Does anyone know of any bridges that sit low over water?
The Conowingo Dam over the Susquehanna River along U.S. Route 1 between Darlington and Conowingo, Maryland, although I'm not sure if that's a bridge by the strictest definition.
The bridge portions of the Chesapeake Bay Bridge-Tunnel are pretty low. So are segments of the Nice Bridge carrying U.S. Route 301 over the Potomac River between Virginia and Maryland.
OP is probably thinking more along the lines of this bridge connecting two Virginia prisons across the James River a little west of Richmond:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fwww.vahighways.com%2Fbridges%2Fyoulle2.jpg&hash=abbb1fd162918ec9bb90ced1ad6852456f5bdd0e)
Another example over the Shenandoah River (being replaced). This 1925 structure was part of VA 12 for a few years up to 1942:
https://goo.gl/maps/zf2UdcKZ6ZD2
Quote from: ColossalBlocks on January 15, 2017, 06:18:49 PM
Does anyone know of any bridges that sit low over water?
How low do you want to go? In California, we have tidal-level ferries on State Highways (CASR-222?) that take cars less than a meter above the water level.
I am unaware that the California State Highway system has any floating bridges, but the southern bridges across the San Francisco bay (CASR-84 and -92) have causeway sections that are just high enough to keep safely above high tide and a decent swell. A high gusty windy storm (uncommon because it would have to do some things that wind storms don't often do) will cause splash up and close some of the lanes. The same happens on the Yolo Causeway on I-80.
Build up high (so that ocean-going vessels can get underneath) and deal with high wind warnings. Build down low and deal with splash up.
In my experience, the bridges across major rivers that don't have ocean-going vessels are built high enough so as to get just above the levees.
If a river is navigable in any significant way the Coast Guard has a say in bridge height
LGMS428
Quote from: jwolfer on January 17, 2017, 12:44:52 AM
If a river is navigable in any significant way the Coast Guard has a say in bridge height
As does the Army Corps of Engineers (maybe even more so than the Coast Guard).