Susceptibility of wetland types to degradation by stormwater input

Susceptibility of wetland types to degradation by stormwater input

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Susceptible		Non-Susceptible
Highly Susceptible Wetland Types ¹	Moderately Susceptible Wetland Types ²	Slightly Susceptible Wetland Types ³	Least Susceptible Wetland Types ⁴
Sedge Meadows Open Bogs Coniferous Bogs Calcareous Fens Low Prairies Coniferous Swamps Lowland Hardwood Swamps Seasonally Flooded Basins	Shrub-carrs^a Alder Thickets^b Fresh (Wet) Meadowsc,^e Shallow Marshesd,^e Deep Marshesd,^e	Floodplain Forests^a Fresh (Wet) Meadows^b Shallow Marshes^c Deep Marshes^c	Gravel Pits Cultivated Hydric Soils Dredged Material / Fill Material Disposal Sites

1. Special consideration must be given to avoid altering these wetland types. Inundation must be avoided. Water chemistry changes due to alteration by stormwater impacts can also cause adverse impacts. Note: All scientific and natural areas and pristine wetlands should be considered in this category regardless of wetland type.
2a, 2b, 2c. Can tolerate inundation from 6 inches to 12 inches for short periods of time. May be completely dry in drought or late summer conditions.
2d. Can tolerate +12” inundation, but adversely impacted by sediment and/or nutrient loading and pro- longed high water levels.
2e. Some exceptions.
3a. Can tolerate annual inundation of 1 to 6 feet or more, possibly more than once/year.
3b. Fresh meadows which are dominated by reed-canary grass.
3c. Shallow marshes dominated by reed-canary grass, cattail, giant reed or purple loosestrife.
4. These wetlands are usually so degraded that input of urban stormwater may not have adverse impacts.

Notes: There will always be exceptions to the general categories listed above. Use best professional judgment. Pristine wetlands are those that show little disturbance from human activity.