Water is allowed to pond on the top layers of bioretention areas to maximize the amount of stormwater runoff treated by the system.
The ponding layer helps to slow the flow rate of incoming stormwater, allowing it to permeate into the layers of biofiltration media in a controlled manner.
If systems are not maintained, then water may pond indefinitely – and fail to drain away from the top layers of the system.
Indefinite ponding is often an indicator that these systems need to be assessed by a maintenance team. For example, water outlets may be blocked, or bioretention media may be compacted and lacking permeability. A maintenance inspection can help to assess the source of the issue and prevent further damage to the system.
In larger stormwater treatment systems, ponding zones can provide capacity for the retention of water. These areas slow surface velocities and mitigates flooding – and should be routinely inspected, particularly after large rainfall events or storms.
