Tag Archives: UK

Just How Unlucky Was Britain to Suffer Desmond, Eva, and Frank in a Single December?

Usually, it’s natural disasters occurring elsewhere in the world that make headlines in Britain, not the other way around. But you’d have to have been hiding under a rock to have missed the devastation wrought by flooding in the U.K. last month, thanks to the triple-whammy of storms Desmond, Eva, and Frank. Initial analysis from the Association of British Insurers suggests that the damage done could run to the region of £1.3bn.

But just how unlucky was the U.K.to suffer not just one, or two, but three big storms in one December, and for these three storms to interact in such a way as to produce the chaos that followed?

First it’s worth pointing out that floods in the U.K. are—as is usually the case elsewhere—subject to important seasonal variation (see chart below). The winter months bring the highest number of events, and December does in fact come out (slightly) on top, especially for flooding events of the sort seen last month, which tend to follow heavy rainfall leading to soil saturation (November 2015 received about twice the average climatological rainfall for November in the U.K.).

Source: RMS

The reason this matters is that, when soil is sodden following an extended period of heavy rains, further rains can more easily run off the surface, exacerbating the risk of pluvial flooding. The water will then follow natural and artificial drains until it reaches the closest river network, in which it can accumulate, potentially triggering river or “fluvial” flooding. The runaway effect of the masses of water can also cause what is known as ground-water flooding. This cumulative phenomenon means that—as we saw in December—flooding can persist for a significant amount of time, leading to several flood events in close succession.

A flood CAT model that properly captures these sorts of interactions between rainfall events and hydrological systems will allow not just for an assessment of the likelihood of a single severe event, but also a better understanding of the compounding factors that can lead to the sort of flooding seen in the U.K. last month. And based on our latest RMS pan-Europe flood model, the chances of having three rainstorms lead to major inland flooding over a single December are far from negligible.

Source: RMS Europe Flood Model

The chart above shows the probability of one, two, three, and four flood events for the month of December. What it means is that, on average, every second December in the U.K. has at least one flood event, and every third December has only one flood event. Around every eight years there are two flood events, and a cluster of three flood events happens once every quarter-century.

Now, this does not mean that flooding on the scale just witnessed happens on average every 25 years—just that this is the average period for seeing three flood events in one December. Even if it did, it wouldn’t mean that the U.K. can rest on its laurels until 2041… this is just a statistical average. It is quite possible for clusters to hit several years in a row—a so-called “flood-rich period”.

This gets to the real nub of the issue. The question of how often this sort of flooding takes place in the U.K. is almost by-the-by. The point is that it isn’t rare as hen’s teeth, and so the U.K. needs to be prepared. And what was most shocking about December wasn’t the flooding itself, so much as the sheer lack of resilience on display. A media storm has understandably been whipped up regarding the level of investment into flood walls and so on, but protective infrastructure is only part of the equation. What is needed is not just flood walls (which can actually be counterproductive on their own), but a wider culture of resilience. This includes things such as flood warning systems, regular evacuation drills, citizens having personal plans in place (such as being ready to move furniture to upper levels in the case of an alert) and, critically, the ability to respond and recover should the defences fail and the worst happen (which is always a possibility). The U.K. is the world’s sixth richest country—it has the resources to cope with flood events of this magnitude… whether they happen every five, ten or 25 years.

High Tides a Predictor for Storm Surge Risk

On February 21, 2015, locations along the Bristol Channel experienced their highest tides of the first quarter of the 21st century, which were predicted to reach as high as 14.6 m in Avonmouth. When high tides are coupled with stormy weather, the risk of devastating storm surge is at its peak.

Storm surge is an abnormal rise of water above the predicted astronomical tide generated by a storm, and the U.K. is subject to some of the largest tides in the world, which makes its coastlines very prone to storm surge.


A breach at Erith, U.K. after the 1953 North Sea Flood

The sensitivity of storm surge to extreme tides is an important consideration for managing coastal flood risk. While it’s not possible to reliably predict the occurrence or track of windstorms—even a few days before they strike land—it is at least possible to predict years with a higher probability of storm surge well in advance—which can help in risk mitigation operation planning, insurance risk management, and pricing.

Perfect timing is the key to a devastating storm surge. The point at which a storm strikes a coast relative to the time and magnitude of the highest tide will dictate the size of the surge. A strong storm on a neap tide can produce a very large storm surge without producing dangerously high water levels. Conversely, a medium storm on a spring tide may produce a smaller storm surge, but the highest water level can lead to extensive flooding. The configuration of the coastal geometry, topography, bathymetry, and sea defenses can all have a significant impact on the damage caused and the extent of any coastal flooding.

This weekend’s high tides in the U.K. remind us of the prevailing conditions of the catastrophic 1607 Flood, which also occurred in winter. The tides reached an estimated 14.3 m in Avonmouth which, combined with stormy conditions at the time, produced a storm surge that caused the largest loss of life in the U.K. from a sudden onset natural catastrophe. Records estimate between 500 and 2,000 people drowned in villages and isolated farms on low-lying coastlines around the Bristol Channel and Severn Estuary. The return period of such an event is probably over 500 years and potentially longer.

The catastrophic 1953 Flood is another example of a U.K. storm surge event. These floods caused unprecedented property damage along the North Sea coast in the U.K. and claimed more than 2,000 lives along northern European coastlines. This flood occurred close to a Spring tide, but not on an exceptional tide. Water level return periods along the east coast are varied, peaking at just over 200 years in Essex and just less than 100 years in the Thames. So, while the 1953 event is rightfully a benchmark event for the insurance industry, it was not as “extreme” as the 1607 Flood, which coincided with an exceptionally high astronomical tide.

Thankfully, there were no strong storms that struck the west coast of the U.K. this weekend. So, while the high tides may have caused some coastal flooding, they were not catastrophic.

Managing the Changing Landscape of Terrorism Risk

RMS has released an updated version of its Probabilistic Terrorism Model, which reflects the considerable changes in terrorism risk for Canada, Denmark, Ireland, Italy, and the U.K. as well as the decreased frequency of large-scale-terrorism events for each of the five countries.

To inform the new view of risk, our scientists carried out a comprehensive analysis of global attack and plot data from the past decade. We focused heavily on large-scale attacks – those with the potential to threaten the solvency of an insurer.

The analysis showed that incidents of large-scale attacks have steadily and significantly decreased, which corresponds with a rise in the funding and sophistication of major intelligence agencies in the west.

Our approach to terrorism modeling follows three principles, which have been validated by data on intercepted plots, past successful attacks, and recent intelligence leaks:

  • Effective terrorists seek to achieve optimal results relative to their effort
  • Their actions are highly rational
  • They are highly constrained by pervasive counter-terrorism measures

Of the estimated 200,000 documents taken or leaked by Edward Snowden, one of the most relevant validations of the RMS model is an N.S.A. presentation that explains the routing of international telecommunications traffic. A very significant proportion of international telecommunications traffic is routed through the U.S. and Europe which, coupled with advances in big data analytics and plummeting data storage costs, has made intelligence collection easier and more robust than it has ever been.

 an N.S.A. PRISM presentation explains the routing of international telecommunications traffic

According to available data on the frequency of plots and attacks, the risk of a large-scale attack has been in decline since 2007, but the risk of smaller-scale attacks perpetrated by lone-wolf operatives and homegrown militants remains high.

However, we have learned over the past decade that terrorism risk levels are fluid and can change quickly. With the rise of the Islamic State in Iraq and reports of its successful recruitment of foreigners, as well as ongoing instability in Afghanistan and Pakistan, the risk outlook can change at any moment.

The RMS Probabilistic Terrorism Model incorporates multiple risk outlooks to provide users with the agility to quickly respond to any changes in terrorism risk. RMS is committed to updating its terrorism model as frequently as necessary to provide the most up-to-date, granular, and accurate view of global terrorism risk.