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UBC Theses and Dissertations

Rainfall interception in an urban environment Asadian, Yeganeh


Vegetation interception loss plays an important role in controlling the water balance of a watershed, especially where urban development has taken place. The aim of this study is to document the importance of urban trees as a form of ‘green infrastructure’ to reduce stormwater runoff and rainwater intensity, and cause a delay in precipitation reaching the ground. A 21 months study was carried out in the North/West Vancouver in British Columbia to determine how effective urban trees are to intercept and detain rainwater. We applied a unique methodology for measuring rain/throughfall under 54 different urban trees using a system of PVC pipes hung beneath the canopy to capture the throughfall where it drained into a rain gauge attached to a data logger. To ensure that the study adequately captured the range of throughfall variability, trees were selected to sample different landscape sites (streets, parks, and natural forested areas), elevations, tree type, health condition and species, including Douglas-fir (Pseudotsuga menziesii), Western red cedar (Thuja plicata), Bigleaf maple (Acer macrophyllum), Oak (Quercus sp.), Copper beech (Fagus sylvatica), Horse chestnut (Aesculus hippocastanum), Cherry (Prunus sp.), and Poplar (Populus sp.). Interception loss and throughfall were monitored from February 2007 until November 2008. Rainfall interception varied seasonally for all species. Interception losses accounted for on average 76.5% and 56.4% of gross precipitation for coniferous and deciduous trees, respectively. The interception loss varied depending on canopy structure, climatic conditions, and rainfall characteristics. The results showed that urban trees intercept and evapotranspire more rain than trees in forested environments. Together with the delay in runoff trees can act as an effective stormwater management tool on individual properties.

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