Flood Expert Says We Ignore Historical Data At Our Peril

By Paul Homewood 

 

h/t Tony N

 

http://www.bbc.co.uk/news/uk-wales-35685686

 

Just once in a while, you hear someone talk with a bit of commonsense about climate issues. Step forward, Professor Mark Macklin.

(Roger Harrabin and his thought police must have missed this one!)

 

 

Lives and homes are in danger because the flood risk in Wales is being underestimated, according to a rivers expert.

Aberystwyth University’s Prof Mark Macklin said magnitudes could be 40% greater than planned for in some areas.

He told BBC Wales Natural Resources Wales (NRW) is failing to use all historical data to predict the risks.

A NRW spokesman said its flood maps were not underestimating the problem but it was considering using the data.

Prof Macklin, who heads the university’s river dynamics and hydrology research group, questioned why NRW uses river gauges from the past 50 years only to predict flood risk.

He told Week In Week Out his researchers had found "evidence of much larger and more frequent floods" in the 18th century, which were between 20% and 30% larger.

Among areas most at risk, Prof Macklin said parts of the upper River Severn in Powys could see flood magnitudes between 20% and 40% greater than what had been experienced since 1980.

"We will need to rethink and re-map our flood plains to look at changing flood risks. If we don’t, we’re going to put more properties and livelihoods at risk," he said.

 

Despite £7m being spent on new flood defences in Llanrwst in Conwy Valley, residents on Conway Terrace had their properties flooded on Boxing Day 2015 when a temporary dam was not put up in time.

An NRW spokesman said while it did not accept its flood maps were underestimating the risks, it was aware of Prof Macklin’s work and was considering a pilot study to see if it could use the data in its modelling.

http://www.bbc.co.uk/news/uk-wales-35685686

 

Macklin’s comment about using data from the last 50 years is significant, because Professor Stuart Lane, of Durham University, came to very similar conclusions in 2008:

 

Prepare for more floods – in ways we are not used to – that’s the message from experts at Durham University.

Last summer was the second wettest on record and experts who have studied rainfall and river flow patterns over 250 years say we must prepare for worse to come.

Professor Stuart Lane, from Durham University’s new Institute of Hazard and Risk, says that after about 30 to 40 less eventful years, we seem to be entering a ‘flood-rich’ period. More flooding is likely over a number of decades.
Prof. Lane, who publishes his research in the current edition of the academic journal Geography, set out to examine the wet summer of 2007 in the light of climate change. His work shows that some of the links made between the summer 2007 floods and climate change were wrong. Our current predictions of climate change for summer should result in weather patterns that were the exact opposite of what actually happened in 2007.

The British summer is a product of the UK’s weather conveyor belt and the progress of the Circumpolar Vortex or ‘jet stream’. This determines whether we have high or low pressure systems over the UK. Usually the jet stream weakens and moves northwards during spring and into summer. This move signals the change from our winter-spring cyclonic weather to more stable weather during the summer. High pressure systems extend from the south allowing warm air to give us our British summer.

In 2007, the jet stream stayed well south of its normal position for June and July, causing low pressure systems to track over the UK, becoming slow moving as they did so. This has happened in summer before, but not to the same degree. Prof. Lane shows that the British summer can often be very wet – about ten per cent of summers are wetter than a normal winter. What we don’t know is whether climate change will make this happen more in the future.

However, in looking at longer rainfall and river flow records, Prof. Lane shows that we have forgotten just how normal flooding in the UK is. He looked at seasonal rainfall and river flow patterns dating back to 1753 which suggest fluctuations between very wet and very dry periods, each lasting for a few years at a time, but also very long periods of a few decades that can be particularly wet or particularly dry.

In terms of river flooding, the period since the early 1960s and until the late 1990s appears to be relatively flood free, especially when compared with some periods in the late 19th century and early 20th Century. As a result of analysing rainfall and river flow patterns, Prof. Lane believes that the UK is entering a flood rich period that we haven’t seen for a number of decades.
He said: “We entered a generally flood-poor period in the 1960s, earlier in some parts of the country, later in others. This does not mean there was no flooding, just that there was much less than before the 1960s and what we are seeing now. This has lowered our own awareness of flood risk in the UK. This has made it easier to go on building on floodplains. It has also helped us to believe that we can manage flooding without too much cost, simply because there was not that much flooding to manage.”

He added: “We have also not been good at recognising just how flood-prone we can be. More than three-quarters of our flood records start in the flood-poor period that begins in the 1960s. This matters because we set our flood protection in terms of return periods – the average number of years between floods of a given size. We have probably under-estimated the frequency of flooding, which is now happening, as it did before the 1960s, much more often that we are used to.

“The problem is that many of our decisions over what development to allow and what defences to build rely upon a good estimate of these return periods. The government estimates that 2.1 million properties and 5 million people are at risk of flooding. In his review of the summer floods Sir Michael Pitt was wise to say that flooding should be given the same priority as terrorism.”

Professor Lane concluded: “We are now having to learn to live with levels of flooding that are beyond most people’s living memory, something that most of us have forgotten how to do.”
Flooding is one of the issues covered by the Institute of Hazard and Risk Research at Durham University where Prof. Lane is a resident expert. The IHRR, which launches this week, is a new and unique interdisciplinary research institute committed to delivering fundamental research on hazards and risks and to harness this knowledge to inform global policy. It aims to improve human responses to both age-old hazards such as volcanoes, earthquakes, landslides and floods as well as the new and uncertain risks of climate change, surveillance, terror and emerging technologies.

https://www.dur.ac.uk/news/newsitem/?itemno=6468

 

   

The blame for building on flood plains is a long and complex one. But it is time that planners, politicians and developers now accept the mistakes made in the past, and learn from them. Simply blaming climate change is a cowardly option.