First a gelatin could be applied along the sides of the river to provide a buffer to the banks. This would help channel the river and keeping in on course by keeping the water contained. That would be the first phase approach for initial flooding.
Second would be large metal barriers dropped along the banks that are super heated. The flood would be minimized because the water would be converted to steam. Part of the steam could be routed back to continue providing the power to heat the metal.
Third for more extreme flooding an improvement on the sand bagging system would be necessary. Large water permeable casings would quickly be filled with a cement foam that would harden and increase its mass and weight as the water mixed with it. They could be put in place by bulldozers or by workers in exoskeleton suits.
Those are a few ideas.
