What are Tufa Flushes?
The City of Bath is famous for its Limestone-based buildings, giving a rich, honey-coloured feel to the City. But the limestone in the ground is also permeable and dissolves in slightly acidic water. Where this water emerges as springs from the hillside, deposits of the mineral called tufa start to form – the calcium carbonates precipitate from the water and form a soft spongy rock. Over time, a series of dams can be formed, trapping nutrients and creating a base for the proliferation of a very specific habitat, supporting marginal plants, amphibians and invertebrates.
So special is this formation, that Bath & North-East Somerset Council’s ecologists pronounced it as of county-level importance.
In fact, this is the only site within Bath that exhibits this phenomenon. And it comes about because of two special conditions.
Firstly, the site is the natural drainage slope for the hill of Odd Down, a large highly-developed flat-topped hill to the south of the city. Rainwater from this hill, gathered from the hard developed surfaces, naturally drains down the slope through permanent surface streams. One of these feeds the nearby childrens’ park at Moorfields (‘the Sandpits’).
Secondly, the site has lain undisturbed since the second world war, free from cultivation and only occasionally grazed.
This has allowed the springs to develop to their present state.
In fact there are two sets of springs and 5 tufa outcrops, the major tufa area in the West of the site has been joined by a newer area at the eastern end, caused originally by the excessively wet winters around 2013, which led to new semi-permanent surface streams ( some of which found their way into local residents gardens). While these have now (2020) subsided , the formation of a new tufa area appears to be permanent.
For more information on the springs, see our Geology page.
Other local Tufa formations.