Maps, Forms & Glossary


In the Waterfront Navigator glossary, we’ve compiled regulatory terms and definitions from agency documents, environmental terms you will come across when doing work in wetlands and in coastal areas, and abbreviations used by agencies or on this site. Definitions cite the sources, with links back to original documents or websites for further reference.

Lead agency

The agency principally responsible for carrying out, funding, or approving an action; therefore, the agency responsible for determining whether an environmental review is required. (NYC Mayor's Office of Sustainability)

Littoral zone (LZ)

The tidal wetlands zone, designated LZ on an inventory map, that includes all lands under tidal waters which are not included in any other category, except as otherwise determined in a specific case as provided in [6 CRR-NY 661.16]. Provided, there shall be no littoral zone under waters deeper than six feet at mean low water. Pending determination by the commissioner in a particular case, the most recent, as of the effective date of this Part, national ocean survey maps published by the national ocean survey, national oceanic and atmospheric administration shall be rebuttable presumptive evidence of such six foot depth. (New York State Department of Environmental Conservation)

Loss of waters of the United States

Waters of the United States that are permanently adversely affected by filling, flooding, excavation, or drainage because of the regulated activity. Permanent adverse effects include permanent discharges of dredged or fill material that change an aquatic area to dry land, increase the bottom elevation of a waterbody, or change the use of a waterbody. The acreage of loss of waters of the United States is a threshold measurement of the impact to jurisdictional waters for determining whether a project may qualify for a Nationwide Permit; it is not a net threshold that is calculated after considering compensatory mitigation that may be used to offset losses of aquatic functions and services. The loss of stream bed includes the linear feet of stream bed that is filled or excavated. Waters of the United States temporarily filled, flooded, excavated, or drained, but restored to pre-construction contours and elevations after construction, are not included in the measurement ofloss of waters of the United States. Impacts resulting from activities eligible for exemptions under Section 404(f) of the Clean Water Act are not considered when calculating the loss of waters of the United States. (US Army Corps of Engineers, 2012 Nationwide Permits, Conditions, and Definitions)


See term: Docking Facility

Mean high water line/mark (MHWL)

The line on the shore in tidal areas established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding area. (US Army Corps of Engineers New York District, Regulatory Program Applicant Information Guide, 2014)

Mean low water (MLW)

Average height of the low waters over a 19-year period. For semidiurnal and mixed tides, the two low waters of each tidal day are included in the mean. For a diurnal tide, the one low water of each tidal day is used in the mean. Mean Low Water has been used as datum for many navigation charts published by the National Ocean Survey, but it is being phased out in favor of Mean Lower Low Water for all areas of the United States. (US Army Corps of Engineers, Low Cost Shore Protection: A Property Owner's Guide, 2004)

Mitigation (Compensatory)

The restoration (re-establishment or rehabilitation), establishment (creation), enhancement, and/or in certain circumstances preservation of aquatic resources for the purposes of offsetting unavoidable adverse impacts which remain after all appropriate and practicable avoidance and minimization has been achieved. (US Army Corps of Engineers, 2012 Nationwide Permits, Conditions, and Definitions)

Mitigation bank

Mitigation bank means a site where wetlands and/or other aquatic resources or natural habitats are restored, created, enhanced, or in exceptional circumstances, preserved, expressly for the purpose of providing compensatory mitigation in advance of authorized impacts to similar resources. For purposes of the Clean Water Act, Section 404 (33 U.S.C. 1344), use of a mitigation bank can only be authorized when impacts are unavoidable. (Electronic Code of Federal Regulations, Title 23, Part 777, March 2016)