Flood Control

[jenkinstod]

I'm new to this forum, so before I post details on my question, I wanted to find out if this is the right place to be asking it.

Basically, I wanted input on an idea my brother is exploring to minimize impact from recurring flooding at his house. We think the longer term solution is better runoff management, but in the interim, he doesn't feel like he has any choice except to modify his property/house to keep the water out.

The idea is to build a concrete wall around the back perimeter of his house. The property slopes down to a creek in the back, and when the flooding has occurred, it has entered his house along the back wall, entering the two doors into his basement. The idea of the wall is essentially to create a barrier to prevent the water from reaching that wall.

Anyway, I can provide more details, including sketches, if needed and if this is the best place to ask this sort of question. Thanks in advance for any tips or recommendations.

 

[ACtrafficengr]

You are right that runoff management upstream is the bet solution. Unfortunately, that is unlikely to happen. if you are in a built-up area, the best you can hope for is it won't get worse. In rural areas, there are fewer restrictions, so it is likely to get worse.

I suspect that your wall could cause more problems than solution. If water ever gets over it, it will trap the water behind it rather than letting it run off. Also, you could make things worse for your downstream neightbors. Since the wall will contrict the flow of water, it will increase the speed, causing more erosion.

You would probably need permits from your states environmental protection agency and the Corps of Engineers to build anything like that within the streams flood zone. I suspect they might deny your application.

The best solution may be for your brother to give up the walk-out basement, remove the doors and fill in the gaps in the basement walls.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[jenkinstod]

Thanks much for the response. Couple of additional thoughts on the subject.

I agree with the idea that the wall will trap water in as well as it does keeping it out, so he would need some sort of plan to remove the water if this happens. I suppose a portable sump pump might help, plus possibly a pit to place it in if the situation arises.

Regarding the other potential consequences, I'm thinking the impacts would be pretty small. The overall area affected is pretty large relative to the wall he'd be building. It would only be around 40' long, and would be probably 50+ feet from the stream. I'm not sure how deep the wall would be (i.e., distance from house), but I'm thinking it would simply enclose an area that is now covered with a concrete pad, maybe 20-25 feet deep. So overall, we're only talking about a space roughly 20x40'.

Again, I appreciate the comments, and this is just what I'm hoping to get from this forum; potential pitfalls of the idea. If you or anyone else has any other comments, please share them.

Thanks.

 

[sam74]

How long has this been going on and is it a new problem and is his house newly constructed?

Has there been upstream development that might have increased the runoff volume? There could be a potential lawsuit if this might be an issue.

Is the stream a FEMA studied stream? You can look up quadrangle maps on the internet and determine the stream name at this website

http://msrmaps.com/Default.aspx

Then go to the FEMA website here

http://msc.fema.gov/webapp/wcs/stor...&categoryId=12001&langId=-1&userType=G&type=1

and determine if it is a studied stream. If it is this could possibly have some impact on what you can or cannot do.

 

[bimr]

Not so fast.

"Regarding the other potential consequences, I'm thinking the impacts would be pretty small."

Flood control is not that simple. If you put a wall up to stop the flooding, the water is going to seep underground and push up the concrete floor with hydrostatic pressure.

FEMA has a requirement that you should allow flood water to enter the house. That is because the concrete floor and walls are not designed to resist the hydrostatic force of water and you may end up with a larger structural problem than just flooding.

I agree with ACtrafficengr. Your wall could cause more problems than you have with the flooding. The best solution may be for your brother to accept the periodic basement flooding as it comes with the territory.

 

[jenkinstod]

Thanks for both of the responses. A few follow-up comments related to each:

sam74: I'm not sure of the age of the home, but it's not new construction. Although the creek has flooded in the past, it was not this significant. Over the last couple of years, however, there have been several significant flooding events, resulting in significant interior flooding and damage in the house.

Yes, there has been development in the area, and we believe thsi is the primary cause of the increased frequency and intensity of the flooding. A relatively large housing development was completed in the last couple of years, and we believe that runoff from this development, coupled with incomplete stormwater runoff improvement activities, is causing the flooding problem.

A lawsuit is definitely an option, and my brother has contacted an attorney or two. Unfortunately, money is tight, and we're concerned about investing a large amount in legal fees without a very good chance of success. We would welcome any tips or advice on approaching the legal option (especially when money is tight), since I am absolutely convinced that the development in the area is causing this problem. I'd love to have a reputable engineering or environmental firm (or maybe a university?) study this situation and convince the developer or local city/county that they need to take action.

bimr: Thanks for highlighting other potential consequences of the wall concept. I had not considered the potential impact due to hydrostatic pressure, and was certainly unaware of the FEMA requirements. This is a really tough situation, though, since my brother had made some pretty big improvements in the basement of their house, and really need the space for his growing family. Is there a reference you can proved to the applicable FEMA requirement? My brother has obtained quotes from a few contractors for constructing the wall, and none of them have mentioned any potential issues, so I just want to better understand the rules.

Again, thanks to all for your comments. Each exchange on this forum is increasing my knowledge and awareness of the situation, and will help us make a more informed decision.

Thanks.

 

[sam74]

When I was an intern I worked on several drainage related lawsuits. I'm not sure of the arrangement the attorney and client had though. Did the attorney you contacted require fees up front? I would think if he thought it was worthwhile he would take the case for a percentage of the judgement. In any case be sure to document all flooding events with dated video/photos and keep a running tab on damages incurred.

 

[francesca]

... and it wouldn't hurt to keep the rainfall data. Although I think you can get this from NOAA's website, but bonus points if CoCoRaHS has local data.

http://www.cocorahs.org/

 

[Ryb01]

The flood conditions that you've witnessed may have not been the worst to come. Depending on your location, and rainfall event, I would suspect a storm similar in magnitude or even larger 100-year 24 hour storm has not been witnessed in your area.

I agree with francesa, obtaining any rainfall data you come across will be beneficial down the road. There's also some additional data that may be useful to obtain; 1) Historical rainfall events for your region, 2) Floodplain mapping of the creek (is there is any), 3) Local municipal engineering standards 4) Depending on the age of the home, any permits that were required to build the house

Before seeking legal council I would recommend setting up a meeting with your local municipality to discuss this issue.

Hope this helps.

 

[ACtrafficengr]

"A relatively large housing development was completed in the last couple of years..."

Assuming you are in the US, the Clean Water Act requires developments larger than one acre (5 acres until a few years ago) to have a Stormwater Pollution Prevention Plan (SWPPP, pronounced "swip").

If the development meets the minimum size for a SWPPP, go to your municipal planning department and ask to see the SWPPP for the development. In NY, at least, it is a public document available for inspection for whomever is interested, as are maintenance logs. Ask if stormwater controls were installed and maintained as per the plan. If not, you probably have a pretty good legal case.

There are some things I dislike about stormwater laws. However, this is own of the situations they were intended to prevent.



"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[bimr]

You can look through the FEMA 480 publication titled "Floodplain Management Requirements" Study GUide and Desk Reference

http://www.fema.gov/library/viewRecord.do?id=1443

 

[Rye1]

Be weary of retaining attorneys, you could sink a lot of cash into a "no win" situation. These cases are very difficult to win. Stormwater law varies from state to state, which state are you located?

Robert Billings

http://www.newrivereng.com

 

[cvg]

regardless of if a SWPPP was prepared or followed or not, that may have little impact on the amount of stormwater runoff downstream. These plans are often temporary for construction only and do not handle large storms.

Permanent stormwater management measures should have been constructed by the subdivision and this would (normally) be required by the city or county. However developers sometimes get away with stormwater management plans that are less than effective.

If you are not in a regulated floodplain and you do your construction above the ordinary high water mark, and you don't increase the flood hazard upstream, downstream or on the other side of the stream, you might be able to construct a small floodwall. Go the city and check with them about a permit for the wall. They will fill you in on the regulations.

Useful information for evaluating this would include:

Is the flooding caused by ponding or running water?
How often does it occur and for how long?
Is the stream ephemeral (dry part of the year)?
How far below ground is the groundwater level?
How deep is the water when it reaches your house?
How big is this stream (width, depth at normal and flood stage)?

http://www.floodsmart.gov/floodsmart/

 

[jenkinstod]

Thanks to everyone for the responses. Couple of quick thoughts:

1. I have been collecting rainfall data, from NOAA I think, but had not looked at the .org site shown above. I'll check it out. My brother has also been keeping fairly decent records of the flooding events.

2. Regarding the development, and any SWPPP required, I just know that the city had apparently required the developer to pay an additional fee for the construction of some sort of detention basin or other flood control feature, but that this work has not yet been performed. This seems to to be the most egregious aspect of this issue.

Afraid I don't have answers to the other questions. I am very worried about the possibility of sinking lots of money into a no-win scenario, as mentioned above. The city originally signalled that they were planning to buyout a few of the houses in this area, but now seem to be backing away from this. With spring approaching, it just feels like they have no options except to protect themselves from further flooding and potential damanage.

Again, thanks for all the help. If I come across any further info, I'll provide an update.

 

[sam74]

Where is your location? That is a big question.

I have heard of major lawsuits in the construction phase because you still need to be aware of downstream runoff at any point of time. Golf course in particular.

You can't turn 100 acres of forest into a dirt land and not ignore the possible downstream consequenses in the middle of site build out.

Here extremely locally they require an asbuilt survey after construction is complete. It then has to be certified and stamped by the surveyor and engineer that it was built accurately enough to perform as it was designed. I have never seen one single detention pond that was correct on the first go around. Detention ponds take up valuable space in the developers eye and there is usually very little slop in the design due to that reason.

The town next door doesn't have asbuilt requirements. When one particular developer asked me to change the design I explained that I could not recommend that change and stamp it comfortably but the local gov didn't require an as-built certified survey by me so he could vary my design as he sought fit but it would fall on him instead of me. Not sure what he did but I slept good at night.

 

[msquared48]

You need a mirafi filter fabric lined, and drainrock filled, cutoff trench with a central perf pipe installed on the uphill side of the house, discharging via a hardline from both ends to the area downhill from the residence. Continue the trench around both ends of the residence before hardlining to the discharge points. The trench should end up being a large modified "U" shape. The depth of the trench should be at least as deep as the bottom of your foundation to sufficiently lower the water table.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[cvg]

whoa there, constructing a french drain will probably have no impact on reducing the flooding from the river. If the river floods, the french drain will do absolutely nothing to reduce the flood level against the back door. While it may be a good idea to help reduce groundwater and help drain some storm runoff, it certainly doesn't solve the problem that was presented.

 

[jenkinstod]

I'm not sure if I described the problem clearly enough, but I don't think a french drain would work. The flooding at my brother's house is occuring as a creek backs up and rises until it reaches his house. I can't see how a french drain would function in that environment.

Now, it would certainly be helpful if the development that led to this situation had some sort of massive french drain to better deal with their runoff. Just hope they do something soon.

 

[sam74]

so have you looked up the FEMA website to determine if there is a defined floodplain in this area?

You could give a lot more information because you really don't have anything useful enough posted at all.

Better than a french drain or a wall, the easiest thing to do would be to excavate earth between the house and creek to provide room for more flow. But we don't know if that is legally possible because we don't have enough information. State, county/parish, creek name, and so on would allow us to determine this but after repeated request we don't have that info. So it is kind of a mute point at this time.

Really don't see you as being an engineer in the first place. Go hire someone who is. Don't mean to be rude but I just don't see it.

There is enough information available on the web between google earth, fema, quad maps, and etc. to determine a possible fix for this but there is nothing going on at the moment but a guessing match. It would take a field survey in the long run but we are not anywhere close to being able to tell if that is warranted with what info we have.

Good luck.

 

[cvg]

constructing a channel would likely not help unless you have a drainage outfall somewhere else besides the river. the river would back up into a channel during flood stage. This would create a very deep moat around the house which would eventually still go into the basement. Not an ideal situation. A berm, dike or floodwall could work. River channelization might also help. Upstream improvements might could be effective. To protect yourself in the short term, sounds like you have the right idea.