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Local Watershed Statistics

Sponsored by the Connecticut DEP Office of Long Island Sound Programs

Each link below takes you to a web page with a map as well as a link to a pdf of the map (complete with layout) for printing.

2002 Percent Developed

The above maps are based on land cover coefficients to estimate imperviousness. This map shows, simply, the percent of the basin that is in the developed class according to the 2002 land cover.

1985 Impervious Surface Estimates

1990 Impervious Surface Estimates

1995 Impervious Surface Estimates

2002 Impervious Surface Estimates

The Impervious Surface Analysis Tool (ISAT) was used with each of the 1985, 1990, 1995 and 2002 land cover along with a set of derived coefficients in order to estimate impervious surface area for each local watershed in Connecticut. The Impervious Surface Section of the NEMO website discusses a number of methods for mapping imperviousness. The section on ISAT describes this method and links to the NOAA website where you can download the ISAT as well as a link to the coefficients derived for the Connecticut land cover.

Increase in the Impervious Surface Estimate from 1985 to 2002

This map shows results from a comparison of the impervious surface estimate for 1985 and the estimate for 2002. Basins are colored based on the amount of increase in imperviousness over the time period.

Basins Crossing Critical Impervious Surface Thresholds of 10% and 25%

Research on imperviousness and water quality has determined two critical thresholds. When a basin passes from less than 10% imperviousness to over 10% imperviousness, the water quality is impacted. When a basin passes from less than 25% imperviousness to over 25% imperviousness, the water quality becomes degraded. The map shows those basins in Connecticut that have crossed one of these two critical thresholds between 1985 and 2002.

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