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The Weather - Printable Version

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The Weather - drpeterwardle - 24th July 2007

I am pleased to report to BAJR that I have not so far been affected by the weather (unusual rainfall) and neither have my projects but....

On the news Tewkesbury Abbey has been flooded for the first time since 1760. Burford church has also been flooded.

While the damage to said beautiful buildings is unfortunate how far could archaeology/history contribute to the greater debate on cilmate change, and policy on building on flood plains, by mapping when buildings have been previously flooded and thus establish how unusual the weather event actually is.

The current weather has more or less not been recorded before and the flooding is exceeding the 1947 (worst in the last 100 years) which was a winter event.

So has the weather event never actually occurred before or in fact is it say a natural 200 or 1000 year event?

How as a discipline can we help?

Discuss.

Dr Peter Wardle
Goring on Thames







The Weather - kevin wooldridge - 24th July 2007

I'm not sure that archaeology can help much (other than to suggest this has happened before, this will happen again), but maybe we could be part of the general education campaign that informs the wet and muddy public of the effects of climate, rain, sea and rivers on our natural and built environment.

We could maybe start with the reasons why the Chilterns, Cotswolds, Yorkshire Wolds and North Downs are so defined, having a lot to do with the natural floodplains of various river systems......

Kevin

PS Waiting to see today's photographs of the Thames Barrier closed for the first operational time in its history....


The Weather - Gog - 24th July 2007

Presumably stone churches will survive floods better than modern houses?


The Weather - voice of reason - 24th July 2007

The Thames Barrier is closed several times a year on abnormally high tides and has been since its creation. What is unusual is that this time they are creating a dam to hold back the water from the sea to give the volume of river water space to move into.


The Weather - Paul Belford - 24th July 2007

Some of our projects have been affected in the West Midlands.

These recent floods are exceptional because they are in summer, but I should think something of this order occurred once every 100 to 200 years throughout history. Just look at the 'Water Gate' at Worcester. I am told by the engineers in our local authority that this is a '1-in-100 year event'.

Nevertheless it is striking from what I have seen that the worst-affected areas are mainly 19th, 20th and 21st century suburbs. The historic medieval (and earlier) core of most of our affected towns and cities are relatively unscathed. The fact is that for Tewksbury Abbey this is a 1-in-250 year event.

Areas such as (for example) the Lower Don Valley in Sheffield, or parts of the Severn floodplain, or even those low-lying suburbs of north Oxford have all been built on during the last 200 years. Even the most cursory glance at historic mapping shows all of these areas to be relatively undeveloped until relatively recently. Increasing canalisation and regulation of rivers and watercourses gave people confidence to build in historically flood-prone areas, and 99 years out of 100 they are fine.

Only in the last couple of hundred years has the pressure for space been such that formerly 'out-of-bounds' areas have been used for housing. Earlier industrial uses (such as mills and forges) were obviously affected by such events but needed water power so there was a trade-off. In the space of most commonly held 21-year leases on such sites the chances of a major flood were sufficiently low to be worth the risk. The decline of water power and the pressure for cheap housing has meant that many flood-prone areas have subsequently been built on.

Therefore in my view the current problems are more to do with over-population and hubris than exceptional weather patterns.

To answer the question: archaeology can provide the long view which puts these events into perspective.



The Weather - vulpes - 24th July 2007

Quote:quoteTongueresumably stone churches will survive floods better than modern houses?

Dunno, depends. According to the EH advice note on Flooding and Historic Buildings: 'It is rare for the structural integrity of a historic building to be compromised'. However this does not rule it out. Once flood levels exceed around a metre above floor level structural damage is more likely.

The intensity of the flooding is also significant as damage could be caused by the scouring action of fast flowwing waters potentially undermining foundations - often much shallower in older buildings.
However, in the majority of cases damage will be limited to floor and wall coverings, fixtures, fittings etc. and if treated properly may have no significant long term effects whether the building is old or newish.

Longer term problems can be caused in historic buildings by efflorescence of salts held in masonry or brickwork. If impermeable (and inappropriate) modern paints or renders have been applied this can cause 'spalling' where the masonry surface cracks and peels. Lime based plaster as used in older buildings can also survive flooding without replacement as can structural timber. So you may have a point.


The Weather - Digger - 24th July 2007

I think the (prolonged) exposure to raw sewage is an issue for any structure. Dont forget about the various medieval bridges (Evesham and Pershore way for example) that have had the odd boat/caravan/car slamming against them.

By the way Peter, the Govenment didn't take it's own recommendation on this occuring, so don't think they'll take to much notice of the archaeologists.:face-huh:


The Weather - Weegie - 24th July 2007

In support of Vulpes' point, I have worked on saturated historic buildings, and the drying-out process can indeed cause spalling and other loss of historic wall surfaces. This can be mitigated by applying a sacrifial coat of limewash, so that the evaporation takes place on that surface rather than on the historic masonry. From memory, the sacrificial coat has to be renewed when it flakes until the building is dry, so it's a fairly labour-intensive process.

Repeated flooding can certainly cause damage to masonry - as at Hailes Abbey, where we did some work last year in support of a flood prevention scheme.

Brian


The Weather - vulpes - 24th July 2007

Exposure to raw sewage (albeit much diluted) is likely to be a significant risk for people, not structurally for the buildings any more than exposure to the water itself is.

Damage from things hitting buildings and structures is governed by the intensity of the flooding, bridges are by their nature mid stream so particularly prone.


The Weather - m300572 - 24th July 2007

One answer to the problem is to change the way we manage the landscape - block upland blanket bog drainage, plant tree belts along rivers, create washlands that will flood short term to slow the pulses of flood waters down the rivers and insits that all new builds have rainwater catch systems for flushing toilets etc so that water is caught and used rather than adding to the load in the sewerage system and water butts - if every house in the catchments of the floods caught fifty gallons of water then released it after the main flood pulse had passed it would have some effect even if it didn't prevent flooding of every property.