Why rivers are oblique to mountains?

Why rivers are oblique to mountains?

Rivers are the by-product of tectonic and climate. So, when rivers are not where we expect they should be, we can invoke either tectonics or climate…

For instance if rivers are oblique to the main geological features (plateau limit or faults), we may think about blaming tectonics for this geometric anomaly.
Why?
Because strike-slip tectonics shear landscape,
and because river beds belong to landscape.
This was suggested by Seb Castelltort and his colleagues for New-Zeland from data supported by numerical simulations (with DAC, a landscape evolution program written by Jean Braun from Rennes Grenoble), [Castelltort et al. (2012), River drainage patterns in the New Zealand Alps primarily controlled by plate tectonic strain, Nature Geosci, 5(10), 744-748]

That’s sit? May be not…
Rain is partly controlled by wind.
Wind is controlled by the large-scale atmospheric circulation.
Wind is not controled by tectonics.
Rain is partly controlled by topography: the windward sides of mountains are wetter than the leeward
Besides, orography is remarkable in New-Zealand.
Rain controls erosion.
Erosion controls topography…

So what… Let imagine what could happen to rivers if the wind is oblique to the main mountain boundary. The simulations are due to EROS.

Conclusion: Still a headache for geomorphologists…