Rainfall interception of urban trees: event characteristics and tree
morphological traits
Abstract
The rapid expansion of impermeable surfaces in cities has a major impact
on urban hydrology. Infiltration of rainwater is reduced and water runs
off faster with higher runoff peaks. Urban trees as stormwater
management tools are becoming more relevant to reduce flood risks in
addition to other ecosystem services. An in-situ field experiment to
measure throughfall on Norway maple ( Acer platanoides)
and small-leaved lime ( Tilia cordata) was conducted to
determine the interception of solitary urban trees with different
degrees of surface sealing in the city of Freiburg, Germany. The
relationships between rainfall characteristics, tree morphological
traits, and the interception behavior were investigated with eight trees
per species. 76 recorded rainfall events were evaluated from April to
September 2021. Average interception values were higher for small-leaved
lime (70.3 ± 6.6%) than for Norway maple (54.8 ± 10.3%) and hence much
higher than in a typical forested environment. The average interception
loss of all recorded events was 2.58 ± 0.60 mm for Norway maple and 3.73
± 0.29 mm for small-leaved lime. For both tree species, significant
linear correlations were found between the relative interception and
other factors like rainfall depths, the leaf area index (LAI), and the
plant area index (PAI) (adj.R 2 > 0.45).
In contrast to Norway maple, small-leaved lime also showed significant
relationships of several tree morphological parameters with the
interception (adj.R 2 > 0.43). LAI, which
also effects the interception, of both tree species significantly
decreased with the degree of surface sealing. Our results provide a
better understanding of the interception process of solitary trees for
different urban sites and allows to parameterize interception based on
measurable properties. However, further field experiments with various
tree species need to be conducted to obtain a larger database for
typical parameters in models and to support urban planners in managing
stormwater runoff.