How it works

As floodwater reaches the outer edge of the barrier, it runs down into the trench housing the folded barrier and its float. The flat top forms a lid on the trench housing the barrier when at rest. As the water level rises in the housing trench, it starts to lift up the float, which in turn starts lifting the concertina-like barrier.

The whole barrier has a waterproof membrane on the outer surface to stop water coming through - the folded barrier is to give it strength against the water pressure. As the flood height increases, the float continues to rise, extending the barrier to whatever height is required. When the floodwaters start to recede, the float and barrier gradually return to their original position in its housing trench.