Green infrastructure slows and infiltrates stormwater near where it falls, instead of letting it run off impervious surfaces straight into storm drains.
Q_runoff = C · i · A
C_green < C_impervious
- Rainfall intensity — how hard it's raining; higher intensity generates more runoff volume.
- Rain garden count — vegetated depressions that capture and infiltrate runoff from nearby roofs/pavement.
- Bioswale width — vegetated channels along streets that slow and filter flow; wider swales absorb more.
- Green roof coverage — fraction of building roofs planted, reducing runoff at the source.
Blue runoff particles that reach a green feature (rain garden, bioswale, green roof) are absorbed (turn green and fade); particles that reach the street without being intercepted count as flooding.