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.
-- kevinthenerd, Mar 22 2017

Illustration A https://encrypted-t...XoBNR9UIZuT-wyO1sCA
[not_morrison_rm, Mar 23 2017]

Baked and WKTE. Södertälje, Sweden.

[suggested-for-deletion] redundant, not a new idea.
-- 8th of 7, Mar 22 2017


[8th of 7], my Google is broken. Can you post a link?
-- kevinthenerd, Mar 22 2017


(All of the references I've been able to find so far show the bridge moving.)
-- kevinthenerd, Mar 22 2017


Full marks to [Mr. Thenerd]

(Don't worry about [8th]. He only annotated because he has an umlaut fetish.)
-- MaxwellBuchanan, Mar 22 2017


// show the bridge moving //

That's probably the new "big" bridge at the North end of the channel. Before that, the channel "dived" under the old, fixed bridge. The whole thing was enlarged to let larger ships through.
-- 8th of 7, Mar 22 2017


Umm, if we were talking about bridges, with or without canals, with screw-jacks then that would be handy, seeing as the sea level is rising.
-- not_morrison_rm, Mar 22 2017


//with screw-jacks// and elastic rubber roads.
-- wjt, Mar 23 2017


I was thinking more slidey big bits of steel covered in tarmac.

As the water level rises, they slide out to join the bridge to whatever bit of road is not underwater yet.

See Illustration A, linkey wotsit.
-- not_morrison_rm, Mar 23 2017



random, halfbakery