T4 map components are dominated by alkaligrasses (usually Nutka, occasionally Hultén's, alkaligrass).  T4 components are found just above arrowgrass (Triglochin spp.) and goosetongue (Plantago maritima) (T3) in estuaries. 

T4 loosely corresponds with Vince and Snow's (1984) 'Outer Mudflats Zone 2', estimated to be inundated on higher spring tides, or an average of 15 times per summer on the Susitna Flats (with a range of 10-20 times per summer), in upper Cook Inlet, Alaska.  Vince and Snow found that water was retained for 2-5 days per inundation. 

Nutka alkaligrass is the most common dominant, although Hultén's alkaligrass is sometimes encountered, alone or mixed with Nutka alkaligrass.  This is the most extensive tidal unit in the project area because of the large areas dominated by Nutka alkaligrass at the mouth of the Kenai River.

Organic Clunie series soils are common, however Vince and Snow (1984) found soils with a relatively low organic content on the Susitna River flats in Upper Cook Inlet Alaska.