Building on flood plains, effect on others.

27 Jan 2008
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Llanfair Caereinion, Nr Welshpool
United Kingdom
If anyone builds on a flood plain they do one would hope know what they are doing, and take measures to stop or reduce damage due to flooding.

However the problem is not just the building on the flood plain, but building near rivers further down stream, where years ago a storm would be absorbed by flood plains so water had a longer time before it reached the sea, now rain today, flood within hours because no reservoir to hold water back for a time.

OK we do build reservoirs like lake Vyrnwy which could be used to hold back water, but to do that they would need to be kept only half full, so then in summer there could be a water shortage, and the reservoir is owned by a water authority to supply fresh water, not the government as a flood defence.

I am lucky in a way, I live up stream so the Banwy may get high, but not for long, the local railway did cancel one train at 11 am, but by midday it was going down again. But further down looking at days not hours for water to raise and fall. And flooded fields in Welshpool can save Shrewsbury from flooding.

In Flintshire it was actually the county council who caused the flooding by dumping spoil when building Theatre Clwyd on the Alun flood plain to turn it into a park, OK that was some years ago, but they can hardly then complain if some one else does it.

If building is allowed on a flood plain then it should include a reservoir so loss of flood plain does not cause flooding further down stream.

Having Vyrnwy reservoir build by Liverpool controlling the flooding of Shrewsbury means Shrewsbury has very little control of how much water is held back, and it seems Vyrnwy reservoir could release water into the Dee instead of the Seven, but Bangor on Dee also has flooding problems, but then Bala could hold water back, Liverpool has apologised to the Welsh and said how they did not need all the Welsh reservoirs they built, so the water level could it would seem be dropped, but all the flood control needs to be in one authorities hands not spread out so one has to send requests to the other.

As a p.s. the flooding in Mold was made worse by the old now disused railway, which becomes a second river when the Alun gets too high, it always has done, then they build two supermarkets, and a fire station with a massive underground complex underneath it. Why when Rhydymwyn is so close?
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its a real problem.

roads and houses increase rate of run off

I know in theory houses should be able to discharge all the rainwater into soakaways within the curtilage but doesnt work so well in practice.

woodland is great at absorbing rainwater, tree roots prevent soil erosion, tree canopy keeps the soil dry as does root absorption so soil has more capacity. Lawns, driveways, house roofs not so much
I had a friend with 20 acres of woodland, he had what he called beaver dams, made during the dry season with stakes and wood wound to gather they would not stop the water flow, but they would reduce the speed and as a result reduce erosion. Once you get to the rivers it's in the main too late, but dams with pipes allowing water to flow, but the level with raise and fall as the flow alters have a damping effect. The also mean water always flows helping the crops.
I had a friend with 20 acres of woodland,

Why doesn't he just chop them down and burn them?
Its what every one else does.
Who cares what effect it has on others.
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He was passionate about his woodland, he had a website think it was called natural forest practice where he showed all his experiments and explained to anyone who would read it what they should do. Unfortunately he is now in a care home, he has a caretaker in his woodland, but his website has not been updated for a couple of years. There are still photos on his site accredited to me, but don't live near him any longer so not been there for a few years.

Actually he could not chop down his trees even if he wanted, one it is a SSSI site, and two to get trees out of the woodland would cost more than he could get for the tree. There is no logging road, last time trees were removed was to build ships for first world war, so most trees are only just over 100 years old.

This is what he called a beaver dam

Showing the stream in flood, it slowed down the flow.