Building IN a Flood Plain?

chisueMay 7, 2011

Does anyone here have experience building IN a floor plain?

Our house is on an acre directly west of a narrow but deep-cut water course. It was a creek until it was dredged in the late 1800's. In summer you could cross it without getting your ankles wet, but in spring and winter it can rise to the level of the bridge across it and is a raging torrent. The SE corner of our lot is designated flood plain.

Immediately east across the bridge sits a house that is now on two acres. Over twenty years ago that owner subdivided his lot, creating another acre+ flag lot behind his house, bordering the water course. Most of the flag lot is under water whenever there's a storm. (Neighbor kids kayak the 'lot'. Today that lot could not be sold as a buildable lot.

An unfortunate couple have owned the flooding flag lot for all those years. They've tried to either get a permit to build or to sell the lot -- no dice. Now before our city's Building Review Board is their latest proposal.

They propose to build a two story, 6000 sq ft all brick Italianate house that will rest on a five-foot deep brick water-storage foundation. The foundation is designed with vents to allow flood water into the foundation, retain it, then discharge the water as the water course goes down.

Most of us neighbors think this is a bizarre and dangerous idea. I envision the stuff that is in the water when it is in flood stage (tree limbs, animal remains, plastic, glass, etc.) smashing into this foundation, creating a dam against it, resulting in flooding upstream -- and breaking the foundation itself.

I've never seen such a design. Have you?

I don't oppose "A House" on the property. Something on stilts could be quite striking and allow water to flow freely underneath. Such a house would work with the existing site. This design seeks to alter the site (and the water course) to build a completely incongruous design. I'm very afraid this will get built and we'll ALL be sorry.

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Make sure you can even build in the flood plain.

FEMA has rules about elevation above the flood plain to purchase flood insurance, especially on new construction.

    Bookmark   May 8, 2011 at 2:40PM
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My parents have purchased property where part of it is in the flood plain...they are not able to build or even "touch" any area in the flood plain. (100 year flood plain) Fortunately for them they have enough property to build elsewhere without touching the flood plain.

I second brickeyee's suggestion, they may not be able to build in the flood plain at all.

    Bookmark   May 8, 2011 at 3:33PM
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We couldn't build on the portion of our lot that's in the 100-year flood plain either.

However, our city engineer says he has to OK this plan. The lot owner says FEMA has "conditionally" approved it. I get the idea that FEMA won't condemn it until it's built and proven to fail!

I posted hoping someone here had knowlege of this sort of 'retention foundation' -- hoped someone knew places it has *failed*, or why it's not appropriate in this situation.

All that stands between a permit for this weird thing now is the Building Review Board -- and citizen outcry.

At the last BRB meeting (May 4), staff said they could require the lot owner to legally assume responsibility for damages arising out of this construction. Well and good until there ARE damages and a dozen homeowners up and downstream sue for tens of millions.

BTW, the lot owner isn't in a hardship situation. He bought a $4M showpiece home in town about eight years ago. I can't see a bank issuing a mortgage for this, but he probably can pay cash.

I don't really believe the lot owner wants anything except to get rid of his worthless lot -- to stop paying RE tax on it. I don't see the couple living in this place. They are about sixty; children grown. (How would they ever SELL it?)

    Bookmark   May 8, 2011 at 5:13PM
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We built in a flood plain. Our 3/4 acre lot is about a half mile from a major river. We were required to bring in enough dirt to get it out of the 100 yr flood plain so that we didn't have to carry flood insurance. We added another 6 inches of dirt above the 100 yr flood line. The dirt costs were high -- around 45K. But absolutely no water issues -- in fact, we don't even have a sump hole. The soil here is mostly sand which drains well and we are so high up that we've had major rains and flooding around us, but no in our lower level.

    Bookmark   May 11, 2011 at 11:30AM
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shelly_k -- That's pretty amazing! Here, you cannot do that. You can't *alter* the plain. If a lot of people did what you did, lower areas would flood; the water has to go somewhere. We couldn't even distribute dirt from excavating our crawls on the portion of our house that's in 100-year flood plain. The dirt had to be trucked away.

    Bookmark   May 11, 2011 at 12:24PM
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The owners of the lot should donate the lot to the town as conservation land and take whatever tax write-off they can. If I was the neighbor in front of this flag lot it might be worth it to pay a small/reasonable price to add this lot to my lot. Of course, not such a good deal for the current lot owners!

    Bookmark   May 11, 2011 at 12:53PM
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I wouldn't think any responsible insurance company would insure a home built like that in a flood plain. I certainly hope not since the rest of us would foot the bill in case of disaster. And that sounds like a disaster waiting to happen!

    Bookmark   May 14, 2011 at 6:29PM
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I have to say - I really don't think a 3000 ft structure placed on a 40k+ sq ft lot is going to alter the flow of water significantly. You are not going to flood nearby previously safe houses. Things could be done to improve the flow of water in the lot to compensate for the small potential daming effect.

That being said, it would seem unlikely that this would ever get approved but these things seems to be up to local interpretation.

I am building in a flood plain (on pilings) and the rules are sometimes a bit extreme. There is no way something like this would be allowed down here. Nor would bringing in dirt to alter flood plains - that is unbelievable. Our jurisdiction requires better protection than the federal flood insurance program. Obviously this house is unlikely to qualify for federal flood insurance.

    Bookmark   May 15, 2011 at 6:24AM
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Thanks, all. The point about being UNABLE to INSURE it may put 'end' to the project. Requiring the owner to cover any damages due to his construction may prove an impossibility. (He could also sue, saying that is an unreasonable burden. Ugg.)

chispa -- Yes, I have hopes that the donation/tax relief idea will win out here. Some days I feel like calling the guy's bluff and saying, "Sure, here's your permit. It's contingent on you actually building the thing, insuring it, and living in it for X years. You can do that or donate the lot."

David -- How difficult is it for you to insure your house on stilts? (BTW, some of this 'lot' is ALWAYS under water except in a drought.)

    Bookmark   May 15, 2011 at 11:49AM
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There is a ton of misinformation in this thread.

If you community participates in the National Flood Insurance Program (NFIP), the community will have a floodplain development ordinance. You need to read this ordinance, I am sure your building department is the one that enforces it and issues permits for construction in the floodplain. And no, FEMA does not prevent construction in the floodplain.

If your community participates in the NFIP, and you build in compliance with this ordinance, you will be able to easily obtain flood insurance.

Now then, the wisdom of doing so, I will choose not to interject my opinion.

    Bookmark   May 19, 2011 at 1:28PM
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KCMO KEN is correct. We are in the process of building a home on the coast in NJ and the regs are controlled mainly by the local town. We were lucky that the rules are some what easier if you had an existing home and are replacing it rather than starting with a vacant lot. I will say it is a major p.i.a. We are the gc on the home and it does take time. Thankfully it is our second home so time is not an issue

    Bookmark   May 19, 2011 at 4:03PM
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