And yet, they are cut down to the same level as the river.
And you would expect otherwise in a old river system canyon?
The rate at which a river cuts into the bedrock is directly related to the water flow rate which is related to the elevation drop of the stream flow.
Lets say for example the main river cuts thru the rock faster due to say a series of large floods in the upper main drainage region. Then the side tributaries would be left behind and an elevation discontinuity where the rivers join (ie waterfall) would occur. This particular region however would wear faster due the elevated flow rates resulting from the greater incline. Over a large period of time the two streams would tend to achieve the same level as they come to equalibrium.
Now what features would be common after a megaflood?
You would expect the presence sheer drop falls. Fine examples exists in the Pacific Northwest at Polouse Falls and Dry Canyon in Washington state. Both created by a megaflood, not the global flood, but the ice age glacial Lake Missoula flood.
Palouse Falls and Lyons Ferry Parkhttp://www.kidscosmos.org/kid-stuff/mars-trip-9.html
The Missoula flood was megaflood that created no meandering caynons.
It appears that all the canyon rim features are common in their appearance and are thus not due to the river since many of them are great distances from the river.
No can follow. What exactly makes you think that the common canyon features exclude the river from forming these features.
I see no evidence here that the river produced all these terrain features.
I see no evidence that the river did not!
Lets just say that if forming a canyon was crime the river here would need a very very good lawyer.
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