Recommended design frequencies (storm – for use with simple design methods, flooding – for use with complex design methods), according to the recent standard (EN 752, 2008).
| Location . | Design storm frequencya . | Design flood frequencya . | ||
|---|---|---|---|---|
| Return period (1 in N years) . | Exceedance probability in 1 year (%) . | Return period (1 in N years) . | Exceedance probability in 1 year (%) . | |
| Rural areas | 1 in 1 | 100 | 1 in 10 | 10 |
| Residential areas | 1 in 2 | 50 | 1 in 20 | 5 |
| City centers/industrial/commercial areas | 1 in 5 | 20 | 1 in 30 | 3 |
| Underground/railway underpasses | 1 in 10 | 10 | 1 in 50 | 2 |
| Location . | Design storm frequencya . | Design flood frequencya . | ||
|---|---|---|---|---|
| Return period (1 in N years) . | Exceedance probability in 1 year (%) . | Return period (1 in N years) . | Exceedance probability in 1 year (%) . | |
| Rural areas | 1 in 1 | 100 | 1 in 10 | 10 |
| Residential areas | 1 in 2 | 50 | 1 in 20 | 5 |
| City centers/industrial/commercial areas | 1 in 5 | 20 | 1 in 30 | 3 |
| Underground/railway underpasses | 1 in 10 | 10 | 1 in 50 | 2 |
aFor those design storms or design floods, no surcharge shall occur.