Bridge Height Retrofitting

If a municipality builds a drawbridge, then many years later finds that the road and waterway are quite a bit busier than they used to be, one might question the wisdom of saving costs with a short and movable bridge when a tall and stationary bridge might make more sense. However, tearing down an old bridge and rebuilding it is costly and can be politically unpopular.

Herein, I intend to present a way to handle tall maritime traffic under a short bridge. First, the waterway under the bridge is deeply dredged. Then, a rectangular wall is built from the floor of the river to a height well above the highest water level that might ever be expected. The rectangular region is enclosed by two long walls that run parallel to the ship's direction of travel and are placed far enough apart to accommodate the widest ship expected. Perpendicular to the ship's travel are two hydraulic locks, one on each end. First, the tall ship enters the lock. Next, water is pumped out to facilitate clearance. Third, the ship travels through. Fourth, the river is allowed to flood the locks. Finally, the ship continues on its way.