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The Flooded Somerset Levels

Image by brizzle born and bred
Does This Look Familiar?

The Somerset Levels under water! in 1929

Let’s dip into the weather archives.

West Country Weather 1929 – Was this Global Warming?

David Cameron describes the Somerset floods as “biblical”. He should delve into the weather archives 1929/30, or other years, were much wetter?

February was cold enough to allow skating at Uley and Badminton Park.

The Stroud canal was frozen and a steam tug was employed to break the ice on the Gloucester to Sharpness canal. The minimum temperature fell to —13.9°C (7°F) during the month in Bristol and it was only very slightly warmer in Bath.

By March however the weather was completely different and in Bath the highest temperature for a March day on record was observed at 22.2°C (71.9°F).

On the 3rd of August Bristol had some very heavy rain resulting in approximately 3 inches of rain in twenty four hours. On the same day the Bath Chronicle reported that it was a “long-time since Bath was visited by such a heavy rainstorm.”

In 20) minutes 1/3rd of an inch of rain had fallen and then a “violent wind got up.”Bath recorded 1.79 inches (45 mm) falling in one 24 hour period in October during two days of particularly wet and rough weather.

In Bristol it was reported that 2.05 inches (52 mm) fell on the 6th of October.

In November Bristol had its second wettest month on record with an exceptional 9.9 inches (252 mm). Following on from this record month was another high rainfall totalling 8.1 inches (205 mm) in December. All this extra rain actually followed a very dry period, especially in Bath, when for the first seven months of the year the city only recorded 6.8 inches (173 mm) when _the average is 16.2 inches (411 mm), or only 42% of the average.

Research and consultant hydrologist, Dr Colin Clark quantifies a possible solution to the current flooding on the Somerset Levels.

information source www.waterpowermagazine.com

When King Alfred hid in the Somerset marshes from the Danes in 878, he could scarcely have imagined that the marshes of Athelney and the lands of Wessex to the North East would be drained and occupied during both winter and summer, since beforehand, these lands could only be used during the summer: thus the name of my home county – the land of the summer pastures. The Saete of Somersaete, comes from the summer pastures of Norway which are called Saeters or Seters.

In showing our respect for the freedom of others from serious floods, I would like to describe some of the ignorance and neglect that has led to the recent flooding of the Somerset levels, and to then shine a beam of hope for the future, which quantifies a solution to the problem.

No one disputes that the past three months have been very wet. But how does it compare with the past?

There was serious flooding in 1854, 1872-3 and 1929-30. During the latter flood at Taunton, from November 1929 to January 1930 537mm were recorded, which is over 70% of the annual average. The floods lasted from December to February. For the same time period in 2013-14 the rainfall in the upper Brue, which drains into the Levels, was 434mm.

An analysis of the highest consecutive three monthly rainfall since 1766 shows that this is the fifth highest, giving it a return period of about 1 in 50 years. This result excludes 1960, when Bedlamgreen in the upper Brue recorded 556mm. Before 1766 possibly the worst flood in historical times was that of 1607: I will mention this event at the end of this paper, since it was not caused by prolonged rainfall.

It would therefore not be correct to state that the present floods are in anyway linked to changes in air temperature, both local, or global.

Several Acts of Parliament in the early 19th century led to improvements in the drainage of the Levels. In the uplands, field boundaries often consisted of a hedge and ditch. Both were maintained, often on an annual basis. Where they did not lead directly or not at all into a watercourse, ditches retained a considerable volume of water.

During the late 1970′s I calculated the likely volume of potential storage of field ditches in the upper Brue catchment. The Brue is one of three main rivers that drains into the Levels.

It shows the extent of field ditches, excluding those by highways. Assuming a cross section area of 0.7 m2 gives a storage volume of about 77000m3. Many ditches have a bigger cross section. This is big enough to have cancelled out nearly all of the overflow volume during the flood at Bruton in May 1979, when 36 houses were flooded.

Applying the same density of ditches over the upland catchments of the Tone, Parrett, and Brue and assuming a cross section area of 5m2 gives a storage volume of about 16Mm3. I will describe the way in which this could improve the situation in the penultimate section of this paper.

From the 17th century pumps were used to remove excess water from the land. The earliest pumps were driven by windmills, but steam power, followed by diesel and electricity enabled much greater volumes of water to be carried away. In the scholarly account of the draining of the Somerset levels by Dr Michael Williams, published in 1970, Williams never gave a single figure for the capacity of the pumping stations.

Very rarely a flood may occur that is not caused by heavy and prolonged rain, but a tidal surge and storm surge as well. It may also have been caused by a tsunami. This probably took place in January 1607 which led to flood waters up to 4m deep.

A contemporary report by W. Barley and I.Bayly tells us: "that the cuntrey all along to Bridge-water was greatly distressed thereby, and much hurt there done it is a most pitifull sight to beholde what numbers of fat Oxen, were there Drowned: what flocks of sheepe.

It has been estimated that 500-2000 people were drowned during this flood. It affected much of Somerset and also South Wales. It is hoped that such a catastrophic event does not find the land and its people on the Levels as ill prepared as they were in 2013-14.

(to read this article in full click on link www.waterpowermagazine.com/features/featurefloods-on-the-…)

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