If I read the information correctly, the flood zone is 'X Shaded" and is defined as:

Between the limits of the100-year and 500-yearFlood plain, area with a 0.2% (or 1i n 500 chance) annual chance of flooding. Source FEMA Fllood Zone Designation.

The 2024 Kerr County Hazard Mitigation Plan has this to say:

In the case of the FEMA 100-year floodplain there is a 1% annual chance, while in the 500-year floodplain there is a 0.02% annual chance. Thus, the likelihood of a 100-year flood event is occasional and the likelihood of a 500-year flood event is unlikely. However, based on the frequency of previous flood events, every jurisdiction can expect to experience some type of flooding that may or may not meet the definition of a 100-year or 500-year event on a more regular basis. The local planning team determined it is likely that Kerr County and the participating jurisdictions will experience a flood event in the next year, meaning an event is probable in the next three years. 3) Extent Flood magnitude is generally measured by depth of flood waters in feet or inches. Throughout Kerr County and the participating jurisdictions, recent flood events have resulted in up to 10" of flood water. Future worst-case flood events in Kerr County and the participating jurisdictions may meet or exceed previous worst-case 10" flood depths.

So, can someone tell me if the data from the 1987 flood would have been used to benchmark their determinations?

As to plans- in this case Mother Nature had a big VOTE.

For your area at 281 and the Guadalupe, the Q25 event would have 8.97 inches of rain in a 24 hour period. For Q50 10.8 and for Q100 13.1. In a one hour duration you're looking at 3.48, 3.96, and 4.48 respectively.

Point is, you're going to see a lot of intense flooding in that area with not a lot of difference between the Q25 and Q100 events.

I think to put it in a localized perspective, what storm event was 12-inches in a 3-hour storm?

I assume larger than 500-year, but do not have the chart in front of me

12 inches in a 3 hour duration would be off the chart. But I've not seen that amount reported anywhere.

I've send reports of 10" about a mile away from Mystic and north of 12" a bit farther away "during the flash flood period". I cannot figure out what time period that covers though.

Alta said:

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I've send reports of 10" about a mile away from Mystic and north of 12" a bit farther away "during the flash flood period". I cannot figure out what time period that covers though.

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That is my general understanding and I have not seen data to support a 3-year duration, but know it was not over a 24-hour period.

I also read that the rainfall intensity was varying widely in the storm depending on where you were. The Guadalupe has a pretty large catchment area as well, so determining the contributing amounts for Mystic would occur further upstream.

Teslag said:

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12 inches in a 3 hour duration would be off the chart. But I've not seen that amount reported anywhere.

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I cant even imagine that. Imelda in Houston was that type of rain...even with no hills the flooding was somewhat dangerous. In the hill country that amount would nearly move mountains. terrible!


I am a river / lake dweller and have been my entire life. No reason to try and make sense of flood plains. I am sure many will try via court, but it will fail. I cannot imagine the camp or any RV park had a disclaimer on the contract saying "we are not in a flood plain and our camp is not prone to flash flooding."


The water is fun to live and camp beside. Make no mistake, it is only fun 99.99% of the time. Very few have the misfortune of seeing the .01%

Rainfall/flow in a localized upper reach is fairly easy to determine before it disperses into the larger watershed.

The intent is this was not a 100-year or 500-year event due to the short duration of the storm.

Take this link for what it is worth:

https://www.mlive.com/weather/2025/07/rain-data-shows-why-texas-camp-mystic-area-was-ground-zero-for-deadly-wall-of-water.html

Ingram, Texas had 12.71 during the flash flooding period.


It wasn't just a localized area of heavy rain. Other rain gauges reported over a foot of rain and the larger area had over 5 inches of rain.

I'm 15 miles from 281 and the Guad. We got almost 5 inches in a single hour before it let up on Saturday at my house.

That system was absolutely capable of 12 inches in 3 hours if it sat and didn't stop.

I am going to get my self study CEU today.

Rainfall chart for the area and my thoughts on where the rainfall event was (i still have not seen actual rainfall broken down by the hours):

Ya, "flash flooding period" is awfully loose.

I looked at it closer and it appears their "flash flooding period" is total rainfall from July 3rd to July 7th. So the 12.7 inches of rain at Ingram would be over a 4 day period. That would put it around a 50 year storm event.

Teslag said:

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For your area at 281 and the Guadalupe, the Q25 event would have 8.97 inches of rain in a 24 hour period. For Q50 10.8 and for Q100 13.1. In a one hour duration you're looking at 3.48, 3.96, and 4.48 respectively.

Point is, you're going to see a lot of intense flooding in that area with not a lot of difference between the Q25 and Q100 events.

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I don't remember the timeline cause I'm old now but in 02, in either a 4 or 5 day period the first week of July, we had 36 inches of rain at our place ........I don't know how much fell overnight in one event but I had put out a turkey frying pot one evening and the next morning it was overflowing and it's 17 inches deep. Down on the river itself I helped a neighbor move some stuff and his house was built with a second story living area and the first story was garage and laundry/ storage area with double garage doors on both the upstream and downstream side and water was flowing through We had been imbibing on some adult beverages and the owners wife was pretty snockered. We sat out on the street and watch as things floated out of the garage.......she said "there foes our Fing washer, then there goes our fing dryer, there goes our fing freezer. Their propane tank was bobbing in the water like a cork.

This recent event resulted in a 29 foot rise.....the 02 event was 44 ft

I don't think that is accurate though. There are maps out there where you can narrow the window down I just can't get it down to only a 3 hour period. There are rain gauges that show 10" of rain on just the 4th. Reasonable to think most of that fell in the early morning hours of the 4th and these rain gauges are different then the ones showing the most rain.

Alta said:

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I don't think that is accurate though. There are maps out there where you can narrow the window down I just can't get it down to only a 3 hour period. There are rain gauges that show 10" of rain on just the 4th. Reasonable to think most of that fell in the early morning hours of the 4th and these rain gauges are different then the ones showing the most rain.

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I can't confirm the validity of any of it, just that his data source was using a 4 day range for their flooding period totals.

Agree...the definition is loose and I/we know it rained like hell that night.

I just have not had time to look for the data to support my thoughts.

And I think it will be some time before we have some really good data on this event/storm. Still way early.

The data is there, I just have to figure out how to get the historical data:


https://www.gbra.org/conditions/






Kerr County is further down.

Yes, based on the data that I can see certainly a 500 year rain event and probably 1000 year in certain spots very close and upstream of Mystic. About as extreme of a weather event as we can get, especially in this region.

Alta said:

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Yes, based on the data that I can see certainly a 500 year rain event and probably 1000 year in certain spots very close and upstream of Mystic. About as extreme of a weather event as we can get, especially in this region.

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I think that's a big assumption at this point until we get something verifiable.

tamc93 said:

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The data is there, I just have to figure out how to get the historical data:


https://www.gbra.org/conditions/






Kerr County is further down.

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FOIA?

https://www.wunderground.com/dashboard/pws/KTXHUNT85/table/2025-07-4/2025-07-4/daily

Roughly 9.7 inches in 4 hours (guage must have stopped working later on):

Teslag said:

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Alta said:

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Yes, based on the data that I can see certainly a 500 year rain event and probably 1000 year in certain spots very close and upstream of Mystic. About as extreme of a weather event as we can get, especially in this region.

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I think that's a big assumption at this point until we get something verifiable.

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Of course it is - what actually is a 500 year and 1000 year rain event is based off of very large assumptions. But you can pull data and see and plug into that chart that was posted on here. No idea if the rain gauges/doppler are accurate, etc. I can't figure out how to post things into this thread when you have to use maps/filters to capture the data.

Looks like from swc93's other data it's around 200 year thereabouts

tamc93 said:

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https://www.wunderground.com/dashboard/pws/KTXHUNT85/table/2025-07-4/2025-07-4/daily

Roughly 9.7 inches in 4 hours (guage must have stopped working later on):

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that's what i was looking for a weather system like that or someone's personal ambient or davis station that had the data.

Teslag said:

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FOIA?

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I get paid to do those .

tamc93 said:

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Teslag said:

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FOIA?

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I get paid to do those .

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Too bad I no longer work for the Corps. We got paid to waste time and do nothing.

Teslag said:

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tamc93 said:

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Teslag said:

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FOIA?

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I get paid to do those .

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Too bad I no longer work for the Corps. We got paid to waste time and do nothing.

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this explains so much.

Don't worry, only spent 4 years there. Back in private side now and for most of my 20+ years.

Will do. It was clarified later that the victim cabins were still in it however

Teslag said:

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Possibly, hard to say without the supporting exhibits which cabins were included in the LOMR determination. One thing to point out is that I think I saw that those in Bubble Inn were being evacuated on foot to the rec center, which is to the north (not shown in my image as it's new. Currently sits on area of those tennis courts). So they would have been traversing the floodway to get to safety.

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This is not "hard to say". Its very easy to say based on all information available that the cabins that lost girls were 100% well above the 100 year BFEs and also likely above the 500 year BFEs.

sellthefarm said:

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Teslag said:

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Possibly, hard to say without the supporting exhibits which cabins were included in the LOMR determination. One thing to point out is that I think I saw that those in Bubble Inn were being evacuated on foot to the rec center, which is to the north (not shown in my image as it's new. Currently sits on area of those tennis courts). So they would have been traversing the floodway to get to safety.

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This is not "hard to say". Its very easy to say based on all information available that the cabins that lost girls were 100% well above the 100 year BFEs and also likely above the 500 year BFEs.

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This is incorrect. Both the Twins and Bubble Inn were within the boundary' of the Zone AE floodplain

Twins = yellow
Bubble Inn = red

WBBQ74 said:

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Alta said:

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Ok - I'm no mathematician but if that's the the risk of being flooded (which can mean inches of water and not full of water) then the risk would be something like .2% divided by 5 (cabins are only occupied about 70 days a year) divided by 2.5 (these girls are not in the cabin that much. My guess is we all do things on a daily basis with our kids that are much riskier than where this cabin was situated.

Just a horrendous accident.

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The 100 year flood areas mean that there is a 1% chance of the water surface elevation being that high. The Zone AE black lines show 1840' and 1835' in the floodway, meaning that the 100 year water surface elevation varies between those 2 elevations as the water runs downstream.

The 500 year flood areas mean that there is a 0.2% chance of the same, but the FIRM maps don't show the corresponding water surface elevations. They are obviously higher. How much? Guessing here, maybe a foot or two higher or so. The HEC-RAS model done back in 2011 would have included these computations. It's all theoretical until it really happens.

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The 500 year does have corresponding water surface elevations. They just don't show up on the map. You have to look at the FIS profiles for Kerr County. I checked and in this location the 500 year is approx. 8' higher than the 100. I was surprised by this because it's usually much closer than that. But then again this is a narrow channel.