Flooding?

Flotsam

Active member
So we've had some wet weather and there's some floods but who really believes that this rain although exceptional is unprecedented?

I remember when I was caving in the 1970's the controversy over grant aided upland drainage, I understand that it's still going on,
 

menacer

Active member
The words "In my lifetime" seem to be trotted out with with regularity.
It seems a dumbing down or denial of civil servants in the planning department over the  "said lifetime", translated to -  its ok to build houses on flood plains because we have never seen it flood. - The results don't seem that unpredictable to me. Flood plains themselves are evidence of such unprecedented events.(before concreting over more of the land)

 

bograt

Active member
Err-- 'flood plain'? maybe there's a clue in the phrase???

New local housing development retained the traditional name of the plot ---'Miry Meadow!' ---, I suspect the second and third floor flats are the more popular.
 

paul

Moderator
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ChrisJC

Well-known member
To me, the problem is that these kind of events have probably happened hundreds of times in 'geological time', but people tend to think that 'living memory' is somehow a useful yardstick.

Chris.
 

Rhys

Moderator
It seems to be that long established towns and settlements are flooding though. Not just new developments.
 

cap n chris

Well-known member
ChrisJC said:
To me, the problem is that these kind of events have probably happened hundreds of times in 'geological time', but people tend to think that 'living memory' is somehow a useful yardstick.

Agree!
 

andrew

Member
Rhys said:
It seems to be that long established towns and settlements are flooding though. Not just new developments.

That can happen when you build nearby or change farming methods etc, also adding flood protection to one place often moves it somewhere else. It is a complex sytem.
 

Rhys

Moderator
andrew said:
Rhys said:
It seems to be that long established towns and settlements are flooding though. Not just new developments.

That can happen when you build nearby or change farming methods etc, also adding flood protection to one place often moves it somewhere else. It is a complex sytem.

Agreed.
 

Simon Wilson

New member
River Nidd between Harrogate and York. It went above the previous highest recording and the gauge has been there for 83 years.

Nidd%2027_zpsplzdjunk.jpg


 

Andy Farrant

Active member
When bridges and 200 year old buildings get washed away and Malham Cove sports a waterfall, then these floods are clearly unprecedented in the sense that similar magnitude events have not happend since many of the towns in the region grew up during the industrial revolution. I doubt very much if flood events prior to the industrial revolution were as high simply because urban development tends to exacerbate flood peaks. And to get two events such as this (including setting a new UK 24 hour rainfall record) in the space of just a few weeks in the same region is highly unlikely. And this follows on from several other record breaking rainfall events in the recent past.

People and especially the media use 'living memory' as a yardstick simply because they don't neccessarily have the historical records to hand. Larger events may have happened on geological timescales, but those were probably under different climatic conditions (eg glacial meltwater floods) and occured prior to urban development so it is a bit of a fallacious argument. Predicting flood magnitudes and extents is a complex business, and not simply a case of looking at an area of flat land by a river. Roads, bridges, embankments, culvets and natural barriers can all influence flood levels. That said, the media does have a very short memory; the Boscastle floods for example, whilst unusual, were not unprecedented  - the Lynmouth floods of 1952 were far worse.

What is clear is that to prevent such floods in future requires a more holistic whole catchment approach, including reforesting uplands, creating more natural meandering river channels, installing sustainable urban drainage and using more approproate farming methods to reduce runoff.  Hats off to the rescue teams, local councils and the EA who are having to deal with this event during their Xmas holidays and under difficult circumstances.
 

Simon Wilson

New member
ChrisJC said:
To me, the problem is that these kind of events have probably happened hundreds of times in 'geological time', but people tend to think that 'living memory' is somehow a useful yardstick.

Chris.

'Geological time' events might have little relevance. We are now into the 'anthropocene'. This morning the Environment Agency's deputy chief executive David Rooke told the BBC that we need to look at the historic records that were used to predict what flood defenses we need to provide and to reassess if that is still valid in the face of a changing climate. He said, "We are moving from a period of known extremes to one of unknown extremes."
 

pwhole

Well-known member
Having got through the Sheffield flood in 2007, which was pretty savage (for Sheffield), it was clear that poor infrastructure and river management were as much to blame as high rainfall. As the city has five significant rivers, with the largest two merging in the city centre, and literally hundreds of streams (and some old colliery soughs) feeding into those, it's always been a water-managed city, not least as the hydro-power systems put in place up to and beyond the industrial revolution demanded control and careful management of the natural supply.

Much of the upstream and downstream sections of the Don, as well as in the centre, have very high walls in place, partly as flood-defence, and partly as control structures to feed water in and out of long-gone mills, dating from the 17th Century up until now. These should have maintained the river integrity even in extreme floods, but the problems were mostly exacerbated by the sheer amount of dead trees, scrap and rubbish washed down from the banks, which then rapidly accumulated under Lady's Bridge and dammed the river, causing it to overflow down the Wicker in minutes. It was like a mini-version of the Japanese tsunamis last year, with the added junk causing more damage, and at least one death.

As most of the river bank upstream is woodland, followed nearer to the city by Victorian factories and other industrial units, it was inevitable that the junk which had accumulated over time would end up in the river. Similarly, many of the streams run underground in culverts, many of which had not been maintained or cleared out for decades. If the banks had been tidy, old trees removed and the walls repaired or renewed, it's arguable that some of the flooding wouldn't have happened, or at least not as catastrophically. But the water levels were huge, with massive saturation underground, and the normally protective sandstone 'aquifer' underlying the city just couldn't hold any more.

Ironically, myself and many other rope-access workers were able to work on huge sections of the flood-defence walls last year, consolidating (or literally rebuilding) the walls, removing problem vegetation, and even working within the culverts, repointing and rebuilding. I pretty much got paid to go 'urban caving' at that stage, which was rather satisfying. But the city, working with the EA and other bodies, is making a huge effort to ensure this never happens again. Luckily, with Sheffield being so hilly, most housing development is above flood levels, but the Don Valley industrial area is the lowest, and so is just as critical from an economic standpoint, even if the risk to personal property/safety is less. However, Catcliffe, near the M1, is very low indeed, and at much higher risk of this sort of event. They are on the flood plain of the Rother, and have flood gates nearby on the river, but as in York, in 2007 the water level was just too much, the gates were raised and the flood plain flooded, as it's meant to. I've often wondered why that settlement exists where it does, as again, it's not all new, but it's obviously a flood plain.
 

Madness

New member
There's a stream that runs behind my mum's house and through the corner of her garden. Just outside her garden is what we used to call 'the pond hole' when we were kids. It was basically a depression that flooded during excessive rain, thus 'storing' flood water. Both the 'pond hole' and the stream used to get regularly dug out by the farmer. This digging out stopped many years ago and so the stream and 'pond hole' are sedimented up. It now floods in much more frequently.

I suspect that this is the case for many old watercourses. They have been neglected and so cannot move or store water as they did in the past.
 

Hunter

Member
Concrete, Tarmac & roof tiles all increase run off when it rains instead of bare earth which absorbs the rain fall and slows run off.
Flood defences keep water 'funnelled' in areas where it once had room to spread.
Pour more water into a funnel than the outlet can take & it overflows.
I'm guessing the brains who design & build flood defences or allow development on the natural flood plain account for the fact that stopping rivers spreading where they do naturally means that the water is held back which must increase the risk of flooding up stream of the defences.
 

royfellows

Well-known member
ChrisJC said:
To me, the problem is that these kind of events have probably happened hundreds of times in 'geological time', but people tend to think that 'living memory' is somehow a useful yardstick.

Chris.

Good comment Chris.
In geological terms, 1,000 years is a 'short time-scale'
 

grahams

Well-known member
royfellows said:
ChrisJC said:
To me, the problem is that these kind of events have probably happened hundreds of times in 'geological time', but people tend to think that 'living memory' is somehow a useful yardstick.

Chris.

Good comment Chris.
In geological terms, 1,000 years is a 'short time-scale'

And apart from that, past records are bound to be exceeded at some point - simple statistics.

Over the past 30 or 40 years the weather has been pretty benign in this country. We have not seen the extremes that occurred in the '50's for example with massive regular flooding and some very harsh winters. Whether we are returning to more extreme conditions remains to be seen. More statistics gained over the next few years are required.
 

pwhole

Well-known member
Flood defences keep water 'funnelled' in areas where it once had room to spread.

Indeed - sadly, however, many British towns and cities have developed along rivers specifically because of the advantages of doing so, but urban development (even ancient) will always increase the risk of damage to property. If there's no people, there's no damage. But where will everyone live if not where they are? It's not like they can just move a whole town up into the hills, especially when surrounded by National Parks.

In the olden days, a stone cottage with a flagstone floor would take a day to slosh out and you were arguably back in business. No fitted carpets and TVs and other perishable items to worry about. Not that I'm advocating a return to the olden days, but a re-assessment of housing design and domestic priorities is probably long overdue. Like if you're building on a flood plain, build them on stilts or something. Just needs a bit of imagination, but that's often sorely lacking in the higher echelons of town planning and government departments.
 

martinr

Active member
pwhole said:
........ a re-assessment of housing design and domestic priorities is probably long overdue. Like if you're building on a flood plain, build them on stilts or something..............

I live on the coast, about 5m above normal high tide. My "house" was built in 1995. All the living accommodation is on the first floor. The ground floor is entirely garage / utility.  Anything I value (other than my classic cars which needless to say are in the garage) is stored upstairs, Beats me why other new houses on flood plains and in coastal areas aren't built the same way. If it ever floods, I'll just lock up the house and drive uphill.
 

RobinGriffiths

Well-known member
Has the winter 'mode' been consistent over the last 3 years or so? A series of depressions in the Atlantic spewing forth storms every week or so?  And this is before they started naming them. They'll have to get a new set of names soon in any case.
 
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