Somerset

Flooding in the Somerset Levels: A Summary

Geography/Hydrology

The Somerset Levels and Moors contain the settlements (population) of: Taunton (65,000), Bridgwater (36,000) and Glastonbury (9,000) with Cheddar (6,000), Wells (11,000) and Yeovil (40,000) at its edges. The region’s main rivers (catchment area in km2) are the Parrett (1,381), Brue (471) and Axe (186).

The Levels (coastal) and Moors (inland) are two distinct areas of lowlands making up around 600km2 of the 2038km2 combined catchments’ area. The Levels are, on average, 6m above mean sea level and predominantly marine deposits, their fertility combined with high flood exposure has resulted in the main land use being grazing. The Moors are, on average, 3m above mean sea level and a mixture of alluvial deposits and peat/bog soils and their land use is also mainly grazing. The Uplands above the Parrett are largely arable land with slow draining soils while the Uplands above the Brue and Axe are mostly grazing.

The average rainfall throughout Somerset (and the South West peninsula as a whole) is not exceptional however it receives a disproportionate amount if extreme events: over the past 150 years the South West peninsula has received 13 of the UK’s 19 twenty-four hour rainfalls greater than 200mm. A 24hr rainfall is the amount of rain which falls over a 24hr period. The Severn mean high spring tidal range of 12.8m (+/- 6.4m either side of mean sea level) is exceptional and the second largest in the world. At its highest it can reach up to 20 miles inland.

 

History of flooding and flood management

Before drainage began in 1000AD the Moors and Levels were marshland navigable by boat or a series of causeways; only the surrounding uplands were habitable. When the Catholic Church came to the region (most importantly to Glastonbury) and acquired the majority of the land they became interested in making it workable. While limited attempts at draining the marshes occurred, the majority of this activity was focused on sea defence which sealed the gaps in the Levels to protect the Moors from tidal surges.

By the 15th century the tidal defence was largely complete and national growth (and thus food demand) allowed agriculture to flourish on the Levels. The following Black Death, Wars of the Roses, Dissolution of the Catholic Church, Bristol Channel flood of 1607 and Civil War plunged the land (and nation) into depression.

Industrial revolution and Napoleonic wars placed a premium on marginal land allowing wealth to flow into the Levels due to its rich grazing; Somerset became some of the richest (1.5x the national average per acre) farmland in the country. This capital then flowed into Moorland drainage to expand the properties of rich farmers. Reclamation of some areas in the Brue valley led to the expectation that the entire Moors could be successfully drained. However the Southern Moors on the Parrett proved to be a very different beast.

While drains had been constructed in the Southern Moors the removal of marshland had simply replaced the problem with severe annual flooding. Throughout the late 19th century a range of unsuccessful works were attempted and flooding only worsened. This was compounded by the Corn Laws repeal which drained much of the region’s wealth. Responding to fears of disease (malaria and plague had broken out and there was fear of typhoid and cholera) the Land Drainage Act was eventually passed in 1930.

The First and Second World Wars saw increasing demand for national agriculture and a royal ordnance factory near Bridgwater constructed. Investment and engineering works once again returned to the region and the Brue and Axe catchments were largely freed from severe flooding. Despite extensive works the Southern Moors alone has flooded over 30 times in as many years to date.

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