The reasons why a suspension bridge was chosen over other designs were due to two key reasons:
First the Humber River has a shifting bed and is deep enough and wide enough to afford passage to ships, but that is always changing. A suspension bridge with no support piers within the river would not obstruct the estuary.
Secondly, because of the local landscape a construction of a tunnel under the bridge would have been far more costly.
Many different ideas were put forward however over the years, mainly before the knowledge of the Humber had been gained.