In many instances urban streams are flowing along streets, parks, and all throughout cities yet they remain invisible to people due to urban infrastructure and stream channel modifications. To understand current stream conditions and associated riparian areas within an urban watershed, Forest Service scientists generated a stream network using historic and current hydrological data from federal and state agencies, along with geo-referenced field data to describe stream structural and physical characteristics. The characterization of a tropical, urban stream network is taking place in the Río Piedras, a major river and a component of the San Juan Bay Estuary in the capital of Puerto Rico. Most of stream reaches are currently modified into pluvial drainages and concrete walled channels. Only 19 percent of the stream segments were classified as unmodified, with substrate that can be considered natural and connected to riparian areas. The next phase of this project will further quantify historical changes to the stream network, the influence of superficial pluvial drainages and riparian cover in light of urban green infrastructure needs, potential restoration of stream reaches, and riparian area functions.