Using a Geographic Information System to Assess the Influence of Landscape Characteristics on Stream Turbidity in the Long Island Sound Watershed

Officials with the Long Island Sound Study (LISS) are presently reviewing the suite of indicators used to assess and report on Long Island Sound's ecological health and the programmatic success of the LISS. As part of this evaluation, managers seek to determine whether there are environmental variables that offer valuable information on ecosystem condition but that have not historically been tracked, or have not been utilized to their fullest potential. This paper reviews the use of ecological indicators by the LISS, explores the literature documenting relationships between land use/land cover and water quality and documents the use of a geographic information system (GIS) to perform an analysis of the impact that land use/land cover, slope and soil characteristics have on turbidity within the Long Island Sound (LIS) drainage basin. This paper then compares two models' ability to predict turbidity: the first model includes information on land use/land cover, slope and soil characteristics while the second accounts for soil characteristics. Although the land use/land cover-based model outperforms the soil parameters-based model in predicting stream turbidity, neither model's predictive ability is sufficiently strong to accurately forecast turbidity in the study area. These results are contrary to those documented in previous investigations. Further examination should be undertaken to determine whether an alternate methodology or inclusion of other relevant parameters would yield a more robust turbidity model.