Sand Bags & Flooding: How Effective?

[matthyaouw]

How much use are sand bags when there is flooding? I mean sand is pretty permeable, so surely the water must get through fairly easily, yet it seems to be standard procedure to block doors with them.

 

[Astronuc]

The sand is in plastic bags or a plastic/polymer barrier is placed over the bags. The objective is to build a temporary wall, and the sand bags simply provide mass with which to form the wall.

But the key is to make the barrier as impermeable to water - i.e. use plastic sheet or plastic bags - as much as possible. It is better than nothing.

Without an impermeable barrier, the sand bags simply slowly the ingress of water, and then one needs a collection system and pump to remove the water as fast as it flows in.

 

[matthyaouw]

That makes sense. I'd been puzzling over that one for a while. I may have to invest in some- my house was a couple of inches off flooding the other day (many weren't so lucky) and there's more rain forcast for the weekend.

 

[hypatia]

My Granny has a older canvas sand bag levy around the back of her property. Its well grown over with grass and even trees. but it still worked just fine last spring when the small river over ran its banks.

 

[Astronuc]

The other thing to remember is that if the house is connected to a sewer service - the connection has to be shutoff because the floodwater will push the sewage back into the house and flood it. Worse than just flooding is being flooded with raw sewage.

 

[chemisttree]

How do you shut off the sewer line?

 

[Astronuc]

Sewer lines don't have valves, so they have to be plugged. Some people just cram towels or something like that in the lines.

In some cases, one could open a clean out (threaded plug) usually located on a T-fitting. My septic line goes through the basement across the ceiling, through an L, drops through a short section to a T with a cleanout. I could remove the plug and insert a long plug to seal it if necessary.

If one does not have a clean out on the main line, then one has to diconnect drainlines to sinks and plug them. Toilets, bathtubs and showers have to be plugged because there is usually no access to the drainline.

I used to do work in commercial plumbing - and I think the plumbing in most houses is poorly designed because of the limited access. Commerical plumbing usually had access panels and pipe chases so that supply and DWV could be accessed.

 

[brewnog]

my house was a couple of inches off flooding the other day

Lucky...

 

[matthyaouw]

Things not so good at your end?

 

[Astronuc]

Sorry to hear about the flooding guys.

Floods force thousands from homes
http://news.bbc.co.uk/2/hi/uk_news/6239828.stm

Sounds like it's been severe up around Wales, Lancashire and Yorkshire, especially around Sheffield to Leeds.

Insurers face £1bn flood claims
http://news.bbc.co.uk/2/hi/business/6254960.stm

"The ABI estimates that 27,000 homes and 5,000 businesses have been hit."