Influence of Applying Infiltration and Retention Objects to the Rainwater Runoff on a Plot and Catchment Scale – Case Study of Służewiecki Stream Subcatchment in Warsaw

Abstract

This article presents the results of an analysis aimed at determining the influence of applying selected types of objects for the infiltration and retention of rainwater (LID – low impact development objects), on a plot scale (area of a shopping mall) and in the subcatchment of Sluzewiecki Stream in Warsaw, on the characteristics of surface runoff/outflow as well as retention and infiltration depths, in response to a single rainfall event. The following types of objects were accounted for in the study: permeable soil layer, green roof, permeable paved parking lot surface, and infiltration trench. The SWMM model (storm water management model), designed by the U.S. Environmental Protection Agency was used to carry out simulation calculations for the individual scenarios of applying infiltration and retention objects on a plot and catchment scale. The effect of applying LID objects throughout the analyzed area was, in both cases, a reduction in the depth of surface runoff, outflow volume and, at the same time, an increase in the infiltration and retention depths. The most significant reduction in surface runoff on the plot scale (approximately 99%) occurred in the case of calculation scenarios calling for the application of infiltration trenches (scenario LID3), as well as permeable layers of soil and gravel (LID5 and LID6). The most significant reduction in runoff/outflow on the catchment scale was achieved by the combined application of objects of “permeable soil layer” and so-called “green roofs” (LID5). The reduction in the runoff depth and peak flow rate amounted to 50.0 and 38.5%, respectively, as compared to runoff from the catchment at the current state of its urbanization. The influence of urbanization that the plot of land and subcatchment area had undergone between 1970 and 2005 also was analyzed. The increased urbanization of the catchment, determined as 40%, resulted in an increase in the maximum flow rate in the “Rosola” profile (approximately 19 times higher), as well as outflow volume (approximately 39 time higher).