That's right... Thanks...

Unfortunately much of that area is well within the 100 Yr (1.0%) flood plain. The rainfall events that create those floods haven't changed however a LOT of that development occurred before impacts of flooding, especially downstream impacts were fully understood and the regulations regarding mitigation were put in place. Those large ponds along Braes Bayou just outside Beltway 8 were put in to try to help the Meyerland area but there is only so much that can be done. That helps out with rain that falls in Alief, but not rain that falls in Sharpstown.

It also doesn't help that City of Bellaire subsided themselves by continuing to pump groundwater rather than buy surface water from Houston.

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Another interesting stat from yesterday's event:

Averaged 24 hour precipitation across Harris County was 7.75 inches, or approximately 240 billion gallons of water, enough to run Niagara Falls for 88 hours.

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Thanks Chita.

I live south of Waller, very little development in the area, only houses on acreage and pastures. The flooding was well beyond the 500 year floodplain. Ended up with water a few feet away from my house even though I'm hundreds of yards from the 500 year floodplain.

Meanwhile, back on topic.......

1 3/4 inches on the north side of Corpus (Calallen) so far.


For my 2 cents....a huge factor in Hill Country flooding is overgrazing combined with asphalt - the former being a much bigger factor than the latter. Done right, the removal of cedar is good to reduce flooding - provided the manager lets it come back to mid and tall bunchgrasses.

San Bernard river is still rising 1ft higher than historical high. Evacuating low lying homes in East Bernard. HWY60 shut down and they expect HWY 90 to close.

Colorado river is expected to crest 6 ft higher than last year at ~50 ft. HWY 59 likely to close when that happens

I am out in East Bernard today helping my dad get stuff out of his place. The water was about 3' higher in 1998, but the river gauge at 90 wasn't installed until after that, so it was still showing 2005 to be the record. We have about another 2' before its in his house, but it's currently rising 6" per hour. Playing the waiting game sucks.

There has been an army of high school kids and residents going around each neighborhood that sits low, helping people move out ahead of the water. We did the same thing in '98, but it was in the middle of the night. At least we have some daylight to work in this time.

This is an issue of pooling, flow rate, and channelization. Nobody wants 5 or 10 inches of water pooled on their commercial, residential, or even agricultural land, slowly flowing off through natural channels or over the ground surface choked with debris and plant growth which slows flow rates.

We build intentional channels: flood control ditches, and we channelize, widen, and clear out existing ones. We build a network of raised road beds that unintentionally serve channel water to specific locations. We are very proficient at making sure smaller rain events flow off our land rapidly into a drainage that is more than adequately sized to get rid of it to the ocean just as quickly. We've even realized the flaw in this strategy and started building retention pools with outflows that permit the water to flow in at a fast rate, but flow out at a lower fixed rate.

Unfortunately, we've also built a dam system that back floods large areas each time we bridge a creek along a raised roadbed in the low lying area on each side, limiting its flow rate to the volume that can pass under the bridge until the water level trapped behind breaches the road itself.

The problem is that now we have created a system that automatically pushes exceptional rainfall into this same drainage system just as rapidly, but at volumes and flow rates that cause them to spill out of their banks considerably more than they might have 50 or 100 years ago when a much more swampy Houston terrain would hold more of it in pool or slow its flow across the ground with grass and bushes and debris. Now our suburban streets are built lowered to channel all that water away from houses really fast, only to help back up a creek into someone else's houses downstream. It is simply an issue of increased channelization, removal of natural impediments to overland flow, and capture basins, and increased flow rates.

I don't see any easy solution aside from planning more catch area with a mind to further ****** the rate of flow into main natural drainage channels.

Planning this ahead of time, and with predictable results, is a near impossible task. Each time we overdevelop an area that was in a much more pristine natural state and alter the hydrology, the results downstream are unpredictable, except that nearly every time you can be sure that the upstream development attempts to increase their own exceptional rain event flow rate into the main channels, flooding those downstream more easily than in the past. This, despite efforts that probably do descrease the impact of smaller rain events.

Anecdotally, in the past, the area where my grandfather lives in cypress has had more rain, and faster, fall for a longer duration, but he never had 6" of water in his house until several masterplanned communities were built upstream, and modifications to roads and bridges were made downstream along little cypress creek.

Got a UHaul truck over on Ella and College in EB. We are waiting it out.

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16+ inches north of Katy in past 12 hours. The 100-year event in the Houston region is a little less than 13 inches in 24 hours.

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Not exactly sure what the "100 year event in the Houston region" was and maybe I'm comparing apples to grapes here, but Alvin had 43 inches in 24 hours in 1979.

Alvin, TX 1979 Rain event

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That's still a US Record. We definitely don't design to that and we can't without increasing the price of everything by 10 times or more. Harris County 100-year storm ranges from 12.4 inches to 13.5 inches depending on how far you are from the coast for a 24-hour time period. Those numbers change to 10.2 to 11.1 inches of rain for a 12-hour period. So you can see how 17 inches over a 12 hour period is such a big deal. It's about 50% more rain than the 100-year storm.

I agree, you get enough water, the geology and alterations to it matter less and less.

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It just kinda grinds on me when I hear folks say, "this is the second 500 year flood in X years." Well that's not entirely true. Take TS Allison for example. Allison dumped most of its rain inside Beltway8 on the west side between there an downtown. The vast majority of that was inside Loop 610. Yesterday's rain was more focused outside Beltway 8 towards Katy, Hockley, Tomball, and around to the Woodlands. So I'd argue that, No, you have not had 2 500 year floods in X years. Two different areas have each seen 1 500 Year (0.2% chance) floods.

Can someone remind me where the Memorial Day floods in Houston were the worst?

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Excellent point. Harris county has 2,400 miles of channels. During the "massive" memorial day flood, a couple miles of Brays and nearby channels (less than 10 total miles) saw 100-year elevations. Most of the houses that flooded were deep within the 100-year floodplain. Crude math here, but in 2015, about 0.4% of Harris County saw a 100-year flood.

I try to tell people that of the 2,400 miles of channels in Harris County, 24 miles will see a 100-year storm EVERY YEAR on average. 2015 we had less than that. Bunch of years we haven't had any 100-year storms. Weeks like this week and Allison fill in the gaps for the years when we don't have any 100-year storms.

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I try to tell people that of the 2,400 miles of channels in Harris County, 24 miles will see a 100-year storm EVERY YEAR on average. 2015 we had less than that. Bunch of years we haven't had any 100-year storms. Weeks like this week and Allison fill in the gaps for the years when we don't have any 100-year storms.

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I really like that way/method of breaking down the probabilities.

I'm guessing you work in hydrology/hydraulics?

Downtown Houston

Get ready Houston. It's coming in full force again

taking on rain in Cypress again. Mostly light rain, but pockets of big fat raindrops too.

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I try to tell people that of the 2,400 miles of channels in Harris County, 24 miles will see a 100-year storm EVERY YEAR on average. 2015 we had less than that. Bunch of years we haven't had any 100-year storms. Weeks like this week and Allison fill in the gaps for the years when we don't have any 100-year storms.

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I really like that way/method of breaking down the probabilities.

I'm guessing you work in hydrology/hydraulics?

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I plead the 5th.

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Downtown Houston

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That photo really looks photoshopped.

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Downtown Houston

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That photo really looks photoshopped.

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Don't think so. I believe its from this photo story

http://www.houstonpress.com/slideshow/monday-morning-hell-the-flood-in-photos-8334272/38

you may be right, that water line behind spaghetti warehouse just looks incredibly sharp. That and I didn't think that buffalo bayou got that high.

EDIT: Looks like it did

http://www.chron.com/news/houston-texas/houston/article/Scenes-from-downtown-during-Houston-s-Tax-Day-7256027.php#photo-9823810

Really tired of rain.

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Downtown Houston

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I was parked in the back of that Spaghetti Warehouse parking lot just a few weeks ago. Glad I'm not there now!

Here it comes again.

Pouring in Bastrop county. Coming your way Houston.

Its been pouring here in Bulverde Spring branch just north of San Antonio for the better part of 2 and a half hours and the radar has that all heading to Houston! get your air boats ready again

Hopefully things can average out a bit and not go from one extreme to the other and back again. Crazy how 2 weeks ago we were about to sell cows and had to stop planting because of lack of rainfall and soil moisture. Is there such a thing as a normal year?

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Is there such a thing as a normal year?

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I tried to warn you about global warming.
/Al Gore - Internet inventor

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When is this craptastic el nino cycle set to end?

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Out west, we're waiting for it to start. Was supposed to be a wet winter. Had a Christmas blizzard, then pretty much squat since.

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Is there such a thing as a normal year?

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I tried to warn you about global warming.
/Al Gore - Internet inventor

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And don't forget about man bear pig he's super serial about him to