Sand Bags & Flooding: How Effective?

  • Thread starter matthyaouw
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In summary, sandbags are used to create a barrier against flooding, but they are not very effective. If there is no clean out on the main line, then one has to disconnect drainlines to sinks and plug them.
  • #1
matthyaouw
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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.
 
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  • #2
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.
 
  • #3
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.
 
  • #4
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.
 
  • #5
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.
 
  • #6
How do you shut off the sewer line?
 
  • #7
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.
 
  • #8
matthyaouw said:
my house was a couple of inches off flooding the other day

Lucky... :frown:
 
  • #9
Things not so good at your end? :frown:
 
  • #10

1. How do sandbags prevent flooding?

Sandbags are an effective method for preventing flooding because they create a barrier that slows down or blocks the flow of water. The weight and density of the sandbags also make them resistant to being washed away by the floodwaters.

2. How many sandbags do I need to prevent flooding?

The number of sandbags needed to prevent flooding will vary depending on the size and severity of the flood. A general rule of thumb is to have at least 10 sandbags per linear foot of the area you want to protect. However, it is best to consult with local authorities for specific recommendations.

3. How do I properly place and stack sandbags?

Sandbags should be placed directly on top of each other in a staggered pattern, with the open end facing towards the direction of water flow. Each layer should be tightly compacted and reinforced by folding the open end back over the top of the sandbag. It is also important to have a layer of plastic sheeting or tarp between the sandbags and the ground to prevent water from seeping through.

4. How long do sandbags last in preventing flooding?

The lifespan of sandbags in preventing flooding will depend on the quality of the sandbags and the severity of the flood. Generally, sandbags can last up to 6 months in dry conditions, but they may need to be replaced sooner in areas with heavy rainfall or frequent flooding.

5. What should I do with sandbags after the flood?

After the flood, the sandbags should be removed and disposed of properly. If the sandbags were contaminated by floodwaters, they should be disposed of as hazardous waste. If they are still clean, they can be reused for future floods or used as fill material for construction projects.

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