Update 2022-02-09: US 41 Little Alapaha River Bridge.
Here is a bit more about the Little Alapaha River: map, Source, Bridges (one wooden), Confluence, where two days ago we found the Alapaha River running into the Little Alapaha River as a distributary.
First, a map.
According to the USGS trace and googlemaps, the source of the Little Alapaha River is just north of the GA-FL line, on private land in Echols County, Georgia. It might be a spring, but more likely it’s just overflow from various bays and swamps north of it. That turns out to be 10.9 river miles upstream from the Little Alapaha River Confluence with the Alapaha River, according to WWALS river mile software.
For bridges, I turned to BridgeReports.com, National Bridge Inventory Data:
BridgeReports.com is a searchable version of the National Bridge Inventory (2019 edition), a database of 628,207 bridges on public highways in the United States.
There we find
four five bridges over the Little Alapaha River.
Click on the header for each for more detail.
For pictures we resorted to Google Streetview.
“67.3-foot 5-span wood stringer bridge built in 1989.” Yes, really, a wood bridge built in 1989.
At Little Alapaha River mile 0.57, a series of swallets usually swallows the entire river. That’s on private property, about 1.2 miles east of the US 41 Alapaha River Bridge (1.38 miles via US 41) and 0.28 miles north of US 41.
For those not familiar with the term, a swallet is an opening to an underground stream. So a swallet can act as a spring or a sinkhole depending on weather conditions and water levels. A swallet is also known as a karst window, as in karst, the porous limestone that underlies the whole region, and contains our underground water, including the Floridan Aquifer.
We know this location because of Southeastern Geological Society (SEGS), Guidebook No. 63, November 7-8, 2014, KARST HYDROGEOLOGY OF THE UPPER SUWANNEE RIVER BASIN, ALAPAHA RIVER AREA, HAMILTON COUNTY, FLORIDA, which says:
The Little Alapaha River, for example, enters the Floridan aquifer approximately 1.2 mi. east of the Alapaha through a large, complex swallet….
That’s the Floridan Aquifer, which along with other underground water is the source of almost all water for drinking, agriculture, and industry in south Georgia, most of Florida, and parts of South Carolina and Alabama.
Most of the rivers that cross the Cody Escarpment (Cody Scarp), an ancient coastline, go underground (except the Withlacoochee and Suwannee). Many people think of the Cody Scarp as a simple east-west more or less straight line. It’s much more complicated than that, as witness the complex Little Alapaha River swallet. Plus see below about probably are more sinkholes farther south.
Update 2022-02-09: Actually, there is a US 41 Little Alapaha River bridge, and it may even be historic.
It’s the first bridge in bridgereports.com for Hamilton County, mislabled as “US-41 (SR-6 & 25) over ALAPAHA RIVER OVERFLOW”. But at 30.52389, -83.01550 At more than a mile east of the Alapaha River, that’s a bit far to be overflow.
It’s also about a thousand feet east of where the USGS track for the Little Alapaha River crosses US 41. Apparently USGS was making a schematic trace of approximately where they think the river travels underground.
You can sort of make out an empty river valley north of the bridge, coming down from the swallet, where most of the water most of the year goes into the Floridan Aquifer. And in google streetview you can see that valley.
South of the bridge, the aerial view shows the river turning sharply to the east before heading south. And that’s what we see in google streetview looking southeast.
The bridge itself turns out to be possibly historic, presumably because of how old it is:
Purpose: Carries highway over relief for waterway
Route classification: Minor Arterial (Rural) 
Length of largest span: 22.0 ft. [6.7 m]
Total length: 86.9 ft. [26.5 m]
Roadway width between curbs: 27.6 ft. [8.4 m]
Deck width edge-to-edge: 31.2 ft. [9.5 m]
Owner: State Highway Agency 
Year built: 1922
Year reconstructed: 1947
Historic significance: Bridge is possibly eligible for the National Register of Historic Places 
Design load: M 13.5 / H 15 
Number of main spans: 4
Main spans material: Concrete 
Main spans design: Slab 
Deck type: Concrete Cast-in-Place 
Wearing surface: Bituminous 
It’s not in very good shape, though.
Latest Available Inspection: November 2018
Good/Fair/Poor Condition: Fair
Status: Open, no restriction [A]
Average daily traffic: 3,800 [as of 2017]
Truck traffic: 12% of total traffic
Deck condition: Good [7 out of 9]
Superstructure condition: Good [7 out of 9]
Substructure condition: Satisfactory [6 out of 9]
Structural appraisal: Equal to present minimum criteria 
Deck geometry appraisal: Basically intolerable requiring high priority of corrrective action 
Water adequacy appraisal: Equal to present desirable criteria 
Roadway alignment appraisal: Equal to present desirable criteria 
Channel protection: Bank protection is in need of minor repairs. River control devices and embankment protection have a little minor damage. Banks and/or channel have minor amounts of drift. 
Scour condition: Bridge is scour critical; bridge foundations determined to be unstable. 
Sufficiency rating: 77.5
Nonetheless, there is a US 41 Little Alapaha River Bridge.
Here’s what we saw two days ago at the Little Alapaha River Confluence.
The Jennings Gauge read 67.8′ NAVD88.
Nobody wanted to go very far in there, because the current was rushing in strongly, making the Little Alapaha River a distributary.
So Helen also came back out.
But of course I had to go in, with the WWALS GOPRO 360 camera.
It’s a little hard to believe that Alapaha River water goes up the Little Alapaha River the whole 0.57 miles to the Swallet,
considering there is no US 41 Little Alapaha River bridge.
Maybe there are more sinkholes or swallets closer.
The Confluence is on land owned by the Suwannee River Water Management District (SRWMD),
so maybe they know something.
-jsq, John S. Quarterman, Suwannee RIVERKEEPER®
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