ASCE-EWRI, World Water & Environmental Congress, In Symposia Proceedings, Protection & Restoration of Urban & Rural Streams, Philadelphia, PA, June 2003 1 Ecological Benefits of Riparian Reforestation in Urban Watersheds W.C. Hession 1 , T.E. Johnson 2 , D.F. Charles 2 , R.J. Horwitz 2 , D.A. Kreeger 2 , D.J. Velinsky 2 , J.E. Pizzuto 3 , B.D. Marshall 4 , and J.D. Newbold 5 . 1 Department of Civil and Environmental Engineering, University of Vermont, Burlington, VT 05405; PH (802) 656-1953; FAX (802) 656-8446; email: hession@emba.uvm.edu 2 Patrick Center for Environmental Research, The Academy of Natural Sciences, Philadelphia, PA 19103; PH (215) 299-1118; FAX (215) 299-1079; email (in order above): tjohnson@acnatsci.org , charles@acnatsci.org , horwitz@acnatsci.org , kreeger@acnatsci.org , velinsky@acnatsci.org 3 Department of Geology, University of Delaware, Newark, DE 19716; PH (302) 831- 2710; FAX (302) 831-4158; email: pizzuto@udel.edu 4 Department of Ecology, Montana State University, Bozeman, MT 59717; PH (406) 994-4068; FAX (406) 994-3190; email: brettm@montana.edu 5 Stroud Water Research Laboratory, Avondale, PA 19311; PH (610) 268-0490; FAX (610) 268-0490; email: newbold@stroudcenter.org Abstract Riparian forest restoration has become a major focus of watershed initiatives to improve degraded stream ecosystems. In urban watersheds, however, the ability of riparian forests to improve stream ecosystems may be diminished due to widespread, upland disturbance. We studied 12 paired forested and non-forested stream reaches located on 1 st through 3 rd order streams in the Piedmont region of southeastern Pennsylvania and northern Delaware to examine the combined influence of watershed urbanization and riparian vegetation on stream health. The paired reaches are nearly contiguous, so all significant variables except riparian vegetation are held constant. The extent of urban development of the watersheds upstream of the paired reaches varies considerably, allowing us to determine the combined influence of riparian vegetation and urbanization on stream health. Stream health was assessed using multiple structural and functional stream ecosystem attributes, including: channel morphology and physical habitat, water chemistry, nutrient cycling, benthic algae, benthic macroinvertebrates, fishes, and food web linkages. Analyses of channel morphology data indicate that (1) channels with forested riparian zones are wider than channels with non-forested riparian zones, (2) channels in urbanized watersheds are wider than channels in non-urbanized watersheds, and (3) the effect of riparian vegetation is independent of the level of urbanization. In general, the biological data indicate that forested stream reaches exhibit more diversity, while the non-forested reaches tend to have higher biomass. The combined influence of urbanization and riparian condition on stream health is complicated and shows varied response depending on the biological attribute measured.