Wetland Creation/Expansion
Potential permits required: CWA 404, Threatened & Endangered Species, NHPA, Floodplain
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Wetlands are sensitive ecosystems that provide numerous benefits to the surrounding areas. They can be created (or expanded) on your land to:
• Increase wildlife habitat for aquatic and semi-aquatic animals (such as waterfowl, amphibians and fish)
• Provide storage for flood waters
• Stabilize streambanks
Typically, wetlands in the Lefthand, Big Thompson, Little Thompson and Saint Vrain areas are found on terraces along the stream or in depressions within the floodplain (including abandoned stream channels or oxbows). They can range from cattail marshes, to wet meadows, to sandbar willow shrub lands, to alder shrub lands. Often, wetlands can form quickly (i.e. after just one growing season) if there is sufficient water.
Successful wetland creation requires an in-depth understanding of groundwater, soils, and vegetation. A wetland expert should be consulted to determine if a wetland can be successfully created on your property and what methods are needed to effectively establish wetlands.
Also, streams are active systems. Any wetland creation or expansion should be carefully designed to avoid being “blown out” during the next flood. Consulting with a water resources engineer will evaluate the links between the proposed wetland and the stream system.
Creating wetlands require three inter-connected conditions:
1. Hydrology (water)
This is the most critical condition. Without enough water to saturate or flood the soils for a sufficient period of time, wetlands won’t develop. Typically, wetlands are created or expanded by grading down to the existing water table or the stream elevation. Determining where to grade to depends on:
• Adjacent existing wetlands (either a streambank terrace floodplain depressions/oxbows) – A wetland expert will determine the exact depth, but it should generally match the existing wetlands elevation.
• Creating a wetland in an upland – Hydrology may be much more difficult to determine in existing uplands, because you would need to know where the groundwater elevation is. Using the existing stream elevation is not always useful because the groundwater levels may be above or below the existing stream levels. Additionally, you will need to know the ground water fluctuations over the growing season. Typically, streams and groundwater are highest in spring after run-off and lowest in late summer/fall. Wetland specialists and engineers can help you determine the appropriate wetland elevation.
2. Soils (topsoil)
The type of soil affects what kind of wetland can develop on a site. A wetland specialist or your local NRCS office can help you determine your soil type (NRCS contact info at bottom of sheet).
• Sandy/gravelly soils – Vegetation may be difficult to establish in these soils without adding additional topsoil.
• Loams (sandy loam to clayey loam) – Loamy soils are the best growth medium for vegetation.
• Clay (loamy clay to clay) – Clayey soils can be a good medium for wetlands because they will hold water for longer periods of time. However, clayey soils may be high in salts – many plants cannot tolerate high salts.
3. Vegetation
What wetland plants will grow depends on the hydrology, soils and other conditions at your site:
• Some species (such as cattails and bulrushes) grow only in areas saturated or inundated during the growing season; others (such as foxtail barley and fowl bluegrass) can grow in areas that are periodically dry.
• Many wetland plants grow best in loamy soils. However, there are others that tolerate salty soils, such as saltgrass and alkali muhly. Others, grow in sandy soils, including sandbar willows and switchgrass.
• Many wetland plants do not grow well from seeds, including most sedges and rushes; they grow best from plugs. Some plants grow easily and quickly from seeds, including Canada wildrye and other grasses. Wetland tree and shrubs, such as alders and willows should be grown from cuttings or containerized plants.
A groundwater sampling device such as a “piezometer” can measure the groundwater level at multiple times during a growing season.
You can find out more about evaluating wetlands in the Wetlands section of Chapter 2
NRCS Office Contact Information
Longmont Field Office
Boulder County (Boulder Valley CD-709, Jefferson CD-739, Longmont CD-743)
9595 Nelson Road, Box D
Longmont, Colorado 80501-6359
Ph: 303-776-1242
Fort Collins Field Office
Larimer County (Fort Collins CD-730, Big Thompson CD706, Home Supply Watershed Project)
150 Centre Ave., Bldg. A, Ste. 116
Fort Collins, Colorado 80526-8121
Ph: 970-295-5656
Greeley Field Office
4407 29th St., Suite 300
Greeley, Colorado 80634-9519
Ph: 970-356-8097