Future rain - future proofing

40701085

Folks,

3rd washed out summer in a row, global warming predictions for less predictable but more intense rain periods for Ireland...I am doing groundworks on the site at the moment and seriously wondering if I should be safeguarding against this. The 1 in 100 storm event doesn't seem to be so unlikely anymore, so I'm wondering if my site will be able to cope with the flash flooding.
It's a decent site, runs uphill behind the house at maybe 1:30 drains ok but not super.
What precautionary groundworks (if any) would you advise?

PS I'm no drainage expert so non-technical advice is great!
Cheers

(sorry mod - meant to put this under construction & planning - can it be moved?)

Kashkai

We are lucky enough to have our house on an incline up from the road which has flooded (up to 18 inches) in the past 2 summers, something which the indigenous locals insist never happened in living memory, so yes the weather is changing for the worse. In addition, we had the house built up higher than normal, i.e. an extra course of blocks so it is higher again that the neighbours houses. Result is our house wasn't even threatened by the flood waters whereas the neighbours houses and gardens (incl. septic tanks) were inundated despite sandbags and a lot of manpower trying to divert the floodwater which to me was akin to King Canute trying to hold back the sea.

So my non teckie advice is to use an extra course of blocks to keep the house (and more importantly the damp proof course) above any possible flood level. If there is a slope to a drainage channel (i.e. ditch), put in lots of land drains to drain the site to the drainage channel. Keep the ditch clear of weeds and dig it out wider and deeper if possible. If possible, don't have your septic tank in a depression that will be the first area to flood. This happened to all our neighbours and not only could they not flush their toilets, but they had raw sewage washing all over their land from flooded septic tanks. As our house was built up higher, we were also able to keep the septic tank access covers above ground level so they didn't get inundated by the flood.

Gonzales

Prosperous Dave wrote: »

We are lucky enough to have our house on an incline up from the road which has flooded (up to 18 inches) in the past 2 summers, something which the indigenous locals insist never happened in living memory, so yes the weather is changing for the worse. In addition, we had the house built up higher than normal, i.e. an extra course of blocks so it is higher again that the neighbours houses. Result is our house wasn't even threatened by the flood waters whereas the neighbours houses and gardens (incl. septic tanks) were inundated despite sandbags and a lot of manpower trying to divert the floodwater which to me was akin to King Canute trying to hold back the sea.

So my non teckie advice is to use an extra course of blocks to keep the house (and more importantly the damp proof course) above any possible flood level. If there is a slope to a drainage channel (i.e. ditch), put in lots of land drains to drain the site to the drainage channel. Keep the ditch clear of weeds and dig it out wider and deeper if possible. If possible, don't have your septic tank in a depression that will be the first area to flood. This happened to all our neighbours and not only could they not flush their toilets, but they had raw sewage washing all over their land from flooded septic tanks. As our house was built up higher, we were also able to keep the septic tank access covers above ground level so they didn't get inundated by the flood.

Sounds like the flooding in your area only started after your house was built...Hmmm:rolleyes:

Kashkai

:D

I wouldn't disagree as the build was definitely cursed from start to finish so the bad luck might be affecting the whole neighbourhood now

jack of all

As suggested if you can at all it is wise to widen any onsite ditches, if possible increase the size and depth of any site constructed soakaways to create some attentuation. Limit the use of non permeable paving around the house and driveways- these will contribute to flash flooding as surface water will not be able to permeate to the ground below- use gravel, open jointed paving or other suitable paving materials to achieve "sustainable urban drainage".

AckwelFoley

unless you live near a stream on the side of a mountain id safely say you wnt have a problem with flash flooding. If you loved on low ground however that would be a different matter

Water gathers at the lowest point and continues to find the lowest point, if its just a "hill" i dont see you ever having a blanket type mass flood down hill.

Having said that, i dont have to live with any outcomes, so better be safe than dorry, but dont spend money on anything thats futile, at least make it somewhat worthwhile... essentially meaning a site survey and professional advise based on that

Kashkai

I'd disagree. Our road slopes (very slightly) right to left and it was submerged under 18 inches of water last August from run offs from fields and from further up the road itself. There are no hills around us so they were not the cause of this flash flooding, just the very heavy rainfall that fell in a 24 hour period that the local ditches (most of which were full of debris and overgrown at the time but have now been cleared out) could not cope with.

We'll have to get used to these heavy rainfall and subsequent flooding events as they become the norm and not the "1 in a 100" year events they used to be.

Tester46

snyper wrote: »

unless you live near a stream on the side of a mountain id safely say you wnt have a problem with flash flooding. If you loved on low ground however that would be a different matter

It certainly would. Bring a waterproof matress;)

40701085

Tester46 wrote: »

It certainly would. Bring a waterproof matress;)

must try that

Cheers for the advice folks, will be getting something organised for sure.