MEASURING PROGRESS IN CUBIC FEET PER SECOND “Also, over the past 50 years, high-impact building and roadway development have reduced the amount of permeable surface to accept stormwater, increasing flooding and pollution. Stream flow speeds in Houston, for example, have increased from under 5,000 cu ft per second in 1930 to about 27,500 cfs in 2000, says the U.S. Geological Survey. With stream-flow increases come a greater potential for flooding. The actual stream flow from 2001’s Tropical Storm Allison in Houston’s Brays Bayou peaked sharply at about 34,000 cfs, 20 hours from the start of runoff. This compares to a more gradual stream flow in 1915, before development. . . . Allison, which caused $5 billion of damage in Houston, would have been a nonevent even 50 years ago because the natural landscape would have absorbed the water, say sources.” [GreenSource]
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So what he’s basically saying is … Tropical Storm Allison wouldn’t have done any damage, if no one actually lived in Houston. Genius.
If we pack everyone in close, we create too much impervious ground cover, but if we spread out we create too much sprawl. I guess we’re screwed either way, so let’s do both.
I grew up in Braes Heights and as I recall the first time the bayou went out of its banks was in the late 1980s. And each time it has, it has been progressively worse. People who grew up there wouldn’t live there now. Even if you gave them a house. Even if it was on an elevated pier-and-beam which is now mandated. Especially if they had friends or family who went through Allison who returned home and measured the water marks.
We should have responsible development, Bernard, which apparently you don’t agree with. May the next flood flood you wherever you are and wipe out memories which cannot be replaced. Drywall can be replaced. Memories cannot. And most don’t have time to pack up all the memories when the water begins to rise.
Other cities regulate development simply because they know developers for the most part won’t. So responsible development required regulated development. Without the loopholes the developers in this city have always enjoyed. May the next mayor close up all those loopholes. And fire everyone in the planning department who probably will retire very nicely between the city pension and the money they’ve taken under the table all these years.
Bernard,
You have it backwards. If you pack everyone in close, you have less impervious ground cover for the same amount of population. Sprawl creates flooding.
Oh, Bernard, you do hear what you want to hear, don’t you. Perhaps the lesson is, “when developing, it’s wise to take into account natural phenomena like rainfall, and think about where water will go after new structures cover the ground.” Oh, wait, that isn’t reflected in property costs, so it must be irrelevant.
You have it backwards. If you pack everyone in close, you have less impervious ground cover for the same amount of population. Sprawl creates flooding.
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Actually development that is not planned creates flooding. The initial problem along Brays Bayou was the development in West Houston which added to the watershed. It was worsened by the development in the Med Center area which replaced green space with concrete.
The answer is reponsible development. Which in Houston means highly regulated development. Although for many of the watersheds, it may be too late.
Anyone know what role subsidence plays in recent neighborhood flooding?
Hello: engineers?
I understand that the City of Houston no longer takes water by well (so increased pop. density should not increase subsidence…)
But does it anyway?
Outlying counties are also experiencing subsidence and need to get off well-water…
but, my question is:
Has the damage been done and the compaction of the landscape will continue?
In Braes Heights I would suspect it has been significant as well as in the Med Center which are the two areas in the Brays Bayour watershed that have experienced the worst flooding. You can pretty much get an indication of the subsidence just by looking at Buffalo Speedway and North Braeswood between Buffalo Speedway and Stella Link. Both are much lower than the greenbelt along the banks of the bayou. And they didn’t used to be. Not significantly anyway. The people to the south have watched the water go further and further north with each flood and deeper as well. I think during Allison several homes on Glen Arbor, Tartan, and Durness had six feet of water. I know someone who lived on Glen Arbor told me the very first flood was only two feet of water and that was, I think, in the late 1980s. So it’s not just increased volume in the watershed. It’s that plus subsidence. And that is a problem in the Med Center as well. And according to some, building weight doesn’t help the situation. And of course the developers are tearing down 1,500 square foot homes and putting in 3,500 square foot homes. Which may cause even further subsidence. I believe the mandated elevation for the pier and beam is five feet. Which may be one foot too low. And if there is more subsidence, it may be two feet too low.
Not a place I would want to live. Growing up the only flooding we saw was the occasional street flooding that rarely went over the curb. We certainly never saw six feet of water.
I live off Hazard and Richmond, during Allison if we hadn’t been two feet up as an older pier and beam house, we would have flooded.
As it was Hazard became a roaring river, taking out our fences and flooding our pool as it made its way to the SW freeway. Remember how that became a lake?
And of course 288 which simply became part of Brays Bayou. I think one of the problems in Montrose was blocked storm sewers. Which had been a problem in Meyerland for years. Apparently the city only cleans out the storm sewers after a neighborhood floods. Or in the case of Meyerland, floods once too often. Of course also contributing to the problem in Meyerland was the fact there were flood gates no one knew about which they closed as volume in the bayou increased which of course caused the flow to slow and the water to back up and of course turned Meyerland into a lake. So now the Braeswood and Med Center areas flood.
Any way you look at it, the bottom line is the lack of any real planned development in this city has been our undoing.
And still they build. With variances and loopholes. Including those which allow developers to bypass the “greenspace” and “water retention” requirements.
I’m no hydrologist (but I did stay at a Holiday Inn last night) but is it even possible to plan/develop for an Allison type event? And if it was, would it be so expensive as to eliminate our lower cost of housing? It is often assumed that the developer realizes all of the benefits our our lack of oversight in this town. Don’t we monetize a good portion of it as residents?
I don’t think it would have been possible to avoid what happened during Allison but it might have been possible to avoid the scale of flooding and much of it was due to subsidence. Houston for the most part became a lake. When land is lower that the river bank, well, you become New Orleans. And we are risking becoming New Orleans.
At some point the bayous are going to have to be widened but even that may not be enough. It may be necessary to find ways to divert the bayous at certain points into large retention ponds or even lakes. Not that any developer would appreciate acres and acres of land they could make millions off of being turned into lakes.
And no doubt developers would sit on any commission formed to address the problem.
That right there of course would be the problem. As it always has been.
I walked the Rice/Southampton streets this past weekend, and noticed most of the sewer grates were clogged with debris: twigs, leaves, grass clippings, trash. Next weekend I’ll bring gloves and trash bags on my walk, and see what good I can do. I’d encourage everyone else to do the same.
I live near Little Pine Island Bayou, between Beaumont and Sour Lake. Flooding is an issue out here, too, far away from urban development. They’re raising the bridge to our little community again, for the third time in thirty years. During the last really big flood, I watched an amazing amount of trash and debris float by in the flood waters, and imagined trash dams clogging the bayous. What with all the trees downed by Rita and Ike, it’s a hydrological mess. Took ten days to drain what an old-timer told me used to drain in a day.
Ok. Let me address a few things since I do have an engineering background. First, new developments are required to have detention and perform analysis that shows there is no negative impact (ie. flood elevation levels) downstream. That has been a standard component of development since the 80’s. If you want to look at unresponsible development, look at areas that boomed in the 60’s and 70’s. Seen many detention ponds inside the beltway?
With regards to design storms, yes it would be possible to design a system big enough to handle Allison, but it would not be econimcally feasible. Personally, I think the City of Houston’s requirement of a 2-year storm design storm for pipes and roads is not enough. There are other local areas that require a 5-year storm event. Basins and channels (and street ponding calculations) are based on the 100-year event, which yes in the last decade has been surpassed a few times. Allison was closer to a 500-year event, the rains earlier this year on the western side of town were somewhere closer to a 150-year event. These storm events are not absolutes, just statistical probabilties and are the best we have to use as a standard. It is simply not feasible for any city to implement a flood-proof policy – it is too costly to put a 72″ pipe under each road, to have a serieis of box culverts under each boulevard, and build a basin and channel large enough to take care of a 500-year event. No one could afford to live in an area like that after the associated cost of the lot and the resulting taxes for the improvements.
Matt wrote:
You can pretty much get an indication of the subsidence just by looking at Buffalo Speedway and North Braeswood between Buffalo Speedway and Stella Link. Both are much lower than the greenbelt along the banks of the bayou. And they didn’t used to be. Not significantly anyway.
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I’m going to take some exception to that statement. First, I recall the banks of Brays Bayou being elevated back in the 80’s when I lived in the area. Second, if the streets have subsided, then the bayou and its banks will subside as well, there won’t be preferential subsidence on either side. I suspect that at some point, the HCFCD came through and built up the banks in certain places.
So, either…
Houston becomes New Orleans
(with engineering & maintenance to give both localized rain run-off & swollen ‘just passing thru’ bayous space & volume to collect, slow down and thus avoid major flood events,)
OR
Houston becomes Bangladesh.
First, I recall the banks of Brays Bayou being elevated back in the 80’s when I lived in the area. Second, if the streets have subsided, then the bayou and its banks will subside as well, there won’t be preferential subsidence on either side…
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The best indication of the subsidence, without getting into the elevation of the banks, is the flooding itself which is gone further and further north between Stella Link and Buffalo Speedway. I lived there in the 1960s and 1970s. My father lived there through the mid 1980s. And everything north of the bayou is much lower than it was back then. The same cannot be said about the area south of the bayou. Some houses along “the bend” across from Glen Arbor in fact remained “high and dry” even during Allison. While everything else on South Braeswood, along with everything along North Braeswood, found itself underwater. That “bend” is notorious. Water tends to like a straight line. And so right there at Glen Arbor it goes straight into the homes and starts spreading out from there.