Dewberry Innovation Case Study
Restoring an Urban River Bank and Uplifting a Community
Dewberry Engineers Help Rebuild, Revitalize New York City’s Harlem River Bikeway and Esplanade
When the New York City Department of Parks & Recreation (Parks) cut the ribbon to re-open the Harlem River Bikeway and Esplanade, the park’s revitalized waterfront bore little resemblance to its former, dilapidated state. Over the years, the constant pounding of waves and exposure to salt water had caused extensive corrosion damage to the existing steel sheet pile seawall. As the tide came in and out, water entering and exiting holes in the wall created a pumping action that removed soils and created sinkholes large enough to swallow newly planted trees and pavement. The park was unsafe, unappealing and inaccessible.
Dewberry Innovation in Action
Dewberry performed inspection as well as civil and structural engineering design services to reconstruct the public bikeway and esplanade between East 139th and East 145th Streets. In seeking the best solution for replacing the damaged seawall, Dewberry engineers began with the premise that structures existing where land and water meet must be designed to be complementary to - and protect - both.
Traditionally, seawalls were built to be either rigid (concrete) or semi-rigid (steel), reflecting wave energy rather than absorbing it. Dewberry explored a different path. Wave-tank testing at Stevens Institute of several “flexible” approaches revealed that a gabion wall - composed of porous metal baskets filled with stones – would provide the greatest mitigation against wave energy reflection, providing a turbulence-free shoreline. To guard against corrosion, the gabion baskets were built from 316-L saline-tolerant stainless steel and heat-fused together rather than welded. Another major benefit: a gabion wall allows for the introduction of marine-tolerant plantings while acting as a reef that attracts and promotes the growth of aquatic life.
Tide Pools, Cove Re-Engineering Create a Beautiful, Usable Public Space
Tests indicated that the addition of coves and setbacks would further reduce wave velocity and enhance the trapping of sediments. Dewberry’s inventive solution was to lower the gabion wall in two locations, allowing high-tide water to form publicly accessible tide pools that were surrounded by natural round stones. Additionally, Dewberry reengineered a sinking slope of broken concrete riprap using appropriately sized armorstones and granite blocks, creating steps and seating that allow the public to safely enjoy the river’s edge.
Dewberry helped Parks uplift the Harlem community by combining the design and ideas of community stakeholders to provide an environment that is safe and eco-friendly, with paths for walking, jogging and bike riding; tide pools for entertainment; and a cove for fishing and relaxation.