| System | Estuarine |
| Subsystem | Estuarine Tidal Riverine Coastal |
| Tidal Zone | Estuarine Tidal Riverine Coastal Intertidal |
| Definition | The substrate in this zone is regularly and periodically exposed and flooded by tides. This zone extends from MLLW to the extent of tidal inundation, i.e., the extreme high water of spring tides. The Coastal Intertidal is exposed regularly to the air by tidal action. |