Urban watershed management: The role of vegetation

Runoff from urban watersheds is of major concern due to the flood hazard caused by the replacement of natural vegetative cover with impervious surfaces and as a contributor to nonpoint source pollution. Natural resources are not currently considered to be essential components of urban infrastructure and although forest cover has been demonstrated to be a significant factor in controlling runoff, substantive biotic controls in the form of best management practices do not exist for urban watershed protection and remeadiation. This study explores the role of vegetation from both a landscape and an ecosystem perspective as a potentially cost effective contributor to stormwater management.; Through use of GIS and the Hydrologic Simulation Program-FORTRAN, HSPF, the effects of alternative vegetation patterns on runoff from different land uses and soil/land cover types was established for the upper Gwynns Falls watershed in Baltimore, Maryland. Study results indicate that conservation of existing forest cover and replacement of trees on pervious sites, particularly in intensive use areas can significantly reduce total runoff, high 10 percent flows and average peak flows; and can increase low flow. Furthermore, it was determined that tree canopy cover over impervious surfaces has limited effect on runoff.