Wetlands and nonpoint source pollution have a complex relationship. Wetlands are intricate ecosystems that have attributes of other waterbodies and upland areas. Wetlands naturally perform pollution prevention and treatment functions, but are also protected by state, federal, and in some counties, local laws and regulations. Using engineering and science, we have found ways to replicate the functions of wetlands and use constructed wetlands to clean up water from both point and nonpoint sources. This guide is meant to orient you to the key concepts and issues regarding wetlands and nonpoint source pollution.
Note: We strongly recommend consulting with program staff before beginning the process of planning and designing a wetland best management practice.
Wetlands are an important ecosystem in Indiana. The Indiana Department of Environmental Management (IDEM) regulates wetlands under state and federal law, and has a comprehensive website that provides definitions, wetland functions, the extent of wetlands, and other useful information. Most importantly, the website details the federal regulatory program and state regulatory program that protect these resources.
Wetlands that are covered by these programs cannot, under any circumstances, be used to treat point or nonpoint source pollution.
Wetland Best Management Practices - Terminology
It is possible to replicate the functions of natural wetlands in an engineered setting. A constructed wetland is a wetland restored or created in order to treat some form of point or nonpoint source pollutant. Constructed wetlands differ from natural wetlands in that they are specifically designed to treat certain types of pollutants. In addition, constructed wetlands are not regulated by state and federal laws. It is important to note that constructed wetlands are not “mitigation wetlands”, that is, wetlands created, restored, or enhanced to replace wetlands impacted by the placement of dredged or fill materials. Mitigation wetlands are requirements of state and federal permits and are considered to be waters of the state.
A number of terms are used in the world of wetland best management practices and wetland restoration. To help you understand how IDEM’s nonpoint source grant program views wetlands, the following definitions are listed below. These definitions only apply to IDEM’s nonpoint source grants program - note that federal and state regulatory programs may define wetlands differently. These definitions do not supersede definitions found in state or federal statutes and regulations.
A wetland developed by the manipulation of the physical, chemical, or biological characteristics present to develop an aquatic resource that did not previously exist at an upland site. Creation results in a gain in aquatic resource area and functions.
A wetland developed by altering the physical, chemical, or biological characteristics of an aquatic resource to heighten, intensify, or improve a specific aquatic resource function(s). Enhancement results in the gain of selected aquatic resource function(s), but may also lead to a decline in other aquatic resource function(s). Enhancement does not result in a gain in aquatic resource area.
A wetland which has zero surface water connections to a Water of the State.
A wetland where nearby actions have removed a threat or prevented the decline of an aquatic resource. Preserving wetlands also includes activities commonly associated with the protection and maintenance of aquatic resources through the implementation of appropriate legal and physical mechanisms. Preservation does not result in a gain of aquatic resource area or functions.
A wetland developed by manipulation of the physical, chemical, or biological characteristics of a site with the goal of returning natural/historic functions to a former or degraded aquatic resource. Restoration is divided into two categories: reestablishment and rehabilitation.
The manipulation of the physical, chemical, or biological characteristics of a site with the goal of returning natural historic functions to a former aquatic resource. Reestablishment results in rebuilding a former aquatic resource and results in a gain in aquatic resource area and functions.
The manipulation of the physical, chemical, or biological characteristics of a site with the goal of repairing natural historic functions to a degraded aquatic resource. Rehabilitation results in a gain in aquatic resource function, but does not result in a gain in aquatic resource area.
Wetland Best Management Practices – Resources
The following are examples of wetland best management practices, specifications, and supplementary information. These are provided as a guide – individual project planning and design utilizing soil scientists and wetland experts that are familiar with your watershed is a must in order to insure compliance with existing laws and to have a successful practice designed and installed.
- Best Management Practice Fact Sheet 11: Wet swale [PDF] (Virginia Cooperative Extension)
- Constructed Stormwater Wetlands [PDF] (Charles River Watershed Association - MA)
- Post Construction Stormwater Practices [PDF] (Indiana Stormwater Quality Manual - IN)
- Protecting Natural Wetlands - A Guide to Stormwater Best Management Practices [PDF] (U.S. EPA)