Stadhampton Mill Bypass

In February 2025, River Thame Conservation Trust (RTCT) registered a rather interesting new Riverfly monitoring site. At first glance, it might look like its location on the map is incorrect, as it doesn’t appear to be on a watercourse…

This is because the site is on a bypass channel that RTCT constructed so recently that it doesn’t appear on our database’s map yet! The channel was created to allow the passage of fish, which was blocked along the main channel, Chalgrove Brook, by a concrete weir. This is part of the Trust’s work towards removing all barriers to fish movement in the Thame catchment. The Stadhampton Mill Fish Pass opened up 3.25 km of chalk stream habitat, to which 12 brown trout were transported and riparian and aquatic plants were introduced.

The RTCT is now using Riverfly surveys as a method to monitor the success of this scheme and see how the new habitat is developing over time — a great example of the wide range of uses Riverfly data can have, beyond just catching pollution events. As can be seen below in the screenshot from riverflydata.org, the first three months of surveys have all seen an RMI score of 10, with a range of taxa identified:

"We’re thrilled with the Riverfly results from the newly created bypass channel at Stadhampton Mill. The appearance of stonefly nymphs—hardly ever found in the River Thame catchment—is an excellent indicator that we’re on the right track with our chalk stream restoration work. It's incredibly rewarding to see such tangible progress. For years, River Thame Conservation Trust has been working on improving the Chalgrove Brook, and thanks to our enthusiastic and growing team of Riverfly monitors, we’re now adding new monitoring sites all along the brook. Soon, we’ll have a robust picture of the brook’s health from source to confluence with the Thame."
— Chels Hothem, Riverfly Hub Coordinator, River Thame Conservation Trust

You can read more about this project on River Thame Conservation Trust’s website:

Stadhampton Mill Fish Pass

Restoration in Action: Fish Surveys Reveal the Success of the Bypass Channel Restoration