A watershed is a portion of land that drains into a specific body of water. Different watersheds are separated by high topographic points such as hills or mountains. Watersheds can be viewed from a broad perspective – all water in Philadelphia and its adjacent suburbs eventually drains to the Delaware River – or from a more site-specific angle – most of Rolling Hill Park drains directly to Mill Creek while a smaller section drains to the unnamed Mill Creek tributary along Rose Glen Road.

Below is a story map, created by our student partners Gina Talamo and Julie Greenwald of Villanova University’s Department of Geography and the Environment, examining the watersheds and streams in Lower Merion and Narberth. Zoom in to discover smaller watersheds within the larger ones and track the path stormwater takes.

The streams on the map are from the U.S. Geological Survey’s National Hydrography Dataset and the watersheds were delineated using LiDAR data. Unnamed streams on the map do not have official names. Some streams were too small to register on the Dataset.