the southwest corner). Jack Creek flows in a south-southeast direction from the figure 8 north center edge to Nelsons Reservoir and to the figure 8 center and then turns to flow in an east direction. East of Jack Creek Little Snake Creek flows in a south-southeast direction from the north edge to meet east-oriented Jack Creek and then flows in an east direction. Further east near the figure 8 east edge Big Snake Creek flows in a south-southeast direction from the figure 8 north edge to meet east-oriented Little Snake Creek and then flows south a short distance before turning to flow in an east direction to the figure 8 east edge (south half) and to join south-oriented Rock Creek, which is located just east of the figure 8 map area. The figure 8 map contour interval is 20 feet with some dotted contour lines at 10 foot intervals. The drainage divide in the west to east oriented through valley extending across the figure 8 center region is located between the tiny town of Genevieve and the Jack Creek elbow of capture and has an elevation of between 2470 and 2480 feet. Note the floor of this through valley is significantly lower than drainage divides described in figures 4 and 6, both of which are located south of figure 8 and downstream from figure 8 in terms of the Rock Creek and Frenchman River drainage basins. Proceeding north toward the international border elevations in the Frenchman River-Rock Creek drainage divide area rise to more than 3000 feet. As we have already seen elevations of through valleys crossing the drainage divide south of the figure 8 map area are just shy of 2700 feet and some hills on either side of those through valleys rise to nearly 2800 feet. In other words, what may at first appear to be a subtle landscape feature is in fact a 200-300 foot deep (or deeper) west to east oriented through valley linking the south-oriented Frenchman River valley with the south-oriented Rock Creek valley. As already described, prior to headward erosion of the Frenchman River valley headward to the Frenchman Reservoir region, south-southeast oriented flood flow from the upstream Frenchman River valley region flowed in an east direction across the figure 8 map area to what was then the newly eroded south-oriented Rock Creek valley. Headward erosion of the Frenchman River valley (south of the Frenchman Reservoir region captured the upstream Frenchman River drainage basin flood flow.

Frenchman River-Red Mud Coulee drainage divide area

Figure 9: Frenchman River-Red Mud Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 9 illustrates the Frenchman River-Red Mud Coulee drainage divide area just south of the international border. The Frenchman River flows in a south and south-southeast direction from near the figure 9 northwest corner to the figure 9 south edge (west half). The south-southeast oriented Frenchman River  has several south-oriented tributaries in the figure 9 west half and these tributaries from east to west are Red Mud Coulee, Peck Coulee, and Woody Coulee, which is a Peck Coulee tributary. Just east of the figure 9 northwest corner the Frenchman River also has a northwest-oriented tributary, which joins the Frenchman River as a barbed tributary just north of the international border. Note how that unnamed northwest-oriented tributary valley is linked by shallow through valleys with the south-oriented Red Mud Coulee and Peck Coulee valleys. The map contour interval is 20 meters and the through valley leading to the Red Mud Coulee valley has a floor elevation of 880 to 900 meters with elevations rising to more than 920 meters on either side. At least two different shallower through valley link the Peck Coulee valley with the northwest-oriented tributary valley. These shallower through valleys are defined by a single contour line on each side. The valley orientations and the through valleys provide evidence of what were once south-oriented diverging and converging flood flow channels such as are found in anastomosing channel complexes. Headward erosion of the deep Frenchman River valley along what was apparently the most successful of the diverging and converging flood flow channels beheaded and reversed flood flow to the Peck Coulee and Red Mud Coulee flood flow channels so as to erode the northwest-oriented Frenchman River tributary valley and its north-oriented tributary valleys. East of Red Mud Coulee is south-southeast oriented Big Snake Creek (labeled in figure 9 with the word Big) which flows from the figure 9 north center edge to the figure 9 south edge (just east of center) and then to Rock Creek. East of Big Snake Creek is south-southeast oriented Crow Creek, which south of the figure 9 map area joins Rock Creek. East of Crow Creek is south-southeast and south oriented East Fork, which is a Crow Creek tributary. Bluff Creek flows in a south-southeast direction across the figure 9 northeast corner region and is another Rock Creek tributary. Note how just west of the figure 9 center the Red Mud Coulee and Big Snake Creek valleys are linked by a through valley. The through valley suggests the two valleys were initiated as diverging flood flow channels in a south-oriented anastomosing channel complex.

Detailed map of Frenchman River-Red Mud Coulee drainage divide area

Figure 10: Detailed map of Frenchman River-Red Mud Coulee drainage divide area. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

 

Figure 10 provides a detailed topographic map of the Frenchman River-Red Mud Coulee drainage divide area and also of the Frenchman River-Peck Coulee drainage divide area, which were seen in less detail in figure 9 above. The northwest-oriented stream in the figure 10 north center area flows to the Frenchman River (north and west of the figure 10) as a barbed tributary. As seen in figure 10 north-oriented streams in the figure 10 northwest quadrant are tributaries to that northwest-oriented and barbed Frenchman River tributary. Big Snake Creek flows in a south-southeast and south direction near the figure 10 east edge and south and east of figure 10 joins Rock Creek. West of Big Snake Creek is south-oriented Red Mud Coulee, which flows to the figure 10 south edge (east half) and then to the Frenchman River (see figure 9). West of Red Mud Coulee is south-southeast oriented Peck Coulee, which flows to the figure 10 south center edge and then to join the south-southeast oriented Frenchman River, which is west of figure 10. The unlabeled (in figure 10) south-oriented drainage route flowing to the figure 10 south edge west of Peck Coulee is Woody Coulee, which is a Peck Coulee tributary. Note the through valley in the northwest quadrant of section 15 linking the head of the northwest-oriented Frenchman River tributary valley with a south-southeast oriented Red Mud Coulee tributary valley. The map contour interval is 20 feet and the through valley floor elevation is between 2880 and 2900 feet. East of the through valley in the section 10 southeast quadrant a hill rises to more than 3020 feet. Southwest of the through valley in the southeast quadrant of section 16 there is a hill with an elevation of at least 3040 feet. In other words the through valley is more than 120 feet deep and provides evidence of a southeast and south-oriented flood flow channel, which diverged and then converged with a flood flow channel on the present day Frenchman River valley alignment. Near the corner of sections 16, 17, 20, and 21 several closely spaced through valleys link a north-oriented tributary valley draining to the northwest-oriented Frenchman River tributary valley with the south-oriented Peck Coulee valley. The deepest of these through valleys has a floor elevation of between 2960 and 2980 feet. As already noted elevations in the section 16 southeast quadrant rise to more than 3040 feet and west of the through valleys a hill rises to at least 3100 feet. These through valleys provide evidence of another diverging and converging flood flow channel located between what was the Frenchman River valley flood flow channel and the one time southeast and south-oriented Red Mud Coulee flood flow channel. These multiple diverging and converging flood flow channels are characteristic of anastomosing channel complexes and provide evidence that at the time the figure 10 map area was eroded it was being crossed by massive south-southeast oriented floods, first moving to the newly eroded Rock Creek valley and later captured by Frenchman River valley headward erosion.

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.

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