Design rainfalls are essential parameters in designing and assessing combined and stormwater sewers and are still used today. They create idealized intensity profiles with statistically determined parameters. Their gradual development is based on the development of computer technology, measuring instruments, and measurement campaigns’ progress. However, climate change is causing changes in precipitation events’ characteristics, so it is important to focus on reassessing them and adapting to current conditions. The paper summarizes the knowledge about the development of design rains to reveal their potential for the future.

As a result of changes in social, economic, and political relations, undesirable phenomena are created that have an adverse effect on the urban environment. Surface runoff represents one of several risks to environmental policy, causing the major problem in urban agglomerations. In an urbanized area, it causes an increased runoff volume and the flood peak. Also, it affects increasing the contamination of urban rainwater. The significant problem of surface runoff formation in urban river basins is the accumulation of pollutants on the surface of paved areas during the rainless period. In the case of the formation of surface runoff, these substances come into movement. It is assumed that the most polluted rainwater is in the initial phase of runoff formation. However, not all authors agree with the statement. In some literature, this phenomenon is termed the first flush. Given the above facts, the study focuses on surface runoff characteristics in terms of its quality and quantity in the initial phase of surface runoff formatting. The study aims to summarize and compare the results of several studies to evaluate the first rainwater flush in an urbanized area.

The purpose of mathematical modelling of sewer networks is mainly to assess the hydraulic capacity and monitor its behaviour under different conditions to predict the future state. Sewerage network models are also part of the design process. Their advantage is the possibility of simulating the future state of the network and the precipitation and runoff process in the context of climate change. With the help of simulations, it is possible to anticipate future conditions in urban catchments and thus effectively design new networks. The aim of this paper is to summarize mathematical simulation models that are used to model sewer networks.

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The inhabitants produce the sump waters and accumulate temporarily in the sumps. This is sewage that must be treated before it is discharged to surface waters. Slovak legislation does not allow the discharge of such waters into the soil. The possibilities of sump water treatment are given by the water management equipment of the given locality where sewage water is produced. The most common treatment method is transported at municipal wastewater treatment plants, which are, however, largely congested. In many cases, the sump water is no longer able to receive in WWTP. Another way is domestic wastewater treatment plants, and also they are wastewater treatment plants exclusively for sump waters. Sump waters have a predominantly high organic content and therefore their quality needs to be constantly monitored. The most important monitored characteristics of sump waters are COD (Chemical Oxygen Demand) and BOD5 (Biological Oxygen Demand). The high concentration of these substances in the sump water can adversely affect the processes at the municipal wastewater treatment plant. Due to the rapid development of rural settlements without a functioning sewerage system, it is necessary to intensify or adapt the existing wastewater treatment plants. However, many engineers see the solution to this problem in the construction of separate wastewater treatment plants for sump waters.