Ensuring the Responsible Management of Montana Floodplains Through Communication, Cooperation, and Education
Stemwall Foundations
When high waters surge and swirl around a home’s foundation, it is critical to keep the slab anchored to the ground. Stem walls protect against uplift by connecting the foundation down into the ground.
Why Stem Walls Work
Stem wall foundations are successful because they are integral. They marry the slab to the foundation and the walls to the slab and stem wall. The pour itself is continuous, which means that it is seamless. As a result there is no seam between the stem wall and the slab. There is no seam where water can enter and weaken the connection between the stem walls below ground and the slab on grade or the walls that are anchored into the slab. A stem wall and integrated slab structure is more likely to maintain its integrity when water surges and winds pull. This type of construction is ideal for areas prone to flooding. When high water comes, it moves around the foundation, unable to get under the slab and lift it up. This type of construction has been found to be more reliable than simply raising the foundation or building on fill .
Resources
Building in a Floodplain
You’ve probably heard applicants say “I’m just moving some dirt around from here to there – I’m not actually bringing in truckloads of fill. What’s the big deal?”
Well, the big deal is that doing this has now created an artificial obstruction. Check your regulatory definitions. If Mother Nature snaps a tree and sends it down the stream where it gets hung up on a gravel bar catching additional debris which eventually backs up the stream enough to flood someone’s house, the resulting flood damages were caused by a natural obstruction. If, on the other hand, someone cuts down several trees which then float downstream and get hung up on a culvert, catching more debris ultimately flooding someone’s home, those damages were cause by an artificial obstruction.
State law denies "natural obstruction" as any rock, tree, gravel, or analogous natural matter that is an obstruction and has been located within the floodplain or floodway by a nonhuman cause.” Now what happens when you design or permit an artificial obstruction which ultimately causes flooding – such as a soft bank stabilization project that unravels during a flood? That’s what litigation is all about. More than likely, the judge will not be too pleased with faulty designs approved by the floodplain administrator that cause flood damages.
Do not take design and permitting decisions lightly. Twenty years from now, perhaps the floodplain administrator and the engineering design firms will be long gone – but property owners and government will still be around dealing with the problems ill-advised engineering designs and permitting decisions may have caused. The attorneys will certainly be here… Check out the Examples
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