For decades there was concern that after periods of heavy rain the capacity of Llanmaes Brook was insufficient to carry the increased flow of water.
As a consequence floods sometimes occurred in Llanmaes, Boverton and Ham Manor So the precursor of the Environment Agency, the River Authority, oversaw the creation of a lagoon in this area to safeguard new residential areas nearby.
The Environment Agency has now enlarged the lagoon's capacity, so the flow of water downstream can be regulated in wet periods.