Shaping landscapes and industry: linking historic watermill locations to bedrock river knickpoints.

Watermills have been an essential source of mechanical power for over two millennia. Their careful siting often took into account local hydrology, topography, and economic demand, attesting to the important place they held in premodern and early modern societies. This paper highlights the significance of Paul Bishop's work on mills over the last 20 years, which revealed that numerous historical watermills along Scottish rivers were closely located near overly steep stretches of river to maximize waterpower and minimize cost. Termed 'knickpoints', many of these steep erosional features formed thousands of years ago during and after melting of the British–Irish Ice Sheet. Post-glacial isostatic rebound caused rivers to erode into bedrock at rates set by river catchment size and sediment availability. Although bedrock knickpoints along the Scottish coast are relatively stable over human timescales (<10³ years), knickpoints generated by milling in England have been invoked as potential hazards due to their potential to migrate over similar timescales. Bishop's observations on the colocation of knickpoints and watermills encouraged a more comprehensive investigation of the relationship between natural and human systems over the last 250 years and invited re-evaluation of prevailing narratives for the history of water technology and patterns of water-powered industrialization in Britain. [ABSTRACT FROM AUTHOR]