LETTERS: Raising the dam on Hampstead Ponds makes no sense
Published: 21 November, 2013
THE City of London Corporation dam engineers are assessing the safety of the Hampstead Heath ponds.
They propose, in one case, raising the dam between the boating pond and the men’s bathing pond, by 3.6metres and widening the base, making it like Staines reservoir.
The estimated cost is £16million pounds.
It is as if a large crock of gold has been discovered in Europe to be spent, irrespective of actual need, among chums. Good gardening practice and water management would solve the problem at minimum cost.
Instead of dams we should temporarily lower water levels in the pond – as has been done throughout history from the pharaohs on the Nile to modern reservoirs.
They all use sluice gates to regulate water levels, operated manually or electrically. If the bath is going to overflow you don’t build up the sides of the bath, you simply pull the plug out and make sure the overflow is working.
We are not in Holland which, being below sea level has to raise dykes, but on a heath controlling streams.
The Hampstead ponds are man-made the first in 1554 and the last in 1844.
The storm of October 26 was predicted by satellite imaging four days in advance, with different wind speeds predicted to the hour and position.
With such accurate predictions the pond levels could be lowered with hand- or electrically-operated sluice gates creating the capacity to store a vast extra volume of water.
Temporary lower water levels would not harm the margins of Norfolk reeds and nesting places for ducks and coots.
The complete draining of No2 pond for repairs caused no ill effects.
Also, at minimum cost, a series of shallow dry banks across the feeder streams from the Vale of Health and Kenwood areas could slow up the speed of water entering the ponds.
Two additional 30cm drainpipes between the bird sanctuary pond and the boating pond could be done off a wheelbarrow and with a spade.
The tops of the dams could incorporate granite and concrete spill ways to prevent possible under-cutting and rupture of the clay banks of the down¬stream structure of the dams if there is concern about their stability.
In Cambridge it is important that the colleges are not flooded by the River Cam. In the event of a pending flood, the lock gates below Cambridge are opened, and sluice gates above raised. In extreme cases the Cam can be completely emptied.
No one would expect the Cambridge backs to be built up with massive banks yet that is exactly what we are being asked to accept on the Heath.
NICHOLAS WOOD FRGS,