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Fluvial Processes and Geomorphic Environments. Fluvial Processes Erosion headward dissection vertical incision lateral migration Transport bed load suspended.

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Presentation on theme: "Fluvial Processes and Geomorphic Environments. Fluvial Processes Erosion headward dissection vertical incision lateral migration Transport bed load suspended."— Presentation transcript:

1 Fluvial Processes and Geomorphic Environments

2 Fluvial Processes Erosion headward dissection vertical incision lateral migration Transport bed load suspended load dissolved load Deposition deltas natural levee backswamp alluvial fan

3 Fluvial erosion, transport, and deposition by flowing water. des excludes glaciofluvial systems Sediments: coarse to fine grained, commonly stratified; texture and morphology depends upon deposition environment Landscapes: alluvial plain, canyonlands, river valley Landforms: arroyo, flood-plain step, meander, stream terrace Microfeatures: bar, groove, gully

4 Braided Stream Platte River near Louisville, NE

5 Landscape: flood plain, river valley; Landforms: meanders, oxbow lake, scroll bar ; Laramie R., WY Wysocki

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11 Ritter et al., 1995

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13 ( Ritter, et al., 1995 )

14 Benoit MS, AR USGS 7.5’ quad

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19 MS River Oxbow Deer Creek Source

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21 Wysocki Holocene clay capped stream terrace (Sharkey soil); Washington Co., MS

22 Wysocki Sharkey soil profile ; Washington Co., MS Sharkey Series very fine, Chromic Epiaquert

23 Wysocki Natural levee to backswamp transition. Dundee Series Fine Silty Typic Endoaqualf Sunflower Co. MS

24 Landscape: river valley; Landforms: scroll bars, oxbows, channelized river ; Miss. R., AR / MS Wysocki

25 Landscape: loess-covered till plain; Landform: entrenched stream, meanders; Lincoln, NE Wysocki

26 ( NASA id ) Landscapes : river valley, gulf (water) Landforms : delta (birds foot) channel, natural levee Mississippi R., LA (1999; natural color)

27 Landform: stream terraces ; Snake R., near Jackson Hole, WY Wysocki

28 Landforms: canyon, strath terrace; Black Canyon (Gunnison R.), CO Schoeneberger

29 Fill Terrace

30 Erosional terrace

31 Alluvial Fans Alluvial fans compared to perennial streams – cross-sectional profile - longitudinally convex –flashy flow system – sediment composition: Degree of Sorting - < stream alluvium Degree of Rounding - < stream alluvium Clast supported - > stream alluvium –debris / mudflow - common in proximal areas

32 Landforms : low mountains, interfluves, alluvial fan, braided river ; Brodeur Peninsula, Baffin Is, Nunavut, CAN ( GSC# )

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36 Insert graphic from Lambert, 1996 ( NM, 2002 ) Landform: alluvial fan; Parent Material: fan alluvium; Organ Mountains, Las Cruces, NM Schoeneberger

37 Landform: alluvial fan ; Death Valley, CA. What is the grayer deposit to left?

38 Landform: alluvial fan; Cedar Creek Fan MT Ennis, MT USGS 7.5’ Quad

39 Ritter, et al, 1995

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41 How do you distinguish a low gradient alluvial fan from a stream terrace?

42 One Mile Alluvial Fans Stream Terrace

43 active alluvial fan fan remnant ( fan surface abandoned but substantially intact; inset fan-head trenches, terraces) eroded fan remnant ( little fan surface remains; e.g. < 50 % of original fan surface ) eroded fan remnant sideslopes ( no fan surface remains; hillslope elements dominate ) original fan surface Evolutionary stages of alluvial fan landforms ( cross-sectional profiles ) PJS, 2004 Inset fan

44 ( Peterson, 1981; fig. 3 ) Basic Landform elements of Basin & Range terrain – southwestern US A - alluvial fan B - ballenas F - alluvial flat M - mountains (LS) P - fan piedmont (LS) S - fan skirt Y - playa bolson, semi-bolson Landscape :

45 A - alluvial fan V - interfan valley P - fan piedmont ( Peterson, 1981; fig. 7 ) Drainageway Types (FFP). 1 - interfan - valley drainageway 2 - fanhead trench 3 - onfan drainageway 4 - interfan-valley drainageway Inset fan fan remnant

46 Landscape: bajada in a semi-bolson ; Landforms: ballena, eroded fan remnants, eroded fan-remnant sideslopes, inset fan, terraces ; Organ Mountains., Las Cruces, NM Schoeneberger

47 Hillslope Evolution : back wearing side slopes and pedimentation S = ?? a = ?? P = ?? c = ?? ps = ?? ( Peterson, 1981; fig. 16 )

48 ( Peterson, 1981; fig. 15 ) Hillslope Evolution & Hillslope - Profile Positions: - 2 dimensional - backwearing slope convergence - divide lowering

49 ( Peterson, 1981; fig. 9 ) p - ( partial ballenas ) s - ( relict summit area )

50 Landscape: bajada in a semi-bolson ; Landforms: eroded fan remnants, eroded fan- remnant sideslopes ; Organ Mountains., Las Cruces, NM Schoeneberger

51 ( adapted from Peterson, 1981; fig. 17 ) c = crest m = summit s = shoulder b = backslope f = footslope t = toeslope x = drainageway Variations of hillslope-profile positions in southwestern US Landscapes

52 Landscape: bajada ; Landform: eroded fan remnants, inset terraces ; Tortugas Mtn. view (Organ Mountains., Las Cruces, NM ) Schoeneberger

53 ( Peterson, 1981; fig 11 ) 1 - original fan surface 2 - first gullying sequence ( or its remnants of pediments, footslopes ) 3 - second gullying sequence ( or its remnants of pediments, footslopes ) 4 - third gullying sequence ( or its remnants of pediments, footslopes ) Landscape Evolution : Typical Erosion Sequences of Fan Piedmonts Generalized (Erosional) Evolution of Divides a – relict fan-piedmont surface (1) b - asymmetric, relict fan piedmont surface and new, encroaching pediments c - ridgeline remnants of pediments 2 & 3 d - late stage erosion of “c”

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55 Landform : slot canyon Escalante Natl. Mon., UT Schoeneberger slot canyon – A long, narrow, deep and tortuous channel or drainageway with sheer rock walls eroded into sandstone or other sedimentary rocks, especially in the semi-arid western USA (e.g. Colorado Plateau); subject to flash flood events; depth to width ratios exceed 10:1 over most of its length and can approach 100:1; commonly containing unique ecological communities distinct from the adjacent, drier uplands. NSSH


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