Savanna/Sebulba Bridge (IA)

[SSOWorld]

http://www.news.iowadot.gov/newsandinfo/2018/02/mississippi-river-overflow-bridge-on-us-52-north-of-sabula-closed-iatraffic.html

An overflow bridge got the road closed.  Probably didn't intend for a closure but it happened.

[pianocello]

Um... Sabula?

Kind of a shame, the main bridge just got replaced this past year. I went to check it out over Thanksgiving, and there was still work that needed to be done on the approaches. Hopefully crews can use this opportunity to speed up that process, if it hasn't been completed since then.

[Scott5114]

Pretty sure Sebulba is a Pokemon that can only be caught in Iowa

[Rothman]

Sebulba = Evil pod racer in Episode I.

[iowahighways]

They were supposed to replace the overflow bridge this year anyway, but it wasn't supposed to close until April. (article).

And it looks like a local resident is boating residents across the river until the bridge reopens. (article)

[CtrlAltDel]

What is an overflow bridge?

[Mapmikey]

What is an overflow bridge?

Many rivers when they get high end up having flow run into other channels that would require a separate bridge for highways to cross.  When it is not flooding, sometimes these overflow channels have little or no water in them.  The overflow channels can be natural or man-made and are especially prevalent in swamps...

[MNHighwayMan]

That whole US-52 causeway/bridge, and even the town of Sabula itself, doesn't even look like it should exist. How do they not get regularly overrun with flood water?

[paulthemapguy]

I was really frustrated that I didn't find out about the Friday, March 9th implosion until it was too late.  I was already on a trip to Traverse City Monday through Thursday, and knew I couldn't justify taking off the following Friday to see the bridge be detonated (if that's the right word).

[DeaconG]

That whole US-52 causeway/bridge, and even the town of Sabula itself, doesn't even look like it should exist. How do they not get regularly overrun with flood water?

Levees?

[sparker]

What is an overflow bridge?

Many rivers when they get high end up having flow run into other channels that would require a separate bridge for highways to cross.  When it is not flooding, sometimes these overflow channels have little or no water in them.  The overflow channels can be natural or man-made and are especially prevalent in swamps...

One of the most prominent examples of this is the Yolo Bypass, bridged by the Yolo Causeway on I-80 west of Sacramento.  During flood conditions weirs are opened in the Sacramento River levee just downstream from the Feather River confluence (the latter drains much of the east Sacramento Valley) and overflow water enters the bypass, itself defined by levees on either side of the 2-mile-wide channel (used for rice farming in the interim); the outflow drains into the deep Sacramento Ship Channel.  But in most years the Bypass remains dry.

It's likely that several such channels -- probably some of them naturally formed -- are part of the Mississippi River floodplain in that area, receiving river water in particularly wet conditions.  Both CP (west side) and BNSF (east side) have major rail corridors on the river banks, located on berms that are high enough to keep most water (except in extreme conditions) from flowing to the side, forcing it into channels within the major floodplain.  But during exceptionally rainy seasons (such as back in 1993), the tracks -- and indeed the whole low-lying valley -- can be completely inundated. 

[Highway63]

Sebulba = Evil pod racer in Episode I.

Pod racing over the old bridge would have been a really, really bad idea.

[iowahighways]

Thread bump: the overflow bridge opened on August 31. Quad-City Times story