The Hogsmill in June 2020

A brief interlude of typical English weather this month – grey and wet – though this did little to refresh the Hogsmill greenspace, which after the dry spell is already looking more like late summer than June. But when the sun has shone, our iconic residents have been prominent as they seek food for their broods; and

one effect of a “truncated” summer is that some butterflies, such as marbled white and ringlets, have appeared early this year and in very large numbers in some places, such as Court Farm.

This newsletter reports on volunteer activities to monitor and restore the habitat along the , working with the South East Rivers Trust and local groups, and alongside the Environment Agency (EA) and local water companies, mainly (TW). Although monitoring has resumed, restoration work is still on hold so this month there is another look back at how the Hogsmill corridor has changed over time.

The Hogsmill in June

Rainfall has been about average for June and with the winter rains still boosting the springs, the water level and flow in the main Hogsmill have remained above normal, though as much of the rain was in sharp bursts, including a torrential thunderstorm in , both have fluctuated sharply. But groundwater in the chalk aquifer has fallen markedly after a very dry spring and this is now being reflected in falling water levels in the upstream stretches; and water levels in some tributaries, notably the Tolworth , are well down.

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Maximum Daily River Level Maximum Daily River Level 0.7 1.8 0.6 1.6 0.5 0.4

1.4 0.3

Metres Metres 0.2 1.2 0.1 1.0 0.0 1/1/20 1/2/20 1/3/20 1/4/20 1/5/20 1/6/20 1/1/20 1/2/20 1/3/20 1/4/20 1/5/20 1/6/20

Worcester Park Ewell Bourne Hall

Green Lanes Stream confluence (photo thanks to Pamela) Tolworth Brook

The main beneficiary from the rain has been Himalayan balsam, which with limited “bashing” has shot up all along the banks and is already widely in flower, though it is providing a good resting place for damselflies!

But the rain didn’t come soon enough to rescue some of our “special” meadows: last June they were full of flowers and insects, but now they are parched with wilting flowers providing little succour to wildlife.

June 22nd 2019 Long Meadow June 22nd 2020 2

There has been a “surge” in outfall pollution this month. The Storm Tanks at Ewell, and possibly also at Epsom, overflowed after the thunderstorm. This was short-lived and screens contained most rag, but the strong smell some way downstream suggests a significant sewage spill. There was also a large spill from the outfall by the A3, though probably not sewage, and with TW rapidly locating the source, it did not last long.

Ewell Storm Tanks (photo thanks to Pamela) Malden Way “concrete box”

There has also been a spate of pollution at some “well-known” outfalls. These were short-lasting, in some cases perhaps a misconnection on washing day, and were spotted by chance. They illustrate a change in the nature of pollution along the Hogsmill with fewer outfalls persistently polluted and more isolated incidents.

Knollmead Sheephouse Way Malden Way South Green Lane

If you see pollution along the river or indications of possible pollution, such as dying fish, please call the

Environment Agency Hotline: 0800 80 70 60, and ideally take a photo.

Hogsmill RMI in June

The River Monitoring Initiative (RMI) is a national scheme that uses counts of “water quality sensitive” invertebrates to assess river health. We were again able to survey 6 of our usual 7 sites this month, between 17th and 20th June, with mixed results:

• All 3 upstream sites had good scores of “7-8”, above the long-term average and with high olive and gammarus counts, again probably reflecting the benefits of the high recent flow of water from the springs. The Ewell Storm Tanks were surveyed just before the overflow. The Green Lanes ones were

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sampled soon after the large “surge” and possible Epsom overflow, but while the counts downstream were perhaps down on what might have been expected, the difference was not marked; • By contrast, scores were lower than May at the 3 downstream sites. At the score was still good by historical standards and there was the highest gammarus count since 2014; • But the fall to a “5” at Bonesgate, with large drops in olive and gammarus numbers, was well out of line with the recent stretch of stable results, though it is not known why. The fall to a “3” at the Tolworth Brook may reflect the low water levels there, though as the fall was mainly the result of the absence of caddis that usually have very low counts, it could partly be just sampling variation;

Hogsmill RMI Scores June 2020 10.0

8.0

6.0

4.0 RMI RMI Score 2.0

0.0

GL Upstm GL Downstm Storm Tanks Bonesgate Tol Brook Berrylands

Olives Mayfly Caseless caddis Cased caddis Gammarus

• Marked differences in olive and gammarus “experiences” this month, with both big rises and large falls in numbers compared to May in both species across the different sites; • More variety in the types of cased caddis found, but still no sign of the usual spring/early summer surge in numbers; and • This month’s “unusual catches” were different types of damselfly and dragonfly nymphs found at Green Lanes.

Cased caddis at Green Lanes (photos thanks to Pamela) Dragonfly nymph 4

Crossing the Hogsmill: Then and Now

Despite its short length and narrow width, crossing the Hogsmill has always been a challenge. Up until Victorian times there were only 3 widely-spaced bridges of any size, plus a variety of other “rickety or rustic” ways of going over, or through, the water. Nowadays there are some 40 bridges, though still few suitable for heavy traffic and, with a couple of exceptions, ugly and utilitarian.

The main exception is Clattern Bridge in Kingston, built in the 12th Century and said to be named after the “clattering of hooves” passing over. It has been widened and lengthened, but still appears magnificent. Until the St James Road bridge was built in the 19th Century, it was the only large bridge over the Hogsmill in Kingston; the other major crossing today at College Roundabout was a “watersplash” until the 1920s.

Clattern Bridge 2020 Penryyn Road/Brook Street c. 1900 The other exception is the Blue Bridge on Springfield Road in Kingston, built in the 1890s to link the growing residential areas on either side of the river, reputedly made with a wide carriageway to limit gentry users’ exposure to the sight and smell of a polluted Hogsmill! Sadly it is now rather hidden and lightly used.

1928 Blue Bridge Kingston 2020

The old “industrial” stretch of the river in Kingston at and upstream of Middle Mill had a number of structures and bridges across the river associated with the mills and factories, but the predecessor to today’s Villiers Road bridge – then Oil Mill Lane – does not look as if it would have stood any heavy traffic!

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1900 Oil Mill Lane/Villiers Road 2020

Further upstream there doesn’t appear to have been a major vehicle bridge for almost 4 miles until the Kingston by-pass was built in the 1920s. There was a footbridge and ford at what is now the Green Lane Bridge in New Malden; and another footbridge close to the current one at Sheephouse Way in .

c. 1900 Green Lane New Malden 2020

Of the 3 railway bridges over the Hogsmill, the most impressive, in size if not elegance, is the Malden Manor “viaduct”, completed in 1939. Over the past 50 years it has seen a change in the colour of trains and, like much of the river, a large expansion in bankside vegetation; and now it has a magnificent mosaic.

1970 Malden Manor viaduct 2020 (photo thanks to Paul)

Further upstream 3 brick bridges were built in the 19th Century to provide access from Old Malden Lane to large properties to the north of the river, all of which survive today. The next major crossing was at Ewell Road in Tolworth, where over 100 years ago there was a large bridge over what was an important thoroughfare, albeit not anywhere near as wide as today’s dual carriageway bridge built in 1939.

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c. 1900 Ewell Road Tolworth 2020

At Ruxley Lane there was another “watersplash”. As well as providing a crossing point, this seems to have been a regular bathing spot in the late Victorian era. But it looks to have been a challenge for early motor vehicles, though still a much more attractive rural sight than the present “brick and concrete” bridge.

c. 1910 Ruxley Lane 2020

Further upstream, there were small brick bridges over the river associated with the gunpowder mills, including the pack horse bridge at Ewell Court. The last major crossing was at Road, by the Horse Pond in Ewell. Even today this retains much of its Victorian appearance, though the “strange-looking” horse that once frequented the Pond hasn’t been seen for some time.

c. 1900 Horse Pond 2020

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