Alleviation of flooding from Road Drains and Sewer.

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Alleviation of flooding from Road Drains and Sewer.

Post by emjay » Sun Oct 02, 2016 7:59 pm

In June we had 87 mm rain in 70 minutes ! The water ran from main road down our cul-de-sac on the surface and in the rainwater drains (and the sewer) and came up at the end of the road. We have the lowest bungalow. The water ran into our front garden, along, south, to one end, across the side garden and out under our fence onto a mowed field that is 20 inches lower than our side garden. It came to 1 inch below our front door sill. Surface water also flowed round the other end of the bungalow where it washed away the sewage back-flow that was being forced out of the inspection chamber at that end of the building and this combined flow ended up meeting up with the major flow at the southern side garden and departing under the fence.

The fence needs replacing as the bank down to the field has become loose and the fence poles cannot be re-fixed as the ground is too soft everywhere. We plan to concrete tall fence poles into a trench in the ground that will go 30 inches below the level of the field. We HAD planned to retain our garden end with concrete gravel boards slotted into the fence posts, but no longer want to risk retaining enough water to flood the house. We are currently considering a 20 inch no-fines concrete wall cast above the solid concrete securing the fence posts and running land drain pipes from the front and the back of the bungalow into this to diffuse any future flood into the field.

Are we within our rights to do this ? The rainfall was described as a 1 in 100 year event. The water authority are dragging their heels about fitting a back flow prevented in the sewer. The district council may get back to us sometime. We are keen to have some resolution before the winter storms and rains recur.

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Re: Alleviation of flooding from Road Drains and Sewer.

Post by ColinG » Mon Sep 18, 2017 5:25 pm

Someone is bound to accuse me of hijacking this head. I apologise, for I am but the subjects are so close it seems the sensible thing to do. If the mods do not like it I will willingly start a new thread.

We live in a new(ish) build - 5 years old. We are not on main drainage so our run off and sewage treatment plant water runs into a drainage ditch, the ditch copes fine with that. However a road drain (that collects surface run-off from the road) empties into our ditch. Usually this is ok but when we have these downpours (they are more and more frequent) the ditch floods our sewage treatment plant (completely submerges the outflow) with the risk being raw sewage being thrown out into the environment. This happens after just a few hours downpour so the risk of the ditch actually overflowing is very real if constant rain is experienced. Have asked the Council to check if we drain to the road drain or if the road drain drains to us - we are still waiting.

Also asked if it was proper for the Council to use a private ditch to drain the road without permission. The frightening answer was yes and the responsibility to maintain the flow rests with the land owner not the council. Thus any blockage, no matter if it is our ditch or a connecting ditc, is our problem if our land floods. If this is so then maybe I should have the right to stop the flooding by blocking off the drain!

Is something being missed?

Hugh Jaleak
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Re: Alleviation of flooding from Road Drains and Sewer.

Post by Hugh Jaleak » Thu Nov 09, 2017 2:54 pm

Firstly, apologies for being late to the party, but I dont bother so much with this site these days. Fed up of having to log in every time, and Site Admin seem unwilling or unable to correct the various faults with the site, that have been raised by other regular contributors for some time previous to my hiatus.

'emjay', the problem you describe seems to be with the sewers 'surcharging' through the sheer volume of water. There is no quick fix to this sometimes, provided the sewers are clear, and capable of running at 100% capacity, such a volume of rain in a short period may well swamp the system, and unfortunately, as seen so much more in recent times, flooding does occur. The Authorities simply haven't got the finances to attend to every incident of this nature sadly, although with the 'SUDS' (Sustainable urban drainage systems), program, it is being taken seriously.

In the short term, providing a channel for the excess water to drain from your garden onto the lower ground shouldn't be an issue, the water is going to find its way there anyway, all you are doing is speeding up its progress and mitigating any risk to your home. I know of a previous scenario whereby the excess water flowed to the bottom of a cul de sac, the bungalow in the bottom corner had resigned themselves to their fate, and opened the garage door front and back to allow the flow through in times of heavy rain. The problem was alleviated in 1989 by the construction of a network of new sewers around the estate, and the laying of a 900mm diameter storm sewer through the neighbours garden!

ColinG, I think you need to look at 'Riperian ownership' for the ditch through your property. Often such watercourses can be regarded as a public sewer for surface water runoff, but still remain the responsibility of the landowner(s) to maintain. Look at fitting a non return valve to the outfall from your treatment plant.

I would also be pretty sure you have absolutely NO right to block off the outfall from the Highway drainage, doing so and finding another property floods as a direct or indirect result could land you in a lot of trouble. The responsibility to ensure the continued passage of the water past your land lies with the subsequent landowners to maintain their ditches, and/or the responsible authority if the watercourse subsequently becomes culverted.

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Re: Alleviation of flooding from Road Drains and Sewer.

Post by jonahinoz » Wed Oct 10, 2018 8:38 am


If this is a man-made watercourse, then surely those responsible for diverting water into it are responsible for for bhow it affects other properties?

<<< There is no quick fix to this sometimes, provided the sewers are clear, and capable of running at 100% capacity, such a volume of rain in a short period may well swamp the system, >>> Surely the drain-makers have to design in a Factor of Safety.? Being capable of running at 100% capacity is not sufficient? I suggest that a Factor of Safety of "2" should be the minimum. EG: The drains should be capable of running a 200% of maximum expected/calculated capacity. If it's a round drain, doubling the capacity does not mean doubling the diameter.

As for the not being able to afford to upgrade the capacity of the drains ... just imagine their reaction if you told them you cannot afford to pay your water rates.

Are the Water Authorities still privatised. and paying dividends to their shareholders?


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