Combining wetland restoration with stormwater management
Communities large and small rely on water sources. Development has been historically concentrated near water bodies to take advantage of this vital resource, yet constant use has led to deterioration of these fragile ecosystems. Wetlands, rivers, lakes, and streams are important to human health, but also act as health indicators of surrounding ecosystems. LEED for Neighborhood Development seeks to restore and/or enhance water bodies and adjacent areas through credits contained within the Smart Location and Linkage (SLL) credit category, including SLLp3: Wetland and Water Body Conservation and SLLc8: Restoration of Habitat or Wetlands and Water Bodies. Pursing these credits has far-reaching implications especially as it relates to Green Infrastructure and Building (GIB) credit 8: Stormwater Management. Conventional stormwater management through gutters and other impervious infrastructure inherently have problems, namely overflow and inability to filter out pollutants. These traditional systems concentrate and accelerate the flow of runoff, while the increasingly popular natural solutions such as bioswales and wetlands capture, purify, and slow runoff. Developers can use these two credits in tandem as restored wetlands and natural buffers offer long-term solutions to water runoff issues.
Hercules Bayfront in San Francisco, California and Navy Yard at Noisette in North Charleston, South Carolina are two certified LEED-ND pilot projects that distinguished themselves by combining these credits. Refugio Creek borders Hercules Bayfront and empties into San Francisco Bay. Wetlands next to Refugio Creek were restored beyond the minimum threshold specified in the credit improving not only the quality of water within the creek, but also the condition of the habitat, providing valuable nesting sites to birds that have historically foraged in these bayside wetlands. The developer connected this to stormwater management by committing to rainfall infiltration, reuse, and evapotranspiration on-site. The landscape features performing these services are considered bioretention measures and have the unique ability to filter out pollutants during a “first flush” event. This “first flush” is the initial rainfall that collects all of the pollutants that have accumulated on impervious surfaces, from silt to fertilizers, during a prolonged dry spell. These pollutants can choke fragile wetland habitats, filling with debris and leading to algal growth. Regionally adapted flora, detention basins, and bioswales contribute to on-site measures, leaving any additional purified runoff to collect in the wetland.
While the Noisette project site itself did not achieve the credit for a stormwater management plan, strategies contained with the Noisette Community Master Plan outline a community-wide system of swales to effectively direct runoff to the wetlands in Noisette Creek. The wetlands adjacent to the creek were also restored beyond the minimum area required and the city encouraged the use of native plants in adjoining community backyards, connecting previously fragmented habitat.
Both the Hercules Bayfront and Navy Yard projects earned SLLc8 by utilizing natural approaches, which ensures ecological health despite development pressures. The forward thinking involved in these projects mirrors the conceptual ethos of LEED-ND, looking beyond the building footprint to answer local environmental problems. This rationale is increasingly important in the face of more frequent and more severe storms, and rising sea levels. The most publicized example of similar efforts on a much larger scale is the call to soften the edges of Manhattan with natural features, like wetlands, following Hurricane Sandy. Plans are already underway and many coastal communities have the opportunity to make their waterfront more resilient following the guidelines set out in LEED-ND. Recognizing wetlands’ connection to stormwater management and continuing to replenish these fragile amenities stands in the best interest of communities facing pressures from a destabilized climate, as Hercules Bayfront and Navy Yard at Noisette have demonstrated.