At 5:05PM the pathway along Lady Bird Lake is deluged. Water hit the 15' mark at 12th St just before 5:00PM and would stay above it for 45 minutes.
The USGS data shows that a water level above 15' feet flowed from the 12th St bridge for approximately 45 minutes between 5:00PM-5:45PM.
At approximately 5:20PM Shoal Creek is starting to rage just South of 3rd St.
The West Ave bridge is only 12' high above the pathway and is just 84' long.
Pictured inset: West Ave bridge in Austin, Texas.
At just before 5:30PM on August 22, 2022, when water had just measured at 15.94' at the W 12th St bridge, water flowed under 12' at West Ave.
Local Austin, Texas KXAN weather reporter at the W 4th St bridge at 5:34PM on August 22, 2022.
Worthy of note is that the speed of the water flow up to the West Ave bridge is much slower than past the West Ave bridge, where Shoal Creek makes a sharp turn South at 4th St.
What is interesting about this guardrailing is that it is intact and free of debris and organic matter at the peak time of intense flooding, but was observed to be unmoored the following day on August 23, 2022. SEE BELOW:
Moving North toward 5th St at 5:41PM, it's observed that a very large volume of water neatly and calmly fits under the 5th St bridge.
The W 5th St bridge has 3 tunnels that are 8' high, tucked in a bridge that is 105' long. The images below span left (top) to right (bottom).
At 5:40PM on August 22, 2022, 15.25' of water measured at W 12th St and it headed South to pass under the W 5th St bridge with ease.
South side of the W 5th St bridge at approximately 5:45PM.
North side of W 5th St bridge at approximately 5:50PM on August 22, 2022.
The purpose of posting the USGS data recorded at the W 12th St bridge is to indicate that where I was standing should have ostensibly been submerged in water, but wasn't. 14.85' of water moving South along a progressively narrowing creek to then pass under an 8' bridge can be reasonably considered perplexing to an individual who is clueless to the science of hydrology, or any science, really. It may alos be perplexing to an accredited hydrologist; a goal of this website is to verify as much.
The W 6th St bridge has 3 arched tunnels that are 14' high and a combined 68' wide.
Pictured inset: W 6th St bridge in Austin, Texas.
At 5:58PM on August 22, 2022, when water had just measured at 14.01' at the W 12th St bridge, water cleared through the much smaller W 6th St bridge.
Potentially worthy of note is that the 6th St bridge has at least one (1) storm drain connected to it. Such a drain could add to the volume of water or, perhaps, just add to street-level flooding during intense rain and creek flows.
Just South of 8th St, floodwater had burst out over the creek and into adjacent parking lots. This could reduce the water flow to the W 6th St bridge.
The W 9th St bridge is 10' high above the creek and is 90' long. At approximately 6:10PM, it had a very strong current overwhelming its pathways.
Potential explanation explored.
Does North Lamar Blvd serve to lower water height?
Possibly like the apartment complex near 8th St, perhaps North Lamar Blvd getting flooded in major events prevents overtopping downstream?
If so, why do water heights of 12-13 ft that don't spill out to North Lamar Blvd or the apartment complex come to overtop shorter bridges at narrower passages?
The W 10th St bridge is 14' high at its midpoint above the creek and is 88' long. By 6:18PM it had about 10' of water under it.
Possible answers explored.
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Hazardous events draw attention.
Surprisingly, Shoal Creek is a topic of interest beyond some random guy with a flip phone and an inquisitive personality.
There must be mechanisms at play to account for how dangerous and fast moving water doesn't overtop bridges.
In this summation, the best guesses are provided.