Celebrating 25 Years of the Chilterns Chalk Streams Project

SCARP SLOPE STREAMS
‘Water in a Dry Landscape’ is designed by CCSP to look in detail at the ecological status and opportunities
for restoration of chalk scarp streams between the M40 and the A41 which feed into the Thame catchment.
The project is a partnership between River Thame Conservation Trust (RTCT) and CCSP, delivered in three
phases as part of the Chiltern Conservation Board’s ‘Chalk Cherries and Chairs, Landscape Partnership
Scheme’, supported by the National Lottery Heritage Fund. Phase One, led by CCSP, started with a
volunteer-led survey of 47 sites across the project area to assess water quality at the source, middle and
end reaches of scarp streams to identify key water quality changes along their length.
Barton Springs
Site surveys were also carried out to identify opportunities for enhancement and restoration along the
different streams. Through this work, a series of maps was created to show water quality variations, and the
team agreed that the remainder of the project would focus on the Horsenden Brook, parts of which are
designated as a chalk stream.
Initial surveys of the Horsenden Brook indicated that the stream had lost its population of brown trout; eDNA
sampling by the RTCT confirmed that there is no remaining or relict trout population in the stream. On the
positive side, the surveys indicated that there are opportunities to remove impoundments along the stream,
which should lead to the natural re-stocking of the trout population. Over time, the river channel has been
straightened, and the gradient is now so steep that there is little by way of refugia for fish in strong flows.
As a consequence, when there is a flood, any small fish will get washed out of the catchment and down
through weirs that will form barriers to their upstream migration.
The next phase of the project is to work with a group of landowners and a farmer cluster in the Princes
Risborough area to identify and prioritise river restoration options along the brook, with a view to delivering
restoration that will improve connectivity and habitat, with the long term aim to reintroduce brown trout. It is
hoped this will form a basis for more projects in partnership with RTCT looking at the chalk streams interface
between the Chilterns escarpment and River Thame tributary catchments.
50 | CELEBRATING 25 YEARS OF THE CHILTERNS CHALK STREAMS PROJECT