Technical 1 By Rebecca McMackin
Dealing with salt When we think about storm damage, we do not always think of how to mitigate the damage that salt inflicts on plants. But for the director of horticulture at Brooklyn Bridge Park this was a major concern in the aftermath of Hurricane Sandy.
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n October 2012 Hurricane Sandy devastated coastal regions of New York and New Jersey. Much of Brooklyn Bridge Park (BBP) was underwater for four hours. Sandy was the second ‘100 year storm’ in two years, and researchers at MIT say we should now expect such extreme weather events every three to 20 years. In light of our changing climate, robust ecological landscapes must now comprise more than native plants, sustainable construction, and organic management practices. Landscapes should be created with rising waters and extreme weather events in mind, and management practices for storms and floods should be researched, established, tested, and shared. Below is a case study for horticulturallyfocused storm management, using BBP’s experiences and experiments after Hurricane Sandy. The techniques utilised might be helpful in other coastal or storm-prone landscapes. Management strategies and (very) preliminary 46
Landscape Autumn 2013
experiment results are laid out below with the hope that other landscapes might benefit from and join the conversation about how to manage horticultural storm damage in the future. Assessing the storm damage Brooklyn Bridge Park is an 85-acre (34 ha) public park built on reclaimed shipping piers along the East River. The park contains many distinct ecosystems – from meadows to forests to wetlands – and is managed with an emphasis on ecology. While our many piers were hit hard by Sandy, the park weathered the storm relatively unscathed. Large areas of the piers, uplands, and even surrounding streets of the park were submerged in brackish and salt water for up to four hours during the storm. The park lost electricity that BBP is still working to restore (editor’s note – this article was first published in January 2013), and two playground surfaces were badly damaged. Three young trees toppled over, and anything that wasn’t secured, from 200-gallon (900 litre) planters to shipping containers, floated incredible distances around the park. However, that was the extent of the damage. While it is too soon to tell if submerged plant material will return with full vigour in the spring, initial surveys indicate minimal plant loss and we are cautiously optimistic. We owe this adaptability to forward-thinking park design and proper management in the
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days and weeks after the storm. The designers of the park, Michael Van Valkenburgh Associates (MVVA), carefully considered waterfront location, shoreline conditions, climate change, and rising sea levels to create a park capable of withstanding storms and major floods. Topographical changes blocked incoming flood waters, soft edge treatments of rip-rap and salt marshes held up against violent water forces, and the park itself soaked up waters that might have damaged the surrounding neighborhoods further. The sandy soil profiles used in the park (between 70 and 90%) helped the initially salty soils drain quickly. Plants were selected for salt tolerance and placed with rising water levels in mind, using many salt tolerant natives like pitch pine, beach plumb, and Baccharis in flood zones. It is this kind of design sophistication that can help create the adaptable and climatechange-appropriate landscapes of the future. However, proper post-storm landscape management can be just as critical for ensuring long term plant survival. Flushing out the salt Following the storm and after four hours of salt water inundation, our biggest horticultural concern was flushing soils of plant-toxic salts. Remember Carthage? Elevated salt levels can kill plants through reverse