Design storms and return periods
Service targets depend on asset criticality. Main corridors often require stricter criteria than local streets.
- Use jurisdiction-approved intensity duration frequency data.
- Check climate uplift assumptions for long-life infrastructure.
- Document accepted nuisance flooding depth and duration thresholds.
Hydraulic grade line control
Pipe diameter alone does not guarantee performance; pit losses, backwater effects, and downstream controls set behavior.
- Track HGL profile to identify surcharge and overland flow initiation.
- Audit inlet capture assumptions under high approach velocity.
- Validate outfall tailwater scenarios during concurrent river events.
Resilience sequencing
High-value upgrades combine detention, conveyance, and smart control rather than only replacing pipes with larger diameters.
- Prioritize bottlenecks with largest avoided flood damage per dollar.
- Integrate temporary storage in parks, median basins, and rooftops.
- Use phased works packages that preserve current service during construction.