LAND USE INFLUENCES ON RGA SCORES AND RIVER CHANNEL WIDTHS IN NORTHERN NEW JERSEY

Shifts in land use, particularly urbanization, often affect the river channel morphology and flow characteristics. Changes in stream health and channel width have significant impact on local ecology, water quality and flooding. Urbanization creates an increased amount of impervious surfaces, which amplifies stream run off and consequently erosion. This project studied how two rivers in northern New Jersey responded to different land uses. As the rivers are similar in drainage area, stream order (5th), climatic conditions, and bedrock lithology, and are adjacent to each other, they can be paired in a space-for-time experiment testing the response of rivers to land use changes. The Papakating watershed has more agricultural land use and the Wallkill watershed has more urban and forested land, comparatively. Field and GIS analyses were conducted to measure the differences in channel characteristics between the Wallkill and Papakating rivers. Channel widths changes were measured from aerial photos taken in 1930 and 2007. Current watershed land uses were determined using 2007 data. Rapid Geomorphic Assessments (RGA) were taken at 13 different sites along the Papakating and Wallkill rivers. Along the Wallkill, sites with larger drainage areas have experienced a greater change in channel width over the past 77 years, most likely as a result of urbanization. Stream health, based on Rapid Geomorphic Assessment Scores, decreased as the percentage of urban land use and impervious surface increased. We show that stream health is impacted by the percentage of impervious surface and urbanized land. The health of the Papakating deteriorated as the amount of urban land use and impervious surfaces increased. Sites with larger amounts of forested land upstream were healthier as measured by their RGAs. This study highlights streams that have been impacted by differing land uses, identifying sites for further research and potential remediation.