March 2022

Late in the month the lakeside prominade between the watersports area and stadium was re-opened to the public. This revealed the finished work for dam safety there. It remains a mystery why it is not possible to re-instate the lost seats along this length. Mature trees are retained there, and seats fixed into the surface of the new path would not constitute a material obstacle to the 1-in-100 year flood which has to be able to pass safely there. The sheet piling has been nicely capped with wood, and this hides the eroded tops of the old piles. One wonders how long the piles will remain intact and the wood will remain nice and neat and whether there is provision for renewal or replacement when the time comes? The steepened access up to the prominade has made boat access less easy and the same for disabled access. Preparation for works downstream from the new outfall has begun, and the broad outline of the new channel in the public park is indicated by gaps in the existing fencing. By the end of the month, the trench to take the pipe under the path to take the new course of the brook back to join the old course was dug. An oyster shell was found at the bottom of the trench, 90 cm deep in the London clay, suggesting that it is a geological, rather than archaeological find.

I made a careful search of the lake margins, seeking the exposed "silt" predicted by LB Merton should the lake be lowered to Brown's design. There was almost none. Just a small area beside the stadium, where a bed of Yellow flag iris and Sweet flag was just slightly above the lake level and a somewhat larger area beside the island in the far western arm of the lake. This is despite the level of the lake being appreciably lower than in Brown's design. I wonder how much longer Merton can continue their claims in the face of evidence to the contrary. The reason, of course, is that Brown designed his lake to withstand fluctuations in level by steepening its banks.

Unfortunately, the trees that were felled in Ashen Grove Wood have been disposed of in Horse Close Wood, apparently without consulting the managment plan for the wood, the Friends of Wimbledon Park, nor local experts. This has led to some unfortunate changes, the worst of which is a big log heap right on top of the patch of Dog's Mercury. The map is from the 2015 managment plan for the wood, where I have circled the mercury in red. The Mercury was in full flower a month ago, but I could see no sign of the Mercury now. Some may remain squashed below.

The other main difficulty is that some of the logs have been used to define the edges of the footpath leading into the Glade at the other end of the wood, but not to a sensible desgin. This is a pedestrian path and we had an existing proposal to reverse the destruction wrought by the National Grid when they took out their heavy kit there. New planting would have narrowed the path to a metre or two width and replaced the lost woodland either side. The photo shows the excessive width here.

The emergency drawdown pipe at the new weir was closed around the 20th to allow the flow down the tributaries to refill the lake. There has been little rain recently and the lake level on the 28th had risen by just 4 cm above the level four weeks earlier and a further 1 cm by the 30th. The rate of filling will depend upon rainfall and so is unpredictible. 

The field season for botanical survey is on us, so I have resumed my visits to log the plants that arrive beneath the veteran oak and in the various places where we have planted new trees and shrubs. This shows that we still don't have meadow management of the long grass across the perimeter path from the tennis courts. This is necessary to prevent the long grass being overtaken by Bramble, Blackthorn and Ivy.

The opening of the prominade enabled me to complete the monthly standard walk bird count on the 30th. Both Canada goose and Greylag numbers were a little lower than expected. Unusually, four immature Mute swans, last year's cygnets, remain at the lake. Normally they would have been sent off by their parents by now. Coot numbers remain on the long-term average, again suggesting that the surge in numbers from the recovery of waterweed is over: bad news for lake water quality. There was a pair Gadwall ducks. This species has been seen more often in recent years but, so far, without confirmation of breeding. Tufted duck numbers have been decreasing in recent years, so it would be premature to attribute the low count of 10 birds to any more than this recent trend. It was nice to hear loud Nuthatch song in Ashen Grove Wood, despite the damage wrought by the dam safety works. It seems that enough old trees have survived to provide the natural holes that it uses for nesting. Blackbirds were in full song. Peak song occurs when the female is incubating. In contrast, there was no Song thrush song as this species sings much less when the female is brooding. Why these closely-related species differ so is not known. The Wren is known to suffer from bad winter weather and has been in decline locally in the last 20 years, so it was good to hear 11 birds in song, close to the long-term average. A pair of Stock doves seem to have claimed a hole in the veteran oak for their nest site this year.

Hawthorns were in full leaf and only a few early flowers were evident. In contrast, Blackthorn flowering was waning and the leaf buds just bursting. One or two Oaks were leafing up but most had just sweling buds. Ash trees were flowering. Elders were in full leaf. Elm suckers were leafing up. Brambles and Ivy were sending out new shoots. I saw just two early native Bluebells in Horse Close Wood. Let's hope those trampled by heavy use over the last two years will recover. The deep blue flowers of Green alkanet were to be seen beside the woods and hedges.