Flooding expertise – a product of historic collaboration and community spirit

It will be interesting to see whether the lasting memory of the floods will be of people bewildered by the recurrence of flooding exceeding a 1 in 100 return period three times in a decade, such as in Cumbria, or of communities like Cockermouth pulling together in the face of disaster to support each other.

The scene in Cockermouth, Cumbria in December 2015, only six years after the town was devastated by serious floods. Image: morebyless, via Flickr
The scene in Cockermouth, Cumbria in December 2015, only six years after the town was devastated by serious floods. Image: morebyless, via Flickr
  • Updated: 11 January, 2016
  • Author: Mike Chrimes , Engineering Historian

The need for communities to pool resources to meet the challenge of flooding is one reason historically that the expertise of professionals - who would now be considered civil engineers –was developed centuries before the age of Smeaton.

In areas like the English fenland and the low countries of Holland, local communities were collaborating together in the post-Roman era to build and maintain drainage and flood protection works. Officials with positions like the 'Dike Reeve' ensured moneys were collected from local people, and labour was provided, to clear ditches and raise embankments.

The ongoing need for flood protection meant that expertise was developed and by the 13th century experts in flood protection and hydraulic works such as sluices acted as consulting engineers across Europe.

For practical skills to be effective, scientific understanding of hydrological and hydraulic problems is required. Data has to be accrued and useful interpretation needs valid formulae and informed expertise. In Europe it was not until the 17th century that the hydrological cycle was widely accepted, and at the end of that century Edme Mariotte related rainfall catchment data to flow data on the Seine in Paris. His work was translated into English in 1718 and scientists began to develop instrumentation to measure flow, evaporation and precipitation.

For 18th century engineers like Smeaton and Rennie the collection of rainfall and streamflow data was an imperative. Engineers' interests therefore coincided with 'amateur' meteorologists in establishing data.

Those with a holistic approach realised they needed rainfall and flow data to design a sensible scheme. Rennie developed a drainage scheme for the East, West and Wildmore Fens north of Boston (1800) that involved catchwater drains to collect the upland water on an unprecedented scale for Britain. New drains were dug, with Rennie taking pains to keep the upland and fen waters separate. The works cost private investors over half a million pounds but had paid for themselves within seven years. The works were preceded by extensive surveys into rainfall and flow, and have generally stood the test of time.

Early engineers like Smeaton probably used their knowledge of the work of Italian and French engineering scientists to calculate flow. However two of the best known formulae were developed by engineers working on the drainage of bogs in Ireland in the 19th century- the Manning formula (1889), and the rational method developed by Thomas Jame Mulvany (1851). The latter has been used by generations of engineers designing for floodwaters.

It is worth remembering some of what he wrote more than 150 years ago:

"It is evident that there may be such a state of the atmosphere that no appreciable amount of evaporation may occur during the continuance of a flood, and no matter what may be the water storing properties of the geological formation of the district they may have been completely exhausted by previous rains; and therefore, the maximum discharge will mainly depend upon the quantity of rain, and the extent and comparative elevation of the catchment to the discharge channel."

This is of course the reality behind the latest floods. The flood level in Carlisle a few weeks back was at least 1m higher than any previous event since records began in 1771.

Before engineers began to compile hydrological data as an essential tool, knowledge of historic floods often relied on marks on buildings which can still be found in many locations as a reminder of what a 100 or a 1000 year flood may bring.

14th century hotel in Cochem, Germany, showing water level marks from historic flood events
14th century hotel in Cochem, Germany, showing water level marks from historic flood events
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