Costly culvert

[Tarw Coch]

It probably is. The first picture shows the normal summer flow, the second one is where it's blocked up by a combination of twigs and my neighbour's balewrap, but also shows where any excess can run around the top of the culvert so therefore doesn't cause any issues upstream, and the third is what it looks like in the depths of winter. @holwellcourtfarm is absolutely right when he points out that using twin or multiple pipes is actually bad practice as it encourages blockages but I put these pictures up to show how much extra capacity is required.

I wasn’t having a pop at your culvert, I was referring to the one that started this topic

 

[Ffermer Bach]

Exactly this. Folk never allow enough for flood flow.

Multiple pipes are bad news too as debris builds up on the centre and greatly reduces flow just when you need it.

The worst possible option is extending a twin culvert upstream by adding a larger single one. You end up with a debris blockage inside where the twin starts with no safe way to clear it.

If you must cross a watercourse the preferred option is a proper bridge at bank top level. It doesn't interfere with flow at all then.

and when we have Beavers everywhere, and they are protected, there won't be culverts for them to hear the water trickling through and block up (as they think it is a leak in a dam), on the small farm here, I have 12 ditches piped! I never figured Beavers into the equation, hopefully they won't arrive here.

 

[Exfarmer]

Whoever has the longest experience of the site. It's usually developers or new occupant householders who block drains or put silly little pipes in ditches.

"But it never floods like this and I've been here 2 years"

I have a house which sits on the bank beside a brook. At times brook takes a very substantial amount of water. This flows into a culvert which must be 1.5 m diameter and there is a very large grating to prevent detritus flowing in to the drain.
Last year i think AWA or possibly the EA decided to remove the weed growth along the banks , which was quite substantial including some fair size saplings. So what did they do with the resulting material, they left it on the banks for nature to reclaim it. This of course wash washed into the grating , blocking it last winter
Luckily the neighbours noticed in time and at substantial risk to them selves raked this rubbish out of the grating. The water then would be 8 feet deep and threatening to flood a fair few houses.
They are about to build several hundred houses downstream of this point on land which floods every year nearly