permeable or non permeable driveway?

[Adsibob]

Thinking about the design of our driveway which is on a 10 degree slope from the road to our house (with the house at the bottom of the slope). 

 

I am considering whether it would be helpful, in addition to the drains we are installing at the top and bottom of the driveway, for the driveway itself to have some permeability to it as otherwise when the road floods (which has only happened once since we bought the house a few years ago, but with climate change may become more common) all the water from the road will cross the pavement and slide down the driveway and onto the drain just in front of my house, which won't be very deep and might be overwhelmed by the excess water.

 

My thinking is, even if we go for a permeable solution, the water will just seep into the soil below the driveway and make it's way to the foundations at the front of the house anyway. Whereas if we didn't go for the permeable solution, the water would slide down the driveway and towards the front wall of the house (but not onto the front door as that is on a slightly raised platform), just before hitting the front wall it would mostly get caught by our drainage system there (either a french drain, if we can make that work - see towards the end of this thread - or a linear drain), but if it's a flood it might overwhelm that drain, splash the wall and then seep into the ground anyway. Walls are white rendered. 

 

So is the only non-environmental advantage of the permeable solution in my circumstances that my white walls are less likely to get dirty in a flood? Or am I missing something here. I know that there is an environmental benefit in not displacing naturally falling water by sending it to the sewer, but I'm not sure what good that water would be doing stuck under my driveway/pooling near the foundations if I didn't send it to the sewer.

 

[nod]

We have a similar slope 

whilst planners insisted on permeable 

BC said there was no need for a drain at the bottom He was wrong 

Permeable or not we would flood without it 

 

Edited July 16, 2021 by nod

[Adsibob]

15 minutes ago, nod said:

We have a similar slope 

whilst planners insisted on permeable 

BC said there was no need for a drain at the bottom He was wrong 

Permeable or not we would flood without it 

 

Thanks @nod, good to know. Is that a simple linear channel drain? 

[Temp]

We put in quite a lot of linear drainage around our place. Works pretty well if you have somewhere to send the water.

 

How does the road flood without your house flooding if there is a 10 degree slope down to your house? If you put a linear drain across your driveway entrance will you end up effectively providing drainage for the road? Have you got somewhere other than soakaways to send that much water? whats at the back of your house? Could you run a drain right around the house and off down the slope or would that just flood neighbours?

 

We had the reverse situation. Water going down our drive out onto the road. Put a linear drain across the end and put the outlet into a piped ditch under the road. Effectively we added a long thin gulley to the existing road drainage system.

Edited July 16, 2021 by Temp

[nod]

19 minutes ago, Adsibob said:

Thanks @nod, good to know. Is that a simple linear channel drain? 

Your welcome 

 

I don’t hold to much store in permeable pavers 

I heavy rain it comes down the slope in waves 

[Adsibob]

2 hours ago, Temp said:

How does the road flood without your house flooding if there is a 10 degree slope down to your house?

The house did flood earlier this week, which had never happened before but has now got me thinking. It was such a fun day I posted about it here.

When we bought the house the usual flood risk assessment done as part of the pre-contractual enquiries was low, so really never thought it would ever be an issue... until earlier this week when London got more rainfall in 90 minutes than it typically gets in the whole of July. Watching the news about Germany and Belgium today has got me wondering that maybe these "extreme" weather events will be more common in the future.

We are probably going to put one of these in at the edge of our driveway just before the crossover. So that would be our first line of defence if it rained so much that the water mounted the pavement/crossover. Then we will also have a french drain or linear drain along the perimeter of the house. The question is just whether there is any advantage in making the driveway itself permeable? At the moment, I'm not sure there is such an advantage to justify the extra cost involved.

[Dave Jones]

permeable wont help you in a flood event, nod is correct on our block drive it runs down it in torrents when it comes down hard. Once it stops whats left drains through. Linear drains do need a lot of maintance especially downhill ones as they fill up with crap quickly. Have a silt catcher between them and the soakaway/sewer so its easy to get them unblocked.

[Adsibob]

47 minutes ago, Dave Jones said:

permeable wont help you in a flood event, nod is correct on our block drive it runs down it in torrents when it comes down hard. Once it stops whats left drains through. Linear drains do need a lot of maintance especially downhill ones as they fill up with crap quickly. Have a silt catcher between them and the soakaway/sewer so its easy to get them unblocked.

Thanks, but what's a silt catcher? I get that it catches silt, but how?

[Dave Jones]

you can make one out of a small 250mm inspection chamber, the linear drains  dump into it (the outlet is higher than the bottom so the silt can collect). then every couple months take the lid off and clean it out.

 

ready built larger one to give you an idea.

 

https://www.plasticdrainage.co.uk/600mm-catchpit-silt-trap-for-en1401-upvc-drainage-pipe.html