ON Friday, March 28, members of Thorverton History Society were treated to a talk entitled “The Exe Through Time” by Dr Jenny Bennett.

We had a high turnout of our members to listen to the detailed research and field work compiled by Dr Bennett for her geology masters on the subject of the Exe and its changing course over time, through the many influences of geology, man and climate.

This was a fascinating insight into our local area and obviously a passion of the researcher, who was able to illustrate her talk throughout with evidence from her personal field work and photos as well as historical cartography, traditional archaeological resources, historical sources and newer techniques, including LIDAR, Light Detection and Ranging, a remote sensing method for capturing and creating 3D models of the real world.

The geology upon which the river is based is Quaternary, sourced from the radial drainage patterns from Exe Head on Exmoor, southwards 96 kilometres to the English Channel at Exmouth.

Beyond the limits of glaciation in the British Isles, the river pattern and valley width is dictated primarily by the geology.

The river flows through a steeply incised valley in the north, gradually widening towards the south, primarily influenced by the underlying geology, having a narrower river valley running over harder Carboniferous sandstones and shales, whilst expanding and cutting a wider valley floor over softer Permian and Devonian “red” sandstones, breccias and mudstones on its route to the sea.

Her combined data revealed that in many places the river seems to have had a long history of channel switching and then reoccupying channels, while man made leats, particularly around Exeter (its lowest bridging point from the Roman period) and its medieval mills, have substantially altered the river course over time.

One of the most obvious traces of this are the remnants of the old Exe Bridge now essentially a traffic island!

The river remains tidal below Exeter, due to a pronounced bedrock step, and accounts for the usage of the river and then the canal (which may have followed a paleo channel itself) to the sea after weirs were built to control river traffic.

This evidence shows through in many of the historical maps and drawings as well as in meteorological records of active climate change, such as increased rainfall and chronicled extreme events.

Understanding the behaviour of the river from these sources, clues from place names such as Marsh Barton, historic parish boundaries and Jenny’s own fieldwork establishing the traces of previous channels and courses remaining in the landscape (around Brampford Speke and Up Exe for example) will only assist future response to flooding and river management.

The subject clearly engaged our audience and many additional local examples were volunteered as well as the possible contributions of re-introduced wildlife, as in the beavers on the River Otter, were discussed and the evening gave us many opportunities to engage and interpret our local landscape in a more thoughtful and informed way.

Our thanks go to Jenny for her excellent talk.

Ann Marshall