Skip to main content

Rainfall interception by Santa Monica's municipal urban forest


Effects of urban forests on rainfall interception and runoff reduction have been conceptualized, but not well quantified. In this study rainfall interception by street and park trees in Santa Monica, California is simulated. A mass and energy balance rainfall interception model is used to simulate rainfall interception processes (e.g., gross precipitation, free throughfall, canopy drip, stemflow, and evaporation). Annual rainfall interception by the 29,299 street and park trees was 193,168 m3 (6.6 m3/tree), or 1.6% of total precipitation. The annual value of avoided stormwater treatment and flood control costs associated with reduced runoff was $110,890 ($3.60/tree). Interception rate varied with tree species and sizes. Rainfall interception ranged from 15.3% (0.8 m3/tree) for a small Jacaranda mimosifolia (3.5 cm diameter at breast height) to 66.5% (20.8 m3/tree) for a mature Tristania conferta (38.1 cm). In a 25-year storm, interception by all street and park trees was 12,139.5 m3 (0.4%), each tree yielding $0.60 (0.4 m3/tree) in avoided flood control costs. Rainfall interception varied seasonally, averaging 14.8% during a 21.7 mm winter storm and 79.5% during a 20.3 mm summer storm for a large, deciduous Platanus acerifolia tree. Effects of differences in temporal precipitation patterns, tree population traits, and pruning practices on interception in Santa Monica, Modesto, and Sacramento, California are described.

This is a preview of subscription content, access via your institution.


  • American Forests (1996) Urban ecological analysis report, Phase 1: Economic benefits and costs of the urban forest in low income and non-low income communities. Final report NA-94-0297. American Forests. Washington, D.C.

    Google Scholar 

  • Condon, P. and Moriarty, S. (1999) Second Nature: Adapting LA's Landscape for Sustainable living. TreePeople, Los Angeles.

    Google Scholar 

  • Department of Public Works of Los Angeles County (1991) Hydrology-Sedimentation Manual.

  • Hung, M.C. and Ridd, M.K. (2002) A subpixel classifier for urban land-cover mapping based on a maximum-likelihood approach and expert system rules. Photogrammetric Engineering and Remote Sensing 68, 1173–1180.

    Google Scholar 

  • McPherson, E.G. and Simpson, J.R. (2002) A comparison of municipal forest benefits and costs in Modesto and Santa Monica, California, USA. Urban Forestry and Urban Greening, 1, 61–74.

    Google Scholar 

  • McPherson, E.G., Simpson, J.R., Peper, P.J. and Xiao, Q.F. (1999) Benefit-cost analysis of Modesto's municipal urban forest. Journal of Arboriculture, 25, 235–248.

    Google Scholar 

  • McPherson, E.G., Simpson, J.R., Peper, P.J., Scott, K.I. and Xiao, Q. F. (2000) Tree Guidelines for Coastal Southern California Communities. Local Government Commission, Sacramento, CA.

    Google Scholar 

  • McPherson, E.G. (1984) Energy-Conserving Site Design, Washington, D.C.: American Society of Landscape Architects.

    Google Scholar 

  • Peper, P.J., McPherson, E.G. and Mori, S.M. (2001a) Predictive equations for dimensions and leaf area of coastal Southern California street trees. Journal of Arboriculture 27, 169–180.

    Google Scholar 

  • Peper, P.J., McPherson, E.G. and Mori, S.M. (2001b) Equations for predicting diameter, height, crown width, and leaf area of San Joaquin Valley street trees. Journal of Arboriculture 27, 306–317.

    Google Scholar 

  • Peper, P.J. and McPherson, E.G. (2003) Evaluation of four methods for estimating leaf area of isolated trees. Urban Forestry and Urban Greening 2, 19–30.

    Google Scholar 

  • Sanders, R.A. (1986) Urban vegetation impacts on the hydrology of Dayton, Ohio. Urban Ecology 9, 361–376.

    Google Scholar 

  • Xiao, Q.F., McPherson, E.G., Ustin, S.L., Grismer, M.E. and Simpson, J.R. (2000a) Winter rainfall interception by two mature open-grown trees in Davis, California. Hydrological Processes 14, 763–784.

    Google Scholar 

  • Xiao, Q.F., McPherson, E.G., Ustin, S.L. and Grismer, M.E. (2000b) A new approach to modeling tree rainfall interception. Journal Geophysical Research (Atmospheres) 105, 29173–29188.

    Google Scholar 

  • Xiao, Q.F., McPherson, E.G., Simpson, J.R. and Ustin, S.L. (1998) Rainfall interception by Sacramento's urban forest. Journal of Arboriculture 24, 235–244.

    Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

Xiao, Q., McPherson, E.G. Rainfall interception by Santa Monica's municipal urban forest. Urban Ecosystems 6, 291–302 (2002).

Download citation

  • Issue Date:

  • DOI:

  • urban forest
  • rainfall interception
  • evaporation
  • urban runoff reduction