If you think about this for a minute, you'll realize that what you're asking for is pretty much impossible.

What would these artificial islands be made of? Sand, gravel, concrete rubble? This is a river, the constant current of the water erodes anything that resists it by staying in place. Piling up enough material to resist erosion and create a meaningful obstacle to 70000 tonnes in motion, that would significantly narrow and make shallow the navigable waterway. The only way to do this is to build giant underwater concrete towers -- basically the structures pylons typically rest on, the piers. Look up the process required to build these, it's quite an undertaking. They are engineered to withstand the pressure of ice floes every spring, they're not flimsy by any measure.