Appendix III - Hydrologic Modifiers
land surface is exposed by tides less often then daily; the area from mean low
tide to extreme low spring tide. Equivalent to Cowardin's Irregularly Exposed.
tidal water alternately floods and exposes the land surface daily, from mean low
(lower low on West Coast) to mean high (higher high on West Coast). Equivalent
to Cowardin's Regularly Flooded.
tidal water floods land surface less often than daily. The area must be flooded
by tides at least once yearly as a result of extreme high spring tide plus wind
plus flow. The area extends from mean high water inland to the maximum extent of
tide plus the splash zone. Equivalent to Cowardin's Irregularly Flooded except
in tidal Riverine, Lacustrine, and Palustrine areas where if an area is only
irregularly flooded by fresh tidal waters, the appropriate non-tidal modifier,
e.g., Temporarily Flooded, Seasonally Flooded, Semipermanently Flooded, will
substrate is usually exposed, but surface water can be present for variable
periods without detectable seasonal periodicity. Inundation is not seasonally
predictable and is dependent upon highly localized rain storms. This modifier
was developed for use in the arid West for water regimes of Playa lakes,
intermittent streams, and dry washes but can be used elsewhere when appropriate.
This modifier can be applied to both wetland and non-wetland situations.
Equivalent to Cowardin's Intermittently Flooded modifier.
surface water is seldom present, but substrate is saturated to surface for
extended periods during the growing season. Equivalent to Cowardin's Saturated
surface water is present for extended periods during the growing season, but
is absent by the end of the growing season in most years. The water table after
flooding ceases is very variable, extending from saturated to a water table well
below the ground surface. Includes Cowardin's Seasonal, Seasonal-Saturated, and
Seasonal-Well Drained modifiers.
surface water persists throughout growing season in most years except during
periods of drought. Land surface is normally saturated when water level drops
below soil surface. Includes Cowardin's Intermittently Exposed and
Semipermanently Flooded modifiers.
surface water present for brief periods during growing season, but water
table usually lies well below soil surface. Often characterizes flood-plain
wetlands. Equivalent to Cowardin's Temporary modifier.