Quantifying rainfall interception by urban low-height shrub canopy: can the uncertainty in stormwater management credit for trees and shrubs be minimized?

Precipitation interception by vegetation canopies is a major component of the hydrologic cycle. Urban trees and shrubs provide a valuable ecosystem service by reducing the volume of rainfall that reaches the ground. Multiple municipalities have established programs of stormwater credit for trees. However the limited number of urban interception studies contributes to large uncertainty associated with such programs.Our field experiment involved small forms of four shrub species. The obtained data showed significant differences in interception properties among all four species. Throughfall and precipitation intensities expressed very strong linear relationship for the entire range of observed rainfall intensities. The observations suggest that reduction of throughfall intensity by the canopy during a rainstorm determines the bulk of interception depth.We discuss that continuous observations of interception by tree and shrub species commonly used in urban greening programs will help to minimize uncertainty granting stormwater credits for trees and shrubs.