Acceptable frequencies of drainage surcharges damming up to the ground level for calculations checking the operation of the drainage systems according to DWA-A118 (2006).
| Lp. . | Location . | Frequency of overflows (once in N years) . |
|---|---|---|
| 1 | Rural areas | 2 |
| 2 | Residential areas | 3 |
| 3 | City centers/industrial/commercial areas | More than 5 |
| 4 | Underground/railway/road and pedestrian underpasses | More than 10a |
| Lp. . | Location . | Frequency of overflows (once in N years) . |
|---|---|---|
| 1 | Rural areas | 2 |
| 2 | Residential areas | 3 |
| 3 | City centers/industrial/commercial areas | More than 5 |
| 4 | Underground/railway/road and pedestrian underpasses | More than 10a |
aWhen local security measures are not applied, the frequency of overflows is 50.