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 Służewiecki 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 “Rosoła” profile (approximately 19 times higher), as well as outflow volume (approximately 39 time higher).

The disadvantage of radar measurements is that the obtained rainfall data is imprecise. Therefore, the use of radar data in hydrological applications usually requires correction. The main aim of the study was to verify and optimize various methods of estimating the rainfall depths for single events based on radar data, as well as determining their influence on the values of peak flow and outflow volume of hydrographs simulated using the SWMM (Storm Water Management Model) hydrodynamic model. Regression analyses were used to find a relationship between the rain gauge rainfall rate R and radar reflectivity Z for the urban catchment of the Służewiecki Stream in Warsaw, Poland. Five methods for determining calculational values of radar reflectivity in reference to specific rainfall cells with 1 km resolution within an event duration were applied. Moreover, the correction coefficient for data from the SRI (Surface Rainfall Intensity) product was established. The Z-R relationships determined in this study offer much better rainfall rate estimation as compared to Marshall-Palmer’s relationship. Different scenarios were applied to investigate the stream response to changes in rainfall depths estimated on the basis of radar data, in which the data both for 2 existing, as well as 64 virtual, rain gauges assigned to appropriate rainfall cells in the catchment were included. Relatively good agreement was achieved between the measured parameters of the hydrograph of flows and those simulated in response to rainfall depths which had been calculated for single events using the correction coefficient and the determined Z-R relationships. Radar estimates of rainfall depths based on the tested methods can be used as input data to the SWMM model for the purpose of simulating flows in the investigated urban catchment.

In the majority of small urban catchments, there is a problem with obtaining precipitation data necessary for hydrological applications and analyses in the scope of assessing flood risk. One of the means of measuring rainfall depth is to make use of weather radar technology, which provides information on the spatial and temporal distribution of rainfall in a catchment. In the work, the dependency between radar reflectivity (Z) and rainfall rate (R) was determined on the basis of a few events measured at two precipitation stations located in the Służewiecki Stream catchment in Warsaw, Poland. Making use of the Z-R relationship as well as values of radar reflectivity, the amount of rainfall for the analysed event was calculated and compared with the amounts of rainfall measured using rain gauges. Relatively good compatibility between the rainfall totals was obtained for the majority of events. Rainfall depths obtained for two selected events on the basis of data from the weather radar were applied to simulate flows in the analysed catchment using the SWMM (Storm Water Management Model) hydrodynamic model. Values of the relative error calculated on the basis of measured flows and flows calculated in reaction to rainfalls estimated using the Z-R relationship were, in the majority of cases, lower than 25%. Simulations carried out on the SWMM model for a few rainfall scenarios in response to rainfall depth measured at precipitation stations and estimated on the basis of radar data revealed the possibility of the occurrence of flooding in the catchment as a result of the overflow of rainfall collectors.

The procedure of the rainfall–runoff (R-R) model, based on the instantaneous unit hydrograph (IUH) method and used to calculate the probable flows in 8 profiles of the Losse river (on the stretch from 5+476 to 7+596 km) for three flood scenarios (Qextreme, Q1% and Q10%), has been presented in this work. A computer program developed by the author was used to conduct the analyses, enabling the flows to be simultaneously calculated for each of the analyzed profiles in response to 10 rainfall events of varying duration and a given exceedance probability. The obtained values of probable flows were recalculated into corresponding water table levels using the WSP-ASS program (Water Level Program). The extent of the flooding and water depths for three flood scenarios were calculated based on the levels of the water table and terrain elevation data ("Digital Terrain Model"). As a final effect of the analyses, flood hazard maps for the analyzed stretch of the Losse River were constructed, enabling the consequences of flooding to business activities, the infrastructure, the environment, and human health and life to be assessed.

The main aim of the research presented in the work was to assess the usefulness of the dynamic SWMM (stormwater management model) and the conceptual SBUH (Santa Barbara Urban Hydrograph) model for simulating and predicting flow hydrographs in a small urbanized catchment under conditions of controlled (using valves) outflow from stormwater retention tanks in response to rainfall events. Most of the analyzed catchment of the Służewiecki Stream consists of the area beneath F. Chopin International Airport in Warsaw. A further aim of the study was the development of method for indicating the concentration time for a given rainfall–runoff event, where the influence of delaying the outflow of stormwater from the catchment as a result of its retention in tanks on the value of this parameter will be accounted for. The values of the median of absolute errors, obtained in a simulation using the SWMM in relation to peak flows and hydrograph volumes for the analyzed events, were 15.4 and 18.4%, respectively. The adequate values of simulation errors, obtained in the SBUH model using concentration times determined according to the developed method, were 11.4 and 15.4%. Satisfactory results of simulations were received using both models.

In this study, regression analyses were used to find a relationship between the rain gauge rainfall rate R and radar reflectivity Z for the urban catchment of the Służewiecki Stream in Warsaw, Poland. Rainfall totals for 18 events which were measured at two rainfall stations were used for these analyses. Various methods for determining calculational values of radar reflectivity in reference to specific rainfall cells with 1-km resolution within an event duration were applied. The influence of each of these methods on the Z-R relationship was analyzed. The correction coefficient for data from the SRI (Surface Rainfall Intensity) product was established, in which the values of rainfall rate are calculated based on parameters a and b determined by Marshall and Palmer. Relatively good agreement between measured and estimated rainfall totals for the analyzed events was obtained using the Z-R relationships as well as the correction coefficient determined in this study. Rainfall depths estimated from radar data for two selected events were used to simulate flow hydrographs in the catchment using the SWMM (Storm Water Management Model) hydrodynamic model. Different scenarios were applied to investigate the stream response to changes in rainfall depths, in which the data both for 2 existing as well as 64 virtual rain gauges assigned to appropriate rainfall cells in the catchment were included.