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decrease downstream of the basin constriction.
Several meander belts are consistently positioned
to one side of the basin mid-line and suggest
broad tilting in the direction of offset. The
channel constrictions at the basin exits corre-
spond with abrupt transitions from meandering
to straight and typically much narrower river
courses. Several such straight channel reaches
correspond with folds that are visible on the
satellite images and are suggestive of active
uplift. Rivers are diverted toward or around
the end of some of the growing folds, whereas
water gaps have developed across others.
Between growing folds or active thrusts, strike
valleys with little apparent perturbation of
the  river courses are present. The repeated
sequence of braided to meandering to straight
channels suggests that these planform transitions
represent a predictable sequence that can be
used to help recognize localized zones of active
deformation (Attal et al ., 2008).
Third, evidence for contrasting tectonic
regimes can sometimes be inferred through
comparisons of adjacent drainages that display
different channel patterns. A satellite image of
northern Pakistan (Fig. 8.14) shows the Indus
and Kabul Rivers merging and flowing through
a water gap in the Attock Range. At the point of
their merger near where they enter the water
gap, both rivers are responding to the same
local base level. The Indus, now incorporating
the Kabul's discharge, is flowing on or near
bedrock through the Attock Range, which is
experiencing active bedrock uplift (Burbank
and Tahirkheli, 1985). Despite this common
base level, the planform river patterns for each
river upstream from the water gap contrast
strongly with each other: the Indus displays a
strongly braided channel pattern, whereas, at a
comparable distance upstream, the Kabul
shows a nearly straight channel that suggests
active incision of its bed. The braided Indus
may result from aggradation in response to
rock uplift in the Attock Range, but this river
also drains rapidly eroding regions of the
Himalaya, such that its planform pattern may
be attributable to its high sediment load. Why
does this contrast  exist between aggradation
versus incision on adjacent rivers that have a
Impact of Local Rock Uplift
Attock Range
local base
level control
Fig. 8.14 Indus and Kabul Rivers, channel patterns.
Satellite image of the Indus and Kabul Rivers in
northern Pakistan as they join and pass through a water
gap in the Attock Range. Note (i) common base level at
the water gap through the Attock Range, (ii) contrasting
planform river patterns, (iii) zone of inferred
deformation along the Kabul River, and (iv) ponding
(high-sinuosity pattern) upstream of the uplift.
common base level? The likely cause can also
be inferred from the  satellite image, which
suggests that both upstream and downstream
controls are important. Linear trends both east
and west of the Kabul River delineate active
transpressional faults (Fig. 8.14). The zone of
uplift, delineated by lighter colored, less vege-
tated areas, extends across the Kabul River
toward the east-northeast and lies north of the
Indus River. Throughout this uplifting reach, the
Kabul River is incising. Just upstream of this
zone, however, the river displays meanders, cut-
offs, and swampy regions indicative of low
gradients. These features suggest that the Kabul
system is ponded upstream of the uplift, whereas,
when crossing the zone of active rock uplift,
the  channel narrows and straightens, thereby
increasing its gradient and specific stream power.
It is remarkable how much tectonic informa-
tion can be inferred from planform river patterns
such as these! Such interpretations can be
reinforced when analysis of planform patterns
is combined with structural interpretations of
stratal geometries or with local drainage patterns
that are indicative of growing folds and faults.
The widespread availability and ever-increasing
quality of remotely sensed imagery allows for
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