Unlike flooding from rivers, surface water flooding can happen many miles from a river, often in places that people wouldn’t expect because it’s a long way from a river or stream – it happens simply because there is nowhere else for the rainwater to go. Risk ratings are measured as:
High Risk - an area which has a chance of flooding of greater than 1 in 30 (3.3%) in any one year.
Medium Risk - an area which has a chance of flooding of greater than 1 in 100 (1.0%) in any one year.
Low Risk - an area which has a chance of flooding of greater than 1 in 1000 (0.1%) in any one year.
Very Low Risk - an area in which the risk is below 1 in 1000 (0.1%) in any one year.