Fluvial Processes Erosion headward dissection vertical incision
lateral migration Transport bed load suspended load dissolved load
Deposition deltas natural levee backswamp alluvial fan
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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
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Braided Stream Platte River near Louisville, NE
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Landscape: flood plain, river valley; Landforms: meanders,
oxbow lake, scroll bar ; Laramie R., WY Wysocki
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Ritter et al., 1995
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( Ritter, et al., 1995 )
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Benoit MS, AR USGS 7.5 quad
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MS River Oxbow Deer Creek Source
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Wysocki Holocene clay capped stream terrace (Sharkey soil);
Washington Co., MS
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Wysocki Sharkey soil profile ; Washington Co., MS Sharkey
Series very fine, Chromic Epiaquert
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Wysocki Natural levee to backswamp transition. Dundee Series
Fine Silty Typic Endoaqualf Sunflower Co. MS
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Landscape: river valley; Landforms: scroll bars, oxbows,
channelized river ; Miss. R., AR / MS Wysocki
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Landscape: loess-covered till plain; Landform: entrenched
stream, meanders; Lincoln, NE Wysocki
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( NASA id 16633 ) Landscapes : river valley, gulf (water)
Landforms : delta (birds foot) channel, natural levee Mississippi
R., LA (1999; natural color)
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Landform: stream terraces ; Snake R., near Jackson Hole, WY
Wysocki
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Landforms: canyon, strath terrace; Black Canyon (Gunnison R.),
CO Schoeneberger
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Fill Terrace
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Erosional terrace
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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
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Landforms : low mountains, interfluves, alluvial fan, braided
river ; Brodeur Peninsula, Baffin Is, Nunavut, CAN ( GSC#2002-205
)
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Insert graphic from Lambert, 1996 ( NM, 2002 ) Landform:
alluvial fan; Parent Material: fan alluvium; Organ Mountains, Las
Cruces, NM Schoeneberger
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Landform: alluvial fan ; Death Valley, CA. What is the grayer
deposit to left?
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Landform: alluvial fan; Cedar Creek Fan MT Ennis, MT USGS 7.5
Quad
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Ritter, et al, 1995
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How do you distinguish a low gradient alluvial fan from a
stream terrace?
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One Mile Alluvial Fans Stream Terrace
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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
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( 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 :
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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
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Landscape: bajada in a semi-bolson ; Landforms: ballena, eroded
fan remnants, eroded fan-remnant sideslopes, inset fan, terraces ;
Organ Mountains., Las Cruces, NM Schoeneberger
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Hillslope Evolution : back wearing side slopes and
pedimentation S = ?? a = ?? P = ?? c = ?? ps = ?? ( Peterson, 1981;
fig. 16 )
( Peterson, 1981; fig. 9 ) p - ( partial ballenas ) s - (
relict summit area )
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Landscape: bajada in a semi-bolson ; Landforms: eroded fan
remnants, eroded fan- remnant sideslopes ; Organ Mountains., Las
Cruces, NM Schoeneberger
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( 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
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Landscape: bajada ; Landform: eroded fan remnants, inset
terraces ; Tortugas Mtn. view (Organ Mountains., Las Cruces, NM )
Schoeneberger
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( 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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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
