What on earth is a labyrinth weir I hear you ask? A weir is a barrier across a river or pond designed to alter its flow characteristics. A labyrinth weir uses a trapezoidal-shaped weir wall geometry (plan view) to increase the weir length. So choosing a labyrinth weir makes the structure smaller, which was all important in the design proposals as it means less impact to the Heath.
The one labyrinth weir being built as part of the Ponds project is at Hampstead No. 1. It is currently under construction with the concrete walls of the weir still to be poured. You can make out the shape of the weir in the steel reinforcement bars which are already in position.
In the event of a large flood, water will leave the pond, go through the weir and then down the culverts which are currently being laid. The structure protects the earth dam from erosion and possible collapse. It is worth remembering this concrete structure will remain dry except in a very large storm.
The culvert sections are currently being craned into position.
Once this structure is complete it will be buried in topsoil and planted with shrubs and bushes so it fits in with its surroundings.