Managing in a Floodplain

Many different tools and techniques are used in the management of a wildlife refuge. Although we attempt to restore and manage the entire ecosystem so that natural processes can occur, ecosystem management does not mean "hands off." In modern floodplains, it is necessary to work with erosion, sedimentation, and the flood cycle in an attempt to manage and guide these processes to mimic the former natural system.

Using historical records of the pristine Illinois River as a guide, we use a "mitigative management strategy" to promote wetland-dependent plant communities and wildlife populations. Plant and animal species evolved to depend on the pristine structure and function of the river-floodplain relationship. Each plant community has a specific moisture tolerance and occupies its own niche, which is influenced or even dictated by, the water regime. Human modifications to the structure of the floodplain, such as navigation locks and dams, stream channelization, the diversion of Lake Michigan water, and agricultural levees, ditches, and field tiles, have changed the floodplain function. With these changes have come changes in the diversity, abundance, and general health of plant and animal communities.

 

 

Chautauqua National Wildlife Refuge is managed to mimic the historic flood cycle, a strategy which creates the conditions necessary to support native plant and animal communities that are reminiscent of a large river-floodplain ecosystem. We attempt to mitigate the human-induced changes to the flood cycle in order to promote biological diversity, stability and resilience in an altered system.

Moist Soil Management 

 
When mud flats are exposed by summer drawdowns of water levels moist soil plants develop. These plants have the potential to produce high seed yields that serve as an important food source for waterfowl and other wildlife. Compared with grain from agricultural fields, moist soil plants contain a better balance of nutrients.  

A diversity of invertebrate and vegetative foods from different wetland types are needed on fall and spring migration areas to meet the changing nutritional demands of waterfowl and provide them with a complete diet.
Many refuge wetlands are equipped with water control structures that allow the manipulation of water levels. This manipulation permits biologists to control the summer drawdown of water levels in a way that provides optimum moist soil plant growth. Water levels are slowly increased in the fall to provide the desired mix of open water and mature flooded moist soil vegetation.

Wetland Restoration 

 
Restoring wetlands is often simply a matter of destroying manmade drainage facilities and letting water and vegetation return to the site naturally. The same tools used to destroy wetlands are used to restore them. If a wetland is drained by underground tile, a section of the tile is uncovered, removed, and the area is backfilled with soil. Wetlands that are drained by ditches are restored by the construction of an earthen ditch plug at the outlet to the wetland. A pipe or earthen spillway is used to regulate water levels and provide for overflow. On larger wetlands, a water control structure may be installed that allows a periodic drawdown of the wetland in an attempt to mimic the natural wet-dry cycle of many basins.

After restoration, wetland plants begin to reappear. The seeds of some wetland species can lie dormant, but viable, for as long as thirty years, waiting for moist conditions to return. These species will be among the first to appear after restoration, often even after years of agricultural herbicide use. Other seeds are carried into the wetland basin by birds, wind, and floods. It is generally not worth the cost to attempt to revegetate a wetland; if the conditions are right for a species, it will find its own way into the restored basin.

If you are interested in restoring a wetland on your property, check out our Partners for Fish and Wildlife program.

Prescribed Burning 

Prescribed burning is a tool used by land managers to provide many benefits. Burning reduces woody plant invasion and removes litter buildup in fields. Warm season grasses such as bluestem, switchgrass, and Indiangrass are stimulated by a properly-timed prescribed burn. When a burn is conducted in early April, cool season grasses have already begun to sprout, and will be badly damaged by the fire. However, warm season grasses are still dormant, and their underground energy reserves are unaffected.

The black ground that results from a burn increases soil temperatures, causing warm season grasses to sprout earlier, enabling them to compete with any cool season grasses that remain. Fall burning is not as effective because it allows cool season grasses to grow after the burn without competition. Burning may also be used to prepare a field for seeding by removing litter and other unwanted growth.