Association of State Wetland Managers - Protecting the Nation's Wetlands.

The Wetland Wanderer: Insights on Low Impact Development (LID) as Part of Stream Mitigation

by Brenda Zollitsch

On April 30, 2014, ASWM published its Report on State Definitions, Jurisdiction and Mitigation Requirements in State Programs for Ephemeral, Intermittent and Perennial Streams in the United States.  ASWM interviewed state staff working on stream mitigation in forty-seven states.   ASWM’s report offers many Channelized stormwater runoffinsights into how mitigation of impacts to streams is rapidly changing across the country.  One of the findings of the report is growing consideration of low impact development (LID) as part of the avoidance, minimization and mitigation sequence for 404 permits and 401 water quality certifications.

A rich and growing body of literature and reports provide compelling evidence that development patterns based on conventional zoning codes result in sprawl.  Imperious surfaces Installing Conventional Stormwater Infrastructurethat are part of conventional development prevents water from supporting nearby wetlands and streams with base flow, limit the replenishment of groundwater supplies, and convey polluted runoff to streams, wetlands an d other waterbodies[1].  In order to deal with polluted stormwater that runs off of these sites, structural controls such as catch basins, pipes, and detention ponds are used. These techniques themselves often lead to the introduction of non-native plants, overuse of herbicides, pesticides and fertilizers, and excessive water consumption.

An alternative to this conventional approach is Low Impact Development (LID), which EPA describes as “an approach to land development or re-development that works with nature to manage stormwater as close to its source as possible. LID employs principles such as preserving and recreating natural landscape features, minimizing effective imperviousness to create functional and appealing site drainage that treat stormwater as a resource rather than a waste product” (ibid).  LID is often realized through a combination of careful advance planning and the implementation of techniques such as bioretention, green roofs, rain gardens, grassed swales, permeable pavers, rain barrels and cisterns, soil amendments, and treebox filters EPA states that “by implementing LID principles and practices, water can be managed in ways that reduce the impact of built areas and promotes the natural movement of water within an ecosystem or watershed.  Applied on a broad scale, LID can maintain or restore a watershed’s hydrologic and ecological functions” (ibid).

In ASWM’s interviews with state staff knowledgeable about stream mitigation issues in forty-seven states, we found that consideration of LID as a potential part of mitigation activities is on the rise.  However, other states have a decidedly different perspective.  They report that they reject LID in any amount or in any combination with other mitigation activities as a way to meet part of the mitigation sequence.  At least one state embraces it wholeheartedly as a key approach to improving infiltration and reducing polluted runoff into their state’s streams and wetlands.  Many other states are just starting to think about LID in relation to the 404 mitigation sequence and a good number report that they have no intention of allowing LID in any form in the near future.

Porous Pavers Allow Rainwater Infiltration at a Car DealershipThose states which use LID to address 404/401 requirements, indicated a wide array of approaches to its use.  Some states shared that LID has been included in state stream mitigation programs as part of a broader mitigation package that includes out-of-kind LID mitigation as part of approved mitigation activities.  Others reported that LID is being seen as a way to contribute to overall improvements in stream functions.  And yet others view LID as part of minimization in the avoidance-minimization-mitigation sequence (rather than mitigation).  Most compellingly, at least one state in the Chesapeake Bay region reported that accepting LID (even in cases where it was also being counted for NPDES) was a critical and growing approach to addressing the states severely impaired watersheds.

Embedded swale in a housing complexReview of the interviews found, not surprisingly, that there is little consistency in how states approach consideration of LID in mitigation programs.  However, many interviewees shared that they are interested in seeing how other states deal with the LID issue.   At the national, regional and state level, it may be useful to identify circumstances and locations where LID approaches can be especially effective for stream and/or wetland mitigation and where they are not.  A starting point might be developing case studies of “LID as mitigation” success stories.  Because LID as a mitigation activity is not commonly adopted, it may prove useful to develop a dialogue to identify appropriate criteria for using LID, barriers to implementation and ways to overcome them.  Finally, as with many areas of knowledge and network building, there is a need to build bridges between the stream mitigation and stormwater management staff in states that are interested in exploring opportunities to integrate LID into mitigation plans.

ASWM’s stream report identifies a nascent practice of connecting the dots between mitigation and stormwater management.  Part of this practice includes potentially addressing stream impacts through, in part, the use of low impact development techniques.  We look forward to hearing from you about examples, opportunities, barriers and resources that ASWM can share with states as they explore how to most effectively address dredge and fill impacts to streams in the United States.

To Learn More:

To download ASWM’s Stream Report, go here.

For more links to stream mitigation resources, visit ASWM’s stream mitigation webpage here.

For more information about low impact development, go here.


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