Background

In recent years, new information has come to light concerning the immediate, secondary, long-term, and cumulative adverse impacts associated with stream channelizations within our Regulatory District. In response, we have adapted a more rigorous review of stream channelization applications. 

Channelizations tend to (among other things) increase sediment loads and turbidity, as well as downstream bed and bank erosion, sedimentation, and flooding; cause upstream down cutting, lower groundwater tables, reduce or adversely impact fish and wildlife habitat, drain wetlands, and warm water. Channel straightening projects also can threaten bridges (and other infrastructure) upstream and downstream due to the potential for downstream erosion and upstream down cutting as the channel works to re-establish its previous slope. Projects can significantly reduce the existing channel length, while greatly increasing the channel slope, maximizing the adverse effects described above.

Alternatives which are less damaging to the aquatic resource should be considered in place of channelization. Those alternatives may include armoring the affected stream banks within the project area with quarry rock or broken concrete riprap to abate further channel movement, the excavation of accumulated sediments from the existing channel (without altering the existing alignment), cutting back channel banks to establish more stable side-slopes, and the establishment of vegetative buffers along the creek.

Any person, business, or agency proposing to impact existing streams must first make every attempt to avoid and minimize the impact. For the impacts that are unavoidable, the replacement of any loss is required through compensatory stream mitigation overseen by the U.S. Army Corps of Engineers. In general, foot-for-foot stream length replacement will be required as mitigation for stream impacts. The below stream mitigation methods and calculators are tools that can be used to determine necessary stream mitigation. The Corps will coordinate with applicants to make a final determination as to the amount of stream mitigation necessary.  

What Is Compensatory Stream Mitigation?

Unavoidable impacts to streams are compensated for by the restoration and protection of another stream – referred to as a stream mitigation bank. This is part of a set of standards implemented by the U.S. Environmental Protection Agency (EPA) and the Corps of Engineers to promote "no net loss" of aquatic resources.

What Is a Stream Mitigation Bank?

A stream mitigation bank is a stream site that has been restored and protected by formal agreement between the Corps of Engineers and the stream mitigation bank sponsor. This agreement includes construction and monitoring standards to ensure quality and performance of the stream mitigation bank site. A stream mitigation bank sponsor may be a government agency, non-profit organization, or corporation. The Corps, in cooperation with other Federal, state, or local agencies, determines the amount of environmental credits a stream mitigation bank can provide. Mitigation credits are then used to offset environmental impacts from projects permitted by the Corps under Section 404 of the Clean Water Act.

The Stream Mitigation Process

Any entity proposing a project that impacts an existing stream must be permitted to do so by the Corps of Engineers based on regulations put into place under of the Clean Water Act, which may require compensatory stream mitigation. One method to satisfy this requirement is to purchase environmental credits produced by a stream mitigation bank. The Corps determines the amount of credits an applicant must obtain, which is stated in the conditions of the permit. Other methods to satisfy this requirement are in-lieu fee mitigation or permittee-responsible mitigation. These methods may be used when mitigation banks are not available.