Wetlands have been called the kidneys of the landscape. They filter out sediments from surface water runoff and absorb nutrients, heavy metals, and other chemicals from runoff. Wetlands also act to replenish groundwater and as retention basins that assist in reducing flooding. During major rain events wetlands hold water for days or weeks allowing the water to slowly filter into the ground or drain into streams and rivers.
Wetlands are particularly important to wildlife because they provide food and cover for many wildlife species. For migratory waterfowl, shorebirds, wading birds, and passerines, wetlands provide vital links as resting and feeding areas which connect animals with their breeding and overwintering grounds. The reproductive potential of many migratory wetland birds is influenced by the availability and quality of these stopover wetlands. When quality wetland habitat is available migratory wetland birds arrive at their breeding grounds in healthier condition if they sufficient feeding and roosting areas along the way. These seasonal wetland habitats that provide this needed feeding and roosting sites are in short supply across much of the United States.
Wet meadows have water depths of less than 6 inches for an extended period during the growing season. Vegetation consists primarily of grasses and sedges. Forbs such as blue vervain, swamp milkweed, Joe Pyeweed, jewelweed, and boneset can also be found. Annuals such as beggar's tick, and smartweed commonly pioneer disturbed areas and mud flats.
Emergent wetlands have water depths from 6 inches to 2 feet. Emergent wetlands contain water for much of the growing season, but shallow areas may become dry during drought periods. Shallow emergent wetlands often have open water mixed with vegetation such as cattail, bulrush, arrowhead, bur reed, and water plantain.
Open water wetlands or deep water marshes have water that is greater than 2 feet in depth and often contain water for an extended period during the growing season. Deep water marshes are primarily open water and are sparsely vegetated with floating and submergent plants such as water lily, lotus, and pond weed. Deep water marshes are not pond and lakes.
Shrub/scrub swamps usually contain 6 in to 24 in of water during the growing season. They are dominated by shrubs such as silk dogwood, red osier dogwood, buttonbush, alder, willow, and elderberry and hardwood trees less than 15 feet tall. These areas are often transition zones between emergent wetland and forested wetlands. Decaying leaves provide substrate for invertebrates that provide food to a variety of wetland dependent wildlife species. The primary value of shrub/scrub swamps for many wildlife species is as protective cover.
Forested wetlands are typically found in bottomlands in the floodplains of rivers and streams, but can also be found on upland sites where topography and soils do not allow water to drain. Soils may be saturated or ponding may occur and they are often seasonally flooded. Along rivers and streams these areas are often called Bottomland Hardwoods because they are dominated by flood tolerant hardwoods such as oaks, maples, and ash. Bottomland hardwoods are important to a variety of wildlife species including wintering waterfowl, frog, snakes, salamander, and a variety of bird species.
Upland forested wetlands are often called flatwoods as the area is often relatively flat and contains an impermeable layer which limits drainage. These areas often have depressions which fill with water during wet periods and are dry during dry periods of the year. Soils may be saturated for several weeks during the early growing season and during the winter. Upland forested wetland areas often are composed of oaks, hickories, ash, and maples. Herbaceous layers include sedges, bushy bluestem, vervain, beggar's tick and various other native wildflowers and grass.
A single wetland area may be composed of two or more wetland types. Such a composite is called a wetland complex. A wetlands complex provides the best habitat for many wildlife species because it allows those species to meet there needs with in a small area. When developing a wetland plan a good goal is to provide a mix of forested wetland, scrub/shrub swamp, emergent wetland, open water, and wet meadows. Within an emergent wetland the creation of a hemimarsh where 50 percent has plants and 50 percent is in open water provides more habitat for wildlife than only vegetated or only open water. A combinations of vegetation types will create different levels of plant succession in the wetland complex creating a high diversity of habitats and allowing more wildlife species to use it.
Site selection is very important in doing a wetland restoration versus a wetland construction. A wetland restoration typically occurs on areas where a former wetland occurred. These areas often have a slope of <2% with hydric , poorly drained, or somewhat poorly drained soils. Soils are often silt loam, silt clay, or clay soils. This information can be found by talking with your county Natural Resources Conservation Service (NRCS) office or looking at soils map at Web Soil Survey. Restoration sites tend to be areas that man has altered through ditching or tiling to remove water from an existing wetland. Typically these conditions are found in crop fields or pastures where landowners have drained the field in order to grow crops , hay, or raise livestock. These areas may still contain small wet areas with wetland plants, but the true function of the wetland has been removed. Wetland restoration can also occur in forested areas as some forested wetlands were also drained in order to " better the land". This bettering of the land had various reasons from getting rid of disease to snakes and other issues associated with "swamps".
Site selection for a constructed wetland is often much different than a wetland restoration. Constructed wetlands can occur on ground that has a slope up to 5% and does not contain hydric or poorly drained soils. In constructed wetland the soils often have high clay or silt content that can be excavated and compacted to create a basin that will hold runoff. Constructed wetlands tend to be more expensive to create because of the amount of earth work that needs to be done.
When planning your wetland you will need to determine if the water source of the wetland. This is extremely important because without a water source your wetland becomes just a dry hole. A surface water wetland holds rain water like a bowl. When it rains runoff from surrounding uplands drains into the impermeable surface of the wetland bowl that has been created. A groundwater wetland is like a well that is close to the surface. Groundwater close to the surface is exposed through excavation of the wetland. In your proposed wetland site dig several small holes at least 3 ft deep. If the holes fill with water then you can create a groundwater fed wetland. If the hole is dry you will need to develop a surface water wetland. A surface water wetland is created by compacting silt and clay rich soils in the wetland basin in order to create an impermeable layer for the water to collect in.
Before undergoing a wetland construction or restoration you will need to determine what permits are needed. A section 404 permit may be required by the U.S. Army Corps of Engineers in order to comply with the Federal Water Pollution Control Act of 1972. If required to get a section 404 permit you project may either fall under a Nationwide Permit 27 (NWP 27) or require you to apply for an individual permit. In order to receive approval under an NWP27 your project will need to be restoration of an artificial wetland or creation of a new wetland. If it is determined that your project is actually altering an existing natural wetland then you will be required to apply for an Individual Project Permit.
If your project occurs in the floodplain of a stream or river you may be required to get a Section 401 Permit from the U.S. Army Corps of Engineers and a Floodplain construction permit from your state division of water before restoring or creating a wetland in this area. These permits are required before placing, filling, installing culverts, building dams or creating small impoundments on land that may be flooded every 100 years.
If your project is receiving federal funding through NRCS, state agency, or U.S. Fish and Wildlife Service your consulting biologist will be able to help you with obtaining permits and what is needed. With federal funding additional approvals are often needed. These include Cultural Resources Surveys which must be approved by the State Historic Preservation Office (SHPO) in order to protect potential archeological resources that may occur where you plan to build your wetland. This cultural resources survey is required of any project that receives federal funding through the National Historic Preservation Act of 1966 (NHPA).
With federal funding you will also need to get approval from the U.S. Fish and Wildlife Service which is responsible for administering the Endangered Species Act. The U.S. Fish and Wildlife Service will through a site visit and paperwork you supply make sure that you project will not adversely affect federal threatened and endangered species. The restoration and construction of wetlands will provide needed habitat for many federally protected species therefore unless the wetland threatens some very site specific threatened or endangered species the U.S. Fish and Wildlife Service is very willing to help make your project successful and is not looking to delay its implementation.
Although restoration or construction of a wetland is not difficult, it is highly recommended that you consult with a biologist or NRCS office for technical assistance with the design of your wetland project. These resources can help with identifying proper location, potential funding sources, permit needs, and design of the wetland complex.
The equipment needed in construction or restoring your wetland will depend on the size of the wetland and where the wetland is being constructed. Small wetlands can be constructed with a small backhoe while large wetlands may require a large dozer, backhoe, drag pan, and/or soil compactor.
In many wetland construction situations a dike, levee, or dam will need to be constructed. A dike or dam should have a profile or slop of 10:1 or 12:1 with a top 8 to 14 feet wide. When constructing the dike all trees, brush, and organic soils should be removed from the dam site. A core trench or key should be dug the length of the dam as wide as the dozer blade or excavator. The core or key trench should be dug until an impermeable layer such as solid rock or a clay layer is reached. The purpose of the core or key trench is to keep water from seeping under the dam. The dike core should be back filled with clay or a silt clay mix that can be compacted in order to form an impermeable seal.
Non-organic soils for construction of the dike are typically removed from areas within the wetland. The areas that are dug out can be used to create micro-topography within the wetland itself. These dugout areas or borrow areas can be from 6 inches to several feet deep. When the wetland is flooded these borrow areas will create deeper open water. The borrow area typically will be located close to the dike because it is too difficult and expensive to move large quantities of dirt very far with a dozer. If a scraper or loader and dump truck are used then the borrow areas can be created throughout the wetland in order to create shallow areas intermixed with deeper areas.
An emergency spill way should be constructed away from the dike. By constructing the emergency spillway in soil away from the dike, it will reduce the potential for erosion during high flow events to damage the integrity of the dike. Emergency spillways should be constructed in order to handle at least a 100 year flood event and lined with rip rap or key erosion points should be rip rapped and remaining area seeded to native grass. In floodplains it may be better to construct riprapped key overtop areas above the normal pool level on the dike which limit erosion and allow water to flow over with in specific areas rather than the entire dike. By allowing these fortified key overtop areas to channel water, damage to the dike may be reduced or eliminated.
Another way to create a wetland or create topography with in a wetland complex particularly on flat or areas with < 1% slope is to use a dozer or scarper to dig out shallow bowls. The bowls are scraped out and the soil is scattered near the edge of the wetland creating irregular soil mounds throughout the wetland. These bowls and mounds create micro-topography which can act as loafing and nesting sites for a variety of wildlife. It also helps create varying depths of water throughout the wetland complex.
Water control structures have their pluses and minuses when it comes to us in a wetland restoration or construction. Water control structures allow you to manipulate water levels so that you are able to mimic natural wetland processes, manage vegetation within the wetland complex, create mud flats for shorebirds, and plant floodable crop areas for migratory waterfowl.
The minuses of water control structure include the pipe if not properly installed can allow water to seep out of the wetland. In areas prone to beaver activity special precautions need to be made in order to keep beavers from damming up the control structure which ultimately may result in overtopping of the dike and structural damage. Depending on the material and type used water control structures may fail over time resulting in expensive repairs in the future. Steel pipes may rust through over time. If not laid properly aluminum piping can be crushed or damaged. Plastic pipe can be crushed or cracked during installation and certain grades of plastic pipe deteriorate when allowed to be exposed to sunlight for long periods.
Water control structures can include stoplog, screwgate, or a simple adjustable pipe riser. Stoplogs can be enclosed or partially open. A stoplog control structure consists of slates or logs which fit into grooves and by adding or removing the slates you are able to control water level from 6 to 12 inches per slate. Screwgates are operated like a spicket or faucets which by opening or closing you are able to control the amount of water held in the wetland complex. The simplest water control structure can be made of steel, aluminum or plastic pipe and consist of screwing or slide in pipe sections. An elbow or T is used on one end with a vertical length of pipe used to control the depth. A longer the longer the piece of vertical pipe the deeper the wetland.
When running pipe through a dike an anti-seep collar should be used. Anti-seep collars act to keep water from following the pipe through the dike and over time eroding soil around the pipe creating a leak. An anti-seep collar is place before and after the area near the key trench. Anti-seep collars can be made of flat rubber sheets that the pipe goes through or can be created using concrete.
Moist soil management is the management of native wetland plants such as smartweed, ragweed, sedges, rushes, and other annuals which provide seed for waterfowl. Moist soil management mimics natures flooding and drying periods along with disturbance in order to provide numerous seeds from native moist soil plants and some naturalized non-native plants. Managers should set up a 2 to 4-year rotational schedule for disturbing moist-soil impoundments based on site specific objectives, capabilities, control of nuisance plants, and knowledge of the area. In order to properly manage for moist soil plants you will need to be able to keep the site wet throughout the growing season. If you drain the basin and allow it to stay completely dry through the growing season moist soil plant response will be limited.
Below are two possible options for managing a moist soil unit. Variations on these options can be done in order to control invasive plants like cockleburs, coffee bean, or to meet your wetland management objectives.
Early season drawdown followed by disking for moist soil plant production.
Slow drawdown in early to mid-season keeping soil moist for as long in the growing season as possible.
Early season drawdown or maintain shallow water throughout growing season.If shorebirds are of interest an alternative would be for a late summer drawdown then disking to provide habitat for fall migrating shorebirds.
Maintain 12 inch depth until July, then allow water to drop with evaporation and hold a shallow flood until winter or release any remaining water September 1 to disk if needed.
Early drawdown by March then close structure to catch rain fall or pump to flush impoundment. Flood October -December which will encourage wild millets.
Maintain 36 inch depth through the growing season and winter until the following July. This allows for recycling of plant material and encourages more invertebrate development and also provides more habitat for diving ducks.
Maintain 36 inch depth until June, then stagger drawdown for shorebirds, pump as necessary to maintain mudflats and reflood October. This flooding will benefit fall shorebird habitat by allowing mud flats to be maintained.
Video provided by Missiouri Department of Conservation.
Managing and flooding cropland for wintering waterfowl has been used for 40+ years in order to provide crucial nutrients to wintering waterfowl. This use of crop such as corn, soybean, milo, and millet was developed in order to make-up for the lack of native seeds and invertebrates which would typically be found in wetlands before drainage of critical wetlands occurred. Corn is often called a "hot crop" for waterfowl because it provides a high source of carbohydrates that can be readily used by waterfowl. However, corn lacks many or the essential nutrients needed by waterfowl and when submerged in water corn kernel rot relatively fast. Soybeans also have been used for providing protein and other nutrients for wintering waterfowl. However, soybeans can cause a number of issues with waterfowl. The beans when eaten can swell in the throat or crop of waterfowl causing the bird to starve to death. Soybeans when flooded rot quickly leaving very little food for waterfowl. The harder and more numerous seeds of milo and millet make a better crop food for waterfowl. Modern harvesting equipment are much more efficient and if a corn, soybean, or milo field is harvested before flooding very little waste grain is left.
One a alternative to corn alone is to plant "Dirty Corn". When planting "dirty corn", use 36 inch to 42 inch wide row spacing. After planting corn only control weeds long enough to give the corn seedlings a chance to grow above weeds. Typically this is within the first 3 to 4 weeks after seedlings germinate. Once the corn has grown above the weeds, allow weeds to again grow along with the corn. The wide spacing and limited weed control will allow sedges, barnyard grass, sprangletop, smartweed, ragweeds, and other potential waterfowl food sources to grow. When flooded the corn will provide early food for waterfowl while the "weeds" will provide food long after the corn has rotted or has been consumed. The corn stalks and "weeds" when flooded will also provide substrate for aquatic invertebrates to develop and grow providing additional nutrients for waterfowl.
Whether planting "Dirty Corn", standard corn, milo, or millet for waterfowl these crops should only be used in conjunction with moist soil management in order to better manipulate the "weed" seed found in your wetland complex. By planting a crop or manipulating the timing of flooding or draw down you will better be able to control what species grow and produce seed and control noxious seeds that have limited waterfowl value.
If you are fortunate enough to have a natural wetland such as emergent wetland or bottomland hardwood forest on your property then your management will be much different because you are unlikely able to control the water in the wetland. Although your first thought maybe to add your own water control structure to this wetland doing so can be very expensive. First you would need a permit from U.S. Army Corps of Engineers to do the work. However, it is highly unlikely that you would get a permit because your activities could damage the functionality of the wetland. Second depending on the site you may need specialized equipment in order to do the work. Your best opportunity is to work with what is already there. In the case of an emergent wetland you can add wetland plants such as arrow arum, arrowhead (duck potato), pickerelweed, bur reed, or soft stem bulrush. If the edges of the wetland dry out enough that you can lightly disk them during the summer you will be able to potentially stimulate the growth of sedges, bidens, barnyard grass, sprangletop, smartweed, ragweeds. These plants will benefit a number of wetland birds along with wintering waterfowl.
In the case of bottomland hardwoods, properly planned timber harvest may be what is needed. When doing a harvest in a bottomland hardwood you want to create openings in the tree canopy. These openings should be from 0.5 to 2 acres in size. Get additional information in our section on Forest Management. If you are interested in providing habitat for wintering waterfowl your timber harvest would be slightly different then if it was targeting a diversity of songbirds, snakes and salamanders. Timber harvest should favor leaving more mature hardwoods in particularly oaks like willow oak, pin oak, nuttal oak, and water oak. These oaks have much smaller and more plentiful acorns compared to the much larger swamp chestnut, swamp white oak and over cup oak. Clearing large areas with in the bottomland hardwood forest to plant crops is going to be expensive and provide minimal benefit.