Drainage Problems in the Houston Area (Home)
John P. Bridge
Yes, we've been through droughts during the past years, but when it rains in the Houston area, it rains, as folks down along the the Trinity River can tell you, especially after the latest round of flooding. There is not much helping people whose homes happen to be in flood-prone areas, except to feel for them, and I do, but that's not why we're here.
No, I mean to address the people who live above the flood levels who have drainage problems that can be overcome, albeit with a bit of creative effort. To understand why most drainage inadequacies occur in our area, we'll need to focus on topography and home-building methods.
First of all, keep in mind that the Houston area is virtually flat and that it rests not too many feet above sea-level, the sea being where all run-off water must eventually collect.
When housing tracts are developed, streets are cut in lower than adjacent building lots (hopefully), but developers cannot make streets so low that they would have to drain uphill. Therefore, in many of the subdivisions around Southeast Texas, the lots are just high enough above the streets to drain. This is true throughout the Gulf Coast region, from Mexico to Florida.
Water that collects in the streets is channeled into storm drains which eventually empty into culverts, which ultimately flow into the Gulf of Mexico. In some areas, water is channeled into reservoirs, such as the Addix Reservoir in West Houston. In other parts of town, the water flows through bayous and creek beds as it makes its way to the ocean. During periods of heavy rainfall, all of these systems can become overwhelmed, thus slowing the run-off rate from residential lots.
If there is not much slope to a lot, water will rise (sometimes alarmingly) during periods of heavy rain. It takes time for water to run off a lot that is nearly level. The situation is exacerbated when the ground is already saturated with water from previous rains.
Knowing all of this, you would think homebuilders would build up foundations (slabs) so that no amount of rain could produce even temporary water levels that might approach the finished floor level of a house.
You would think that, but in many instances you would be wrong. Here's the problem (disincentive) faced by builders and developers in our area.
As you must have noticed, I suspect there are no hills in our area, despite street names like "West Mount Houston." (Or is it East Mount Houston?) I've spent years wondering where that mountain actually is. I'm still wondering, in fact. I've scanned the horizon from the lofty height of the Ship Channel Bridge, the highest point so far that I've been able to attain in this town. Where is that blasted hill?
In any case, there is a shortage of fill dirt because there is a shortage of hills, i.e., dirt piles. Yeah, can you believe it? Nothing is "dirt" cheap around here, and fill costs big bucks because it has to be hauled in from the Hill Country (where they really have hills) or quarried out of privately owned sanitary fill sites.
And I know some people never think about this, but there is no rock in Houston. Everything that resembles construction sand, gravel, stone, etc. has to be trucked in. Hence, the convoys of gravel trucks on our highways day and night. We can't pour a patio slab without someone's having trucked in tons of material from about a hundred miles away.
Have I digressed again? Probably.
Given the scarcity of fill materials and the fact that it takes time to properly build up a pad for a slab, builders are very reluctant to go beyond minimal requirements. Consequently, most slabs (finished floors) in the area are, in my estimation, much too close to the ground. And since, in many cases, the lots are nearly level, we are faced with the necessity of improvising some method of drainage.
If we find ourselves on a lot that does not have sufficient slope, there is nothing we can do to change it. We cannot, for example, haul in 100 tons of fill and raise our back yard, for that would merely compound the drainage problems of our neighbors, who, if they wouldn't actually threaten us with bodily harm, would certainly sue us in court and win. The only thing left, then, is to improve drainage without changing the overall slope or "pitch" of the lot.
Improved drainage can be accomplished by installing area drains -- if there is enough slope between the back yard and the street to allow the drain pipes to conduct water. It takes a minimum (I say minimum) of one-eighth inch per running foot if the water is to actually drain instead of merely accumulating in the pipe and laying there. And then the water won't really "run." One-quarter inch per running foot is much better.
Too often drain pipes are installed whose diameters are not adequate for the job. If you are installing an area drain, a four inch pipe is the absolute minimum, and a six inch pipe will increase the volume of water that can be conducted by more than 100 percent. Unfortunately, a four inch pipe is about the largest that can be run to the curb. The curb is not usually high enough to accommodate a larger pipe. The answer, then, would be to use twice as many four inch pipes as you might have planned on --- two instead of one, for example.
Another important consideration is the propensity for pipes to become clogged with debris -- leaves, pine needles, grass clippings, etc. I think you can see why small diameter pipe would be a complete waste of time.
For some reason, "clean-outs" are not often incorporated into yard drainage systems, but they should be. If, for example, you're making a long run from the back yard to the street, you could easily end up with 200 feet of pipe with a couple of turns in it (on a city lot, and longer in the country). Why not install an intermediate clean-out, say, every 50 to 75 feet. This will certainly make it easier to "snake" out the pipe should it become clogged.
Clean-outs can be installed using "T" fittings with long sweeps. Don't use the fittings that turn really tight. For each clean-out you'll need the "T," a short piece of vertical pipe, a threaded female adapter and a threaded plug. The plug can be installed at ground level so you can go right over it with the mower. All of these parts will be the same size as the drain line itself. Chances are you'll never have to use the clean-out, but if you do, you'll be oh so happy you spent the few extra dollars on it.
The drains themselves must be installed over catchments or sumps, and the drain grates must be easily removable (and large enough) so you can get your hands down there to clean out blockages. Do not use the small diameter drains that simply mount on the pipe itself. These are not easily removable, and there is not enough room for hands. Additionally, the grates (strainers) on these drains can easily clog with nothing more than grass clippings or a few leaves, rendering them useless. Rain water skims right over the top of them.
When it comes to drain pipe, PVC is the way to go. It's easy to cut and join. However, the Schedule 20 PVC than many landscapers use is not adequate as far as I'm concerned. I would use at least Schedule 30, and there is certainly nothing wrong with using Schedule 40, the pipe normally used for carrying waste (sewage). PVC pipe is relatively cheap. Why not opt for the stuff that will never have to be replaced?
Keep in mind, also, that installing area drains will entail removing soil from the yard (or redistributing it). You might even pile it up and make a real "hill." Whatever you do, you must slope the area where each drain is to be located in order to create a sink effect, similar to how a shower floor is sloped. If you do not do this, water will simply rush past your drain and continue on its course toward your house, which, as far as I know, is still too low to the ground for comfort.
can you do if your lot has so little elevation that it is impossible to install
pipes that will drain to the street? Frankly, I don't know. You
might try to excavate large catchments and fill them with rock (you can surely
sell the dirt you take out), hoping that it will stop raining before they fill
up with water, or
. . . bite the bullet and purchase flood insurance.
Maybe I got a little carried away there. If a storm sewer (a culvert under the street) runs in front of your house, it is possible to get permission to tap into it below the street. This will allow a much greater pitch in the run of the drain pipe. Permission is obtained from whichever department or agency governs the area where you live -- county, city, water district, etc. (yes, government).
Under no condition should you attach your area drains to the waste water system (sewer). This is not only against the law, it also introduces sand and silt into sewage treatment devices along the line. Sand clogs sewer lines, since it is too heavy for lift stations. It's like putting sand in your toilet and trying to flush it out. Most of it remains. Additionally, the waste water system will eventually be overwhelmed by the increased volume. Ultimately, you, your friends and neighbors will bear the expense of repairs and upgrades to the system.
Perhaps the worst aspect of this folly is the possibility (indeed, the probability) of siphoning raw sewage up into your yard during periods of heavy rain. Not a pretty picture, if you know what I mean. P.U.
Certainly, if you're building a new house (having one built), you should make the builder aware that you want your house built "up out of the ground," even though this will cost more. The money, as I think you can see now, will be well spent. Six inches from finished floor to grade (ground level) would be the minimum at any point around the perimeter of the structure. And more, of course, is better.
Finally, people who install drainage systems in Texas are supposed to be licensed by the state, as are people who install irrigation systems. I am no lover of government regulation, but I recommend you employ only licensed contractors to do this work.
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Dateline: Houston, September 10, 2000
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