Spit extension and barrier rollover at Blakeney Point and Salthouse: Historic maps and field observations

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In the late 1990s, Brian Funnell used historic maps (1586 and 1797) and aerial photos (1952-1989) of the Blakeney area to calculate the mean extension rate of Blakeney Spit. He also charted landward rates of barrier movement (rollover) in the Salthouse area using a 1649 map. The mean centennial rate of extension of Blakeney Spit was ~3.5 m a-1 implying a likely age of the spit of 3000-4000 years. Change in barrier beach position between 1649 and the present day recorded a mean landward rollover rate of ~0.85 m a-1. These rates concur with earlier estimates and are supported by offshore data published since 2000. This hitherto unpublished work is augmented by more recent field observations from storm surges in 2007 and 2013 that record the episodic nature of barrier rollover and breaching. The most important observations are that shingle-entraining washover events at Salthouse are probably in part conditioned by local topography, favouring topographic lows. In 2013, shingle washover was accompanied by two breach channels. These temporary breach channels were cut principally by seaward drainage of floodwater trapped in the back barrier area following storm overtopping of the barrier. Moreover, the channels were sited on former creek and channel locations visible in the 1649 map. The inherited hydrological topography of the back barrier area thus continues to influence recent coastal geomorphic change.
Original languageEnglish
Pages (from-to)35-63
JournalBulletin of the Geological Society of Norfolk
Publication statusPublished - 19 Nov 2019

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