Water dynamics at the urban soil-atmosphere interface—rainwater storage in paved surfaces and its dependence on rain event characteristics

Abstract

Abstract Purpose The surface store governs the rainwater partition, e.g., water storage and evaporation on paved surfaces, especially for low-intensity and low-sum rain events, which account for the greatest part of the total rainfall in a temperate climate city like Berlin, Germany. The surface store S is a fixed value, dependent on surface relief and pore system characteristics. Contrary, in this study, the surface storage was assumed to depend also on the rain intensity, thus being variable from event to event. Materials and methods The surface store filling dynamics for dense (DP), porous (PP), and highly infiltrative (IP) paving materials were studied in a rainfall simulator. Irrigation intensities p ranged from 0.016 to 0.1 mm min−1 which represent the 25 to 88% quantiles of the rain event distribution in Berlin, Germany (1961 to 1990). Results and discussion Three surface stores can be separated: storage until initial runoff, Sf, at maximum filling, Sm, and for steady-state runoff, Seq—all of them can be regarded as effective stores depending on the aim of its use. The equilibrium store varies from 0.2 to 3 mm for DP, PP, and IP for the investigated rainfall intensities. Conclusions For all pavers, the surface store depends on rainfall intensity, which was shown experimentally and confirmed by numerical simulation of the infiltration. We introduce a simple and robust method to describe Sf, Sm = f(p) for different pavers. Pavers can evaporate a multiple of their surface store per day, depending on the rainfall distribution, which implicates the need for high temporal resolutions in urban hydrology modeling. Pavers can evaporate a multiple of their surface store per day, depending on the rainfall distribution. That implicates the need for high temporal resolutions in urban hydrology modeling.