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River Capture (stream piracy) - Coggle Diagram
River Capture (stream piracy)
Abstraction
the lowering and shifting of a watershed
can happen wherever a river flowing down one side of a watershed is more energetic than the river flowing down the other side.
the overgraded river erodes and deepens the valley at the source more efficiently
there is no longer any support at source, the ground collapses and the river now starts flowing from a higher point
the river lengthens by
headward erosion
, gradually cutting back the watershed
the watershed will be lowered and it will be pushed back from the overgraded river
the
headwaters
of the river flowing on the left, now drain into the river on the right.
Volume: if there is higher rainfall on one side of the watershed, the river with have greater volume and so erode more efficiently
Rock Resistance: softer rock on one side of the watershed will allow rivers to erode deeper and more quickly than more resistant rock on the other side of the watershed
River Capture
Before capture:
as River A is flowing down a steeper slope and to a lower level than River B, the part of River B that is upstream will now flow down into River A
the point where River A meets River B:
elbow of capture
eventually River A reaches River B because the watershed has been lowered and shifted away from River A by abstraction
Therefore River A is more energetic than River B and lengthens itself by headward erosion, causing abstraction
River A is flowing down to a lower point that River B
River A is flowing down a steeper gradient than River B
River B is on one side of the watershed and River A is on the other side
the section of River B above the elbow of capture that now flows into River A:
captured stream
River A is
captor stream
River B's volume of water downstream is now drastically reduced.
a
wind gap
develops in the valley above the misfit stream where River B used to flow but has now dried up because its headwaters have bee diverted to River A