" BES Project Abstracts 2005
Institute of Ecosystem Studies

2005 BES Annual Meeting Presentation and Poster Abstracts

Modeling tree effects on runoff generation in an urban catchment
Jun Wang, Theodore Endreny, David Nowak
Abstract: A semi-distributed, physical based urban forest effects hydrological model (UFORE-Hydro) was created to simulate and study tree effects on urban runoff. The interception model modifies an existing physically-based routine to account for variable density urban trees and short vegetation. Phenology routines are used to seasonally adjust leaf area index and determine maximum stem and leaf interception storage. Variable source area and Green- Ampt theories are used to simulate runoff generation from pervious areas. Different methods are designed to simulate evaporation from tree canopy and from short vegetation. UFORE-Hydro was applied in Dead Run catchment, Baltimore, Maryland, USA for the year 2000. Simulated annual interception loss by the tree canopy was about 23%. Storm specific tree interception rates exceeded 48% for small storms during the period. Dead Run's connected impervious area was estimated 19%, and contributed about 50% of total simulated annual runoff. Predicted runoff rates and volumes demonstrate algorithm functionality and illustrate the significant role of trees in reducing runoff, especially for small storms during leaf-on conditions. Atmospheric and vegetation factors influence interception through vegetation type and leaf area, evaporation rates, and precipitation intensity and duration. Urban hydraulic connected impervious surface, in the absence of trees, is the dominant control on urban runoff generation. UFORE- Hydro is developed to study urban tree effects on hydrological processes simulation and provides a research and management tool for urban foresters.