The council's Surface Water Management Plan (2019 updated version) identifies and prioritises the areas of Portsmouth at greatest risk from surface water flooding, defined as heavy rainfall creating more water than the drainage system can cope with. Most flooding in Portsmouth is caused by surface water which, by its very nature, is very difficult to predict. This makes providing accurate and timely warnings difficult.
Drains in the gutters at the side of the road, known as gullies, can overflow in times of heavy rainfall. Gullies may not appear to be coping with heavy rainfall, but do allow some time for water to subside and then, if the drainage does not improve, let the City Helpdesk know on 023 9283 4092.