Page 186 - Fundamentals of Geomorphology

HILLSLOPES 169

Wood
(1942)
Ruhe
(1960)
Waxing slope
Savigear Summit W axing slope
Summit
Dalrymple et al . (1965) F Free face
face
ree
Shoulder
(1968) Upland flats Shoulder
Upland flats
Constant slope
Constant slope
Interfluve Crest slope
nterfluve
I
Crest slope
Backslope
Seepage slope
Seepage slope Backslope
slope
aning
Waning slope
W
creep
slope
Convex creep slope
Convex
Midslope
Midslope
all
face
F Fall face
Footslope
ootslope
F
T Transportational slope
ransportational
slope
oeslope
Toeslope
T
ootslope
F Footslope
Lowland
flats
footslope
Colluvial footslope Lowland flats
Colluvial
Alluvial toeslope
Alluvial
toeslope
Figure 7.3 Systems for naming hillslope elements.
and lower wash slope (Wood 1942). A widely used sys-
tem has five slope units – summit, shoulder, backslope, Free
face
footslope, and toeslope (Figure 7.4) (Ruhe 1960). A sim-
Summit
ilar system uses different names – upland flats (gradient Summit
Shoulder
less than 2 ), crest slope, midslope, footslope, and low- Shoulder
◦
Backslope
land flats (gradient less than 2 ) (Savigear 1965). The Backslope
◦
Footslope
Toeslope
nine-unit land-surface model embraces and embellishes Footslope
all these schemes and distinguishes the following units – Toeslope
interfluve, seepage slope, convex creep slope, fall face,
transportational slope, colluvial footslope, and alluvial
toeslope (Dalrymple et al. 1968).
Different slope processes tend to dominate the var-
ious slope elements along a catena. On convex slope
segments, commonly found on the upper parts of hill- Figure 7.4 Ruhe’s (1960) slope units.
slope profiles, soil creep and rainsplash erosion dominate,
at least when slopes are below the threshold for rapid mass
wasting; subsurface movement of soil water is also impor-
tant. Where convex segments are steeper than about 45 , elements are commonly sites of transport and deposition.
◦
fall, slide, and physical weathering are the chief pro- They usually develop near the base of hillslope profiles in
cesses. Straight (mid-slope) elements usually receive a situations where waste material moving down the hillside
large amount of material from upslope by mass wast- through mass wasting and surface and subsurface water
ing processes (including flow, slump, and slide), surface action comes to rest and rivers at the hillslope base do
wash, and subsurface water movement. Concave slope not remove it.