Field evaluation of precipitation interception potential of green façades

This paper evaluates the potential of living green façades in intercepting precipitation and delaying ‘canopy through-flow’ (i.e. total precipitation minus canopy interception). Precipitation interception and delayed through-flow (i.e. discharge) from two visually distinct mixed-species green façade configurations – one, fully-foliated and the other twiggy (respectively as proxies for well-managed and degenerated stands) – were monitored using rain gauges located at their base. The precipitation interception levels for the fully-foliated and the twiggy stands respectively ranged between 54 and 94% and 10–55% of the total precipitation. Regression of the experimental data showed interception volumes were proportional to the ambient precipitation up to a maximum tested event size of 35 mm. The fully-foliated façade gave a delay of at least 30 min from the start of precipitation events to the first measured through-flow, compared to about 15 min for the twiggy façade. This highlights the potential for well-foliated and maintained façades to contribute to reducing peak flows within urban drainage infrastructure, and the importance of façade maintenance in ensuring good interception and delay properties.