Weighted flow accumulation: using deforestation as weight?

Right off the bat: if a small river has 10% of its upstream catchment deforested, and a big river has 5%, I want that small river to have higher output values. But now it won’t because of how much more flow accumulation the big river has.

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I need to figure out which rivers in a certain area have the most potential influence from upstream deforestation.

So, I used ArcGIS Pro to calculate flow accumulation with my deforestation raster with pixel values ranging from 0 – 1.

The result, of course, still is biased towards bigger rivers with more flow accumulation.

Any idea on how I can separate flow accumulation from deforestation values?