Brahmputra never had competition from Ganges, as simply the width of Brahmputra never is comparable with narrow Ganges (that too after so many mighty river merging into Ganges...n narrower when compared to Brahmputra)!!
The bridge at Brahmputra are outcome after shrinking Brahmputra River flow, making it narrower @ bridge, which often gets criticized, with chances of flood, along with consistent friction arising @ bridge girder, out of compelling water pressure (as wide outflow gets shrinked in narrow flow till bridge, making water pressure increase)!!