The data, maps, and information in Version 2 of this mapping tool are provided to illustrate the scale of potential flooding in New York's Hudson River Valley and the Westchester County shoreline along the Long Island Sound under multiple sea level rise and storm tide scenarios (five year–1,000 year return).

Flood events are modeled with the New York Harbor Observing and Prediction System (NYHOPS) in the Hudson River, and mapped out onto the surrounding floodplain using a "bathtub" methodology. Water level (also known as still water elevation) estimates produced by the modeling effort are subtracted from the 2011–2012 New York State Department of Environmental Conservation's LIDAR dataset in order to produce flood depth estimates. The sea level rise scenarios available within the tool range from 0 to 6 feet above the base mean sea level of 1983–2001, a standard sea level used by the National Oceanic and Atmospheric Administration.

A set of impact estimates accompany each of the flood scenarios presented in the mapping tool. The impacts are divided into three themes: critical infrastructure, social vulnerability, and natural resilience features:

• Critical infrastructure impacts are estimated at the municipal level and composed of loss estimates derived from the HAZUS-MH 2.2 Flood Model, as well as counts of affected facilities, landmarks, and physical features.
• The social vulnerability information is summarized at the municipal and block group levels and was derived from a social vulnerability index produced from U.S. Census 2010, and American Community Survey data.
• The information on natural resilience features was produced by calculating inundated and total land areas for several variables important for conservation and stormwater amelioration.

The tool provides downloadable estimates of flooding impacts for each flood scenario, including affected population and critical infrastructure and cost estimates of building damage, and of the underlying GIS data.