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ENVIRONMENTAL REVIEWS AND CASE STUDIES: Restoring a Salt Marsh in a Highly Urbanized Environment of New York City: The Alley Park Restoration Project

John H. Roebig^a1 c1, John K. McLaughlin^a2 and Michael J. Feller^a3

^a1 PhD, RLA, Senior Professional Associate, HDR, Inc., Pearl River, New York

^a2 Director, Office of Ecological Services Bureau of Environmental Planning and Analysis, New York City Environmental Protection

^a3 Chief Naturalist, New York City Department of Parks & Recreation, Natural Resources Group (NRG)

Abstract

The success of urban salt marsh restoration depends upon an understanding of the local tidal regime and hydrologic conditions. Reference wetland characteristics can provide biological and physical restoration baselines for a restoration design through the use of techniques such as bio-benchmarking and geomorphologic assessment. Reference site vegetation can be used as indirect indicators of local tidal elevations and duration of flooding of each tidal zone. Reference sites can also provide landscape allometry to generate geomorphologic ratios that can be applied to the restoration site. Through the use of field measurements, aerial photographs, and GIS technology, relationships can be identified for tidal channel width, depth, diurnal tidal prism, and marsh area. Calculating a hydrologic budget for freshwater is critical to estimate salinity concentrations and their effect on the restoration wetland. This information, along with field measurements of salinity, can be used to predict salinity ranges resulting from the interaction of freshwater sources and will help determine the target vegetation communities. Preconstruction planning is not always sufficient to understand site conditions, especially in urban areas. Flexibility in design, even during the construction phase, may be required to assure project success. During excavation of fill, conditions were found at specific locations that would reduce the likelihood of reestablishing historic functions and values of the tidal marsh. Designs were altered at one low marsh area, which was redesigned as mudflat; and a second low marsh area that was changed to a freshwater fen.

Environmental Practice 14:1–11 (2012)

(Received May 02 2011)

(Revised July 11 2011)

(Accepted September 24 2011)

Correspondence:

^c1 John H. Roebig, HDR, One Blue Hill Plaza, Pearl River, NY 10965; (phone) 845-735-8300; (fax) 845-735-7466; (e-mail) john.roebig@hdrinc.com, hdrinc.com