Why Houston Keeps Flooding; Meet Photo Blog Purple Time Space Swamp


Photo of I-45: Marc Longoria via Swamplot Flickr Pool


37 Comment

  • Apparently Purple Time Space Swamp was in my ‘hood yesterday.

  • The chron editorial and marketplace article really nail it.

    Houston mayors and council members like Brenda Starsig do the bidding of developers who give them campaign funds and who knows what under the table.

  • The good news is the data from the gauges on the streams are generating data that support the updated floodplain maps from the last 10 years.

    Large parts of the flooding are areas that are expected to flood in a 100-year and 500-year storms. The reality is life played out like the models predicted because they received 100-yr and 500-yr storms.

    Also, no flood reduction project will completely eliminate the floodplain and move it to within channel banks if they are out right now. It is cheaper to buyout homeowners and remove the residents from the floodplain all together.

    In addition, the amount of the rainfall also means there was structural flooding unrelated to riverine flooding. Again, the shear volume of rainfall will not get mitigated due to the extreme costs.

    Also remember, the metro is a huge area. All major flood events occur differently. Your area may fair good in this event and the next get hit. This means really dumb statements like “I didn’t flood in Allison” don’t mean anything. Allison flooded a smaller and different areas than this storm. Confluence areas (downtown) will always be targeted.

  • Houston floods because (a) it is more or less flat; (b) it rains, sometimes a lot at once; and (c) it is an urban area, with a lot of impervious surface, for better or worse. Let’s not overthink this folks.

  • Al, your statement is completely ignorant. Houston floods because developers don’t build detention anywhere. Corrupt council members and mayors allow them to build sky scrapers where previously there were only small strip centers. Developers raid TIRZ infrastructure funds for subsidies and leave them broke for drainage projects. Areas that never flooded started flooding in 2009, 2015 and 2016. We have had a 100 year flood and 500 year flood 11 months apart.

    While your statement is completely ignorant, it’s important to address this and educate the masses.

  • Flooding, calling someone stupid is no way to prove your point. Besides, why are you so hell bent on blaming someone for the fact that water accumulated in an area with nowhere to go….. Like it’s been doing for millions of years all over the world.

  • Flooding,

    Developers do build detention.

    What we don’t do is force redevelopment to retroactively build detention for areas that was paved prior to development (i.e. Industrial site turns into commercial development). That is a little harder to implement because it may run a foul of some property rights issues and will lose in court.

    Regional detention is more effective than smaller onsite detention. An oddly enough, onsite detention can make some areas worse for flooding instead of better.

    Hopefully a large buyout of some of the flooded areas occurs leaving areas primed for regional storage.

    P.S. Regional storage also adds potential for parks and nature areas.

  • I wonder if any developments have looked into using porous asphalt. Seems like especially in lower density areas/strip malls/parking lots, that this could help mitigate some of the flooding.


  • I don’t understand the Houston Press’s insinuation that the delays in the repairs on the Barker and Addicks dams have somehow contributed to the flooding on Brays Bayou. First, those dams discharge into Buffalo Bayou, not Brays Bayou. Second, it is my understanding that these repairs will do nothing to increase the protective qualities or capacity of these dams, but are necessary to ensure that there is not a catastrophic failure.

  • My, my, Flooding, let’s take a deep breath or three. My observation only noted why Houston is prone to flooding, not that flooding was a great thing, or even inevitable. The local residents can’t do much about the first two factors that were noted, but there are a whole lot of decisions that can be made about the third factor to minimize and moderate the situation. There are financial and political costs, but by all means, go for it! “Be the change you wish to see in the world”, or whatever that bumper sticker says.

  • @Flooding

    Your statement may be the ignorant one. The amount of impervious coverage has nothing to do with how tall the building is. A strip center and skyscaper could have the same amount of impervious coverage. Also, it is very possible that a skyscraper could have less impervious coverage than a strip center because building up means you have to do less building out and you could replace acres of impervious parking with plazas, rainwater retention/filtration, etc… “Educate the masses”

  • If you’re receiving 100-yr floods a couple times a decade wouldn’t that mean you’re using an obsolete data set that needs to be more predicative with revised trend lines? Meteorology is a dynamic field with subtle changes to historical/prevailing weather patterns occuring on a constant basis. My concern is if our floodplains, insurance rates and flood retention plans are all based on 100yr floods that are occurring every 10yrs then how in the world can we expect to have adequate protection against a true 500yr flood, both physically and financially?

  • “We have a history of failing to leverage boom-time prosperity to improve land-use regulation and infrastructure planning to solve these problems. Then, when busts come, we say our hands are tied because we need growth at any price. This is foolish, and I think stems partly from Houston’s historic sense of inferiority, the mindset that we somehow are not good enough to have a better quality of life. Dallas-Fort Worth and Austin have stronger planning and regulation, and they seem to be doing just fine.”

    Last part seems aimed directly at Tory Gattis.

  • Is “JJ” Jason Johnson whose family owns Memorial City mall?

    When you elevate a property, everything runs off. These parking lots from the 1950’s you are replacing retained tons of water. You are replacing them with elevated commercial properties that hold zero water and push everything off the property onto surrounding neighborhoods.

  • “Corrupt council members and mayors allow them to build sky scrapers where previously there were only small strip centers.”

    No stardig fan here, but you do realize that a sky scraper, while tall, wont have much more of a footprint than say a strip center. Thus the impervious coverage changes little between the two.

    “Areas that never flooded started flooding in 2009, 2015 and 2016. We have had a 100 year flood and 500 year flood 11 months apart.”

    I dont even know where to start with these sentences. But your issue is with the Feds that labeled the 100 year and 500 year flood plains, along with flood ways.

  • Looks like all the developers are on here trying to deflect blame and spreading the same lies they staple to their campaign checks. Metro National, Fidelis, and Klotz engineering are big time perpetrators of flooding.

    Fact: if a major commercial property is elevated, it will flood other properties. Fact: lots of undeveloped acreage was also developed and concreted over without adding adequate detention.

  • Guys, the skyscrapers plus parking garages and retail and everything else take up much more space than the previous developments. You folks (and “JJ”) are grasping at straws to defend unconscionable actions.

  • Flooding, why would a 3 acre strip center be better for flooding then a highrise with a 3 acre footprint? As pointed out, sometimes building up requires less footprint so you could replace a 3 acre strip center with a 2 acre building that has 1 acre of green space.
    And I’m all in favor of laws that would require new flood mitigation built when building on land that was previously porus (not sure the term). But I don’t think that someone rebuilding over existing nonporus land should have to do anything extra.
    (PS: Before you ask, I’m not part of the developer cabal and receive no funds from said cabal)

  • What’s going to be really disturbing is if these 100 or 500 yr floods keep coming once or twice a year every year…

  • Shun the non-believer….shun!

  • Cody – the issue is all the new development is elevated. It’s infuriating to see neighborhoods under water and brand new construction with dry parking lots as far as the eye can see. Don’t get distracted with the skyscraper comment. It could be a skyscraper or grocery store. If they are elevating and putting in comparable detention for every elevated acre, that causes flooding. And, guess what, developers don’t put in that offsetting detention. A dilapidated 1950 parking lot will hold a hell of a lot more water than a brand new hotel or grocery store or large office building.

    Cody, does that make sense?

  • Addicts and Barker reservoirs are working precisely as intended this week. The development around them . . . less so. As of a few minutes ago, there are over 74000 acre-feet of water in there (something like 2.4×10^10 gallons) just waiting either to slowly trickle down the bayou, or burst through the dam and really cause some headlines.

    As was pointed out, more and better retention ponds are needed. Two 500-year floods in 11 months would suggest this problem is not going away or was not properly understood at the outset. Or we can continue to pave over everything and then just . . . something.

    However, there does seem to be some forward thinking up on 99 north of I-10 in Katy though so maybe all is not lost. There is a lot of flood control-looking landscape there but I have exactly zero knowledge of the spacial and temporal capacity of said structures.

  • @Joel It’s not as improbable as you might think to get hit by a 100 year flood 2 times in 10 years. Let’s do the math. 10 year flood means you have a 1% chance of getting hit by a flood in any given year. With 10 trials the chance of not flooding is defined by (1-0.01)^10. Or about 90%. So 10% chance of flooding 1 or more times. To test for 2+ times you have to do a Binomial distribution. Luckily Excel has a function for that and I’m bored. For 0 times it’s about 90%, for 1 time it’s about 9%. So 2 or more 100 year floods is about 1%.
    Now here’s where it gets fun. Let’s treat the last century as a series of 10 year events. In each of those 10 10 year events there is a 1% chance of 2 100 year floods. what’s the chance of seeing that happen once in a century? Well, lucky for us we already did the math! It’s 10%!
    Anyways. It’s unlikely, but not impossible. 100 year flood math is fun.

  • I think what Flooding is trying to say is that finish floor levels and natural grade in new construction are raised *a lot* due to flood control regulations. Developers are supposed to mitigate this effect with stormwater retention, to varying degrees of success. So the new project creates an ‘island’ in a sea of existing development. Over time, more and more new projects create dams and alter floodplain drainage. In Bellaire there was a lot of issues with new homes being built on raised pads, and changing the whole watershed for the worse.

  • Phil is right. Remember that Houston has to deal with two kinds of flooding: sheet and riverine. When you swap out a steel mill for a shopping center or apartments, you probably change little of the amount of impervious cover. But you definitely do affect the flow of water over the site and exacerbate sheet flooding. The only way to mitigate that is to do detention onsite. A big regional detention pond a few miles away is not going to do much to mitigate sheet flooding from redevelopment. Regional detention does help keep the bayous from overflowing, but the water still has to get to the drainage system. When you build up lot after lot after lot and create a damming effect, you exacerbate sheet flooding.

    There is nothing preventing the City from requiring detention for redevelopment of existing properties that do not increase impervious cover. Chap 245 of the Tex Local Government Code specifically exempts regulation to prevent flooding in a flood plain. There is no taking as the developer can do underground detention if they do not want to dedicate any land. Yes, it would slow development by raising the cost. But right now, developers have been able to get a free ride on the externalities of the increased flooding caused by development. We cannot keep making residents take one for the developers’ team every time it floods.

  • @ Flooding:
    The caricature of the greedy and corrupt developer is nonsense. Land in Houston isn’t cheap anymore, especially in the inner city. If forced to install underground detention when redeveloping property, the project will almost always be dropped. It’s not feasible to buy at a premium, excavate, cover, and build on whatever is left after all of the government agencies have signed off on everything. So no new detention gets installed and commercial developers go out to the suburbs where land is relatively cheap.

  • Completely MHO and YMMV but I lay the 249-adjacent flooding this week squarely at the feet of all the development out there — i.e.,, the Vintage and adjacent retail was not there during Allison — those neighborhoods did OK because there was significant forestry still in place. Now it’s a sea of concrete.

  • @ MrEction: Now apply your finding that the odds are 10% of two 100-year flood events occurring within a 10-year bracket to each and every single watershed in the Houston region. How many watersheds is that, exactly?
    Going clockwise off the San Jacinto River part of the ship channel, there’s Vince, Sims, Brays, Keegans, Buffalo, White Oak, Little White Oak, Hunting, Halls, and Greens bayous, Cypress Creek, Spring Creek, the North & South Forks of the San Jacinto River, Peach Creek, and Goose Creek. Further south there’s the Clear Creek watershed, Dickinson Bayou, the Brazos River and Oyster Creek. I’m probably leaving out a bunch of tributaries that also pose flood risks and I know that I’m leaving out other streams that flow mostly through the countryside or into marshy areas, but that’s 20 big watersheds impacting urbanized development.
    If any two of those (at least) 20 watersheds has a 100-year flood event within a ten year span then it could accurately be said that the Houston area has suffered multiple 100-year flood events within ten years…but that would be misleading. It would also be misleading if I were to imply that each of the watersheds flood independently of the others, however; they are certainly interrelated.
    The fact is, the science is set up in order to analyze risk to small finite increments of land area, not to reflect on an urbanized region as a whole. Furthermore, as kjb434 noted, the science appears valid.

  • Shmoo – Ft Bend county has developer rules in effect and it has not hurt their development. The reality is compliance with gov rules does not shield developers from a civil duty to prevent flooding out their neighbors and they should plan the projects accordingly and purchase lots of land factoring in the true costs

  • I think we can all agree that the Bayous being overtaxed is the most direct source of the flooding. So it seems to me the most logical question to ask is: Why are the Bayous exceeding capacity? From reading the previous comments, I think we can all agree that the total amount of runoff being dumped into the Bayous doesn’t change with re-development since the amount of impervious area does not change.

    So, obviously we need to look at new development that’s covering over previously permeable areas. That could the result of many different types of projects: 1) Large subdivision projects by production builders, 2) Large multi-family developments inside or outside the loop (example being the large Camden project built on what was a very large patch of grass in Midtown). 3) Mid-sized developments new gated communities of dozen+ homes, mostly inside the loop which have their own driveways, 4) The many smaller town home developers doing 2-4 houses at a time.

    Since much of the development inside the loop is done over existing impermeable surfaces, it would seem to me that the majority of the additional demand on our Bayous is coming from the large greenfield production builders further upstream. My intuition is that the amount of building going on out there most likely dwarfs what’s occurring inside the loop (can anyone find numbers on this?). And what’s really fueling all that development is the billions of Federal, State, and Local tax dollars going to expanding and enlarging highway construction all over the place. By reducing the time/cost of commute, they serve as enormous incentives enabling building and selling more cheap houses further away from the employment centers closer to the city. In a nutshell, that is the sprawl of Houston is famous for and I think the main source of our flooding woes.

    There’s no easy answer since we all want cheaper houses but someone pays for that somewhere. There would have to be a REGIONAL initiative to stop subsidizing cheap housing out in the suburbs to help prevent the flooding of communities downstream. The answer is MORE DENSITY inside the city. But that would mean state or federal level intervention to encourage more development in existing impervious areas, and that is not likely to happen anytime soon if ever.

  • @ Smoo & Flooding: Any additional burden placed on the development of raw land will in the short run be factored into the bid price for that land. So that means that landowners eat the costs. Initially. Over time, that should impact the supply of developable land in terms of its highest and best use, and that would cause housing prices to rise as a function of supply and demand until the cost has been passed-through to the consumer. If the base cost of housing is higher then a portion of the market for new homes is simply cut out due to affordability; this may be offset by additional development of other types of lower-cost and/or lower-impact housing. That means that incumbent homeowners would actually stand to gain, whereas renters or new entrants to the community would be hurt badly. That is very regressive policy, but also it is not clear that it would resolve many of the legacy problems that already exist, some of which have to do with subsidence.

    If regulations are not effectively regional in scope and do not effectively address grandfathered properties, then its possible that strict regulations inside of Houston could push development to less-regulated areas further up the watersheds that impact Houston, which could actually be counterproductive. Taking that into consideration, there’s a good argument to be made simply for taxing all property owners and using that to improve flood control by a variety of means, ranging from ditch maintenance to regional flood control basins to condemnation of frequently-flooded properties. If that sounds like a familiar strategy set…well yeah, it is. Houston as a region has not had its head up its ass about addressing these problems except in terms of financing. But the solutions and policy issues appear to be well-understood.

  • @Niche: Nothing is more regressive than letting developers avoid the cost of proper drainage/flood mitigation that results in flooding for regular homeowners and renters. I think anyone in the Greenspoint apartment complex that got flooded out would be happy to pay a few more bucks a month to be free of floods. Same for the homeowners in Meyerland who have been hit with flooding twice in less than a year. And the cost of detention is greatly overstated by the developers. They are required to do detention on undeveloped land and it has not resulted in some great affordable housing crisis. While it is true that much of the really cheap land is gone in Houston, the real estate that remains is very reasonably priced compared to most other major metropolitan areas. Requiring a tiny portion of the property to be dedicated to a detention pond will not turn Houston into Manhattan.

  • @ Old School: I’m not saying that there shouldn’t be flood-control policy or that there should not be government interference in this which is a classic example of an externality generated by private markets. Not at all! I want that to be clear.

    The issue is that there are consequences to any set of policies, and we need to bear in mind not only the 1st-order consequences, but the 2nd-, 3rd-, and 4th-order consequences and select the policy approach that does the least harm and reflects a semblance of social justice.

    When I say that, I am not saying in effect: “First do not harm to thy developers.” Because…what’ll happen is that as long as there is demand there will be development and to the extent that it is more difficult to gather entitlements for development, that is also going to narrow the number of developers willing to make a go of it and until their profit margins on each project reflect the added risk and involvement. The developers will be there. They just are. You can hurt some of them, but you can’t just stop them. (This is more a lesson from California than New York IMO, if we’re making comparisons.)

    The developers are just middle-men. The impacts are going to be felt by those that own capital or land, so incumbent property owners, and those who own labor, so workers. Developers merely re-order a combination of land, capital, and labor to transform it. To some extent they also transform policy and to some extent the policy transforms them, but they will always be present in some form. There are two things about policy that you’d want to be careful about with respect to developers. The first is that they need a set of rules to play by that they can understand; this is why the Ashby highrise was so consequential is that it became unclear what was allowed and what was not. The other thing is to be careful about regulatory capture, where developers subvert the political system. One of the solutions about that is to keep the regulatory system limited, manageable, and transparent; another solution (which is related to the first) is to ensure that the playing field is wide open so that there is no local cabal of developers which can pull the strings and engage in anti-competitive behavior.

    Now…I say that and I say this. Where anti-competitive behavior is concerned, it can and more often does occur with the long-term holders of land and capital (that’s you Old School) than with the middlemen who hold it momentarily to transform it. *THIS* more than anything is the lesson of California.

    Mind you, I am not saying that flood control policy and that alone will cause the problems in Houston that now plague the San Francisco Bay Area. *Not saying that.* However, there are many types of policies that overlap and are implemented and that have ramifications over a very very long time horizon and yes we should be cognizant and mindful of that.

  • @Niche Sadly that problem becomes immensely more complicated because you can’t treat each watershed as a truly independent variable. The all co-vary significantly since they are hit by the same weather patterns and may share some downstream drainage (not sure of that). So you can’t really look at it that way at all. It’s more that you would have to look at the entire city at once.
    Don’t get me wrong, 100 year flood plains are a fairly crude statistical tool, but I don’t think they’re as far out of whack as some people think they are. At the core of some of those numbers are calculations by actuarial statisticians, and those are some of the best human calculators on the planet. If 100 year flood plains were incredibly wrong then insurance companies would not rely on them as much as they do.

  • @ MrEction: Yes, I acknowledged the covariance problem in the last sentence of the third paragraph. You’re absolutely right that it’d have to be adjusted for in order to develop a valid statistic at the regional level.
    All the same, I brought that up to make the point that these arguments that Houston has had ‘x’ number of 100-year flood events in and around it over the past ‘y’ years do not in and of themselves reveal a problem with the flood maps or that circumstances are necessarily worsening for any specific reason. Furthermore, there are enough different watersheds or watershed clusters (or however else a statistician might approach the region) that it really probably ought to be expected that in any given ten-year span that indeed there will be multiple flood events somewhere or another within the region.

  • We need to think of the whole area as a large retention basin:
    Greater Houston is a reservoir and we are all island property owners within it.
    This Lake needs to have a static capacity to hold X acre-feet of water for Y time…
    So nobody is allowed to push fill-dirt around to increase the size of their yard!

    Even when it’s 97 degrees in August and hasn’t rained for 3 weeks, we still need to see that big dish full of floodwater.

  • @ movocelot: Yeah…but the fill dirt is getting used to build up lots in order to dig down to make streets, open spaces, and of course dedicated detention ponds deeper. That’s actually good policy as far as new development is concerned, it prevents casualty loss in the neighborhood and also downstream.

    Now on the other hand, lets say that you have a lot in an established neighborhood like Meyerland and you start building it up; well first you’d have to bring in fill dirt and that’s going to be quite expensive, but also if the runoff impacts your neighbors then you’re going to be legally liable for that and whether you realize it or not, that’s also going to be expensive. If you want to have a big yard and you’re still concerned about flooding, just build higher on pier-and-beam and put your living area that much higher than the base flood elevation. That is the normal and sane and cost-effective approach, and that’s pretty much it whether you happen to live in a flood-prone area in Bellaire or Tiki Island or in frickin’ Cambodia.