Posted by: waterworks | April 10, 2008

27. Armadas, monks and meanders

Following on from Thread 26, it seems possible that those meandering river channels so archetypically associated with lowland England may owe something to the Spanish Armada.  Until the Middle Ages, braided channels were far more common in western Europe than they are today (‘braided’ denotes the presence of a cluster of gravely islands  aits or eyots in ye olde English – around which channel waters diverge and convolute).  According to recent research by Robert Francis, braiding gave meandering a run for its money when deciduous woodland still covered lowland Britain.  Severed limbs of timber – parted from trees by such tortures as wind, mildew or rot – were in more plentiful supply for streams and rivers than today.  The Medieval river channel would therefore have been no stranger to the kind of large woody debris that might form a nucleus for sediment deposition and island bio-construction (corroborating his thesis, Francis can quote laboratory studies where the addition of bank-side vegetation has led to a complete change in channel flow pattern from braided to meandering). 

During the later Middle Ages, oak forest was  widely uprooted to provide timber for Tudor warships, thereby drastically altering river channel form and process.  In Landscape and Memory (1996), Simon Schama argued that from Tudor times onwards the patrician role of the British monarchy as ‘guardian of the greenwood’ played second fiddle to a militaristic foreign policy.  Material demand for felled timber and farm land also grew in line with the rapidly expanding population, while dissolution of the monasteries freed forested land to entrepreneurial bidding – inevitably accelerating rates of deforestation.  With trees left thin on the ground as a result of maritime ambition and monastic decline, the potential for river braiding most likely diminished somewhat – and well-defined meanders became a relatively more common river landform in some lowland environments.    

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