A Floating bridge is one that crosses a river, estuary, or lake and is supported by pontoons, instead of fixed permanent supports. The first historical records of such bridges date back to the Persians and Greek where the deck was supported on pigskins or boats. These bridges were built for military purposes.
The floating bridge became very popular down through the ages, normally where the erection of fixed foundations was difficult. Besides, the floating bridge technology evolved because of the benefits to military operations. Floating bridges can be assembled on a shoreline and moved over into position with the minimum of labour and machinery in a short period of time.
When the bridge is in position the pontoons are anchored to the river bed to ensure stability. The top of the pontoons may act as the road carriageway or a truss, which is continuous across the pontoons, may also be used.
The main disadvantage of this type of bridge is the high cost of maintenance and its susceptibility to damage from weather events and shipping. In addition the anchoring has to cater for the rise and fall of the water levels