Increasing urbanization and the associated sealing of areas and the use of storm sewer systems for drainage not only increase the risk of flooding but also reduce water quality in streams into which stormwater is discharged. Green infrastructure (GI) measures are applied with the aim of managing this stormwater sustainably and reducing the associated risks. To this end, a quantitative–qualitative approach was developed to simulate GI—namely, rain gardens, bioretention cells, and vegetative bioswales—at the urban catchment scale. The findings highlight the potential of applying GI measures to managing stormwater more effectively in urban environments and mitigating its negative pollution-related impacts. For the housing estate analyzed, a simulated implementation of GI resulted in a reduction in pollution, measured as total nitrogen (N; 9–52%), nitrate-N (5–30%), total phosphorus (11–59%), chemical oxygen demand (8–46%), total suspended solids (13–73%), copper (12–64%), zinc (Zn; 16–87%), polycyclic aromatic hydrocarbons (16–91%), and the hydrocarbon oil index (HOI; 15–85%). Reducing the concentrations of pollutants minimizes the risk to human health determined via the HOI from a low-risk level to zero risk and reduces the ecological risk in terms of Zn pollution from a significant risk to a low risk of adverse effects. The modeling conducted clearly shows that the GI solutions implemented facilitated a quantitative reduction and a qualitative improvement in stormwater, which is crucial from an environmental perspective and ensures a sustainable approach to stormwater management. Lowering the levels of stormwater pollution through the implementation of GI will consequently lower the environmental burden of pollutants in urban areas.

Urbanization leads to the growth of impervious surfaces, which increases surface runoff, causing pluvial and flash flood phenomena. Furthermore, it significantly limits the infiltration of stormwater into the ground; this, in turn, reduces groundwater supply, ultimately intensifying drought effects. In order to adapt urbanized areas to climate change, the objective is to stop these unfavorable processes and strive for recreating the natural water cycle through developing decentralized stormwater management practices on private properties. An important management instrument that motivates property owners to invest is economic incentives, such as stormwater or impact fees associated with a system of rebates/discounts that depend on the applied stormwater runoff reduction solutions. Herein, we analyze a new economic instrument—a fee for reducing natural field retention—which is planned to be introduced in Poland. We assessed the incentive and funding (income-generating) function of the fee based on the example of the Sudół river catchment in Krakow, Poland. The research involved conducting simulation calculations and assessing the incentive impact through calculating investment Net Present Value (NPV), which is the investor’s response to the proposed economic incentives included in the structure of the fee and the rebate system. This study demonstrated errors and loopholes in the suggested fee rules—too low rates that prevent achieving profitability (negative NPV) for small-scale stormwater retention practices, and incorrect conditions that enable obtaining discounted fees. We also estimated the fee rate that ensures investment profitability.

Changes in the land use of urban catchments and the discharge of stormwater to rivers are causing surface water pollution. Measurements were taken of the quality of discharged stormwater from two areas with different types of development: a residential area and a residential–commercial area, as well as the quality of the Sudół River water below the sewer outlets. The following indicators were studied: TSS, COD, N–NO₃, N–NO₂, TKN, TN, TP, Zn, Cu, Hg, HOI, and PAHs. The influence of land use on the magnitudes of flows in the river was modeled using the SCS–CN method and the Snyder Unit Hydrograph Model. The results showed an increase in sealing and a resulting increase in surface runoff. Concentrations of pollutants in stormwater and analysis of the potential amounts of loadings contributed by the analyzed stormwater outlets indicate that they may be responsible for the failure to meet environmental targets in the Sudół River. Environmental risk assessment shows that the aquatic ecosystem is at risk. A risk factor indicating a high risk of adverse environmental effects was determined for N–NO₃, Zn, and Cu, among others.

The complex integration of water and flood risk management, climate change adaptation, and sustainable planning requires advanced, dynamic tools that are unavailable to most planning offices. This paper aims to demonstrate that the available GIS technologies and large, variable, and diverse datasets (big data) already allow us to create effective, easy-to-use, and, most importantly, cross-sectorial and holistic tools that integrate issues related to planning, flood risk management, and adaptation to climate change. Resulting from an interdisciplinary study of districts in Kraków, Poland, which have been heavily affected by pluvial floods in recent years, the accumulated runoff mapping analysis method proposed in this paper can be considered an effective planning tool that can be used at the initial stage of pluvial flood risk assessment and, above all, for spatial planning analysis and urban design. The proposed tool accounts for a correlation of development, land cover, and hydrological conditions, as well as their impact on vulnerability and the urban climate, while integrating environmental, urban, and social amenities. Intended for preliminary planning phases, it uses open-source software and data, which, although giving approximate runoff volumes, do not require advanced hydrological calculations or costly and time-consuming field research. The method allows studying alternative scenarios that can support the cross-sectorial, inclusive, and interdisciplinary discussion on new developments, sustainable planning, and adaptation to climate change. Most importantly, it can reduce, if not eliminate, issuing decisions that may have negative impacts on urban areas and enhance their resilience before more sophisticated, detailed, and advanced methods are ready for implementation.

Currently, effective rainwater management in urban areas requires a modern and comprehensive approach, with mathematical modelling methods at its foundation. The aim of this study was to estimate the impact of the use of dispersed green infrastructure (GI) – specifically, drainage-equipped rain gardens (bio-retention cells, or BC) – and their operational hydrological performance on the scale of an urban catchment, particularly in reducing the amount of rainwater discharged directly to the receiver. An additional objective was to determine the relationship between the total rainwater inflow per unit area and the capacity percentage reduction in individual BC facilities. In this research, a hydrodynamic single-event precipitation model was built and calibrated for an existing housing estate in Cracow (Poland) using the Storm Water Management Model (SWMM). The functioning of the GI is represented by Low Impact Development (LID), which was simulated for a number of precipitation scenarios (S ₀ –S ₇ ) with durations of 4.2, 15, 30, 45, 60, 90, 120 and 180 minutes, and a probability of occurrence of p = 10% (indicating a 10% chance of occurrence in any given year). The results demonstrated significant potential for reducing the peak flow of rainwater by an average of 94%, and reducing the total volume of rainwater by an average of 86%, for all simulated precipitation at the outfall of the entire system. Analysis of individual BC facilities revealed reductions in rainwater ranging from 67% to 95% of capacity for GI facilities, depending on the duration of the rainfall. Notably, more significant reductions in GI facilities were observed in cases of short, intense rainfall. The analysis of the individual BC facilities with the highest efficiency showed that the maximum values of total inflow per 1 m ² of their surface area, reduced to 100% for rainwater inflow, occurred during heavy rainfall of 15 min (S ₁ ) and amounted to 29.72 L/m ² (average 5.79 L/m ² ).

This study provides a quantitative assessment of the combined effects of progressive urbanization and changes in precipitation patterns (PPs) on the urban water cycle. The primary objective was to evaluate historical (1940–2024) and projected (to 2060) changes in total annual surface runoff (TSR) and retention capacity (RC) in the highly urbanized catchment of the Dłubnia River in Cracow, Poland. Simulations were performed using the EPA SWMM hydrodynamic model, supported by digitized historical land-use maps and long-term meteorological records. The results demonstrate that the dominant driver of the observed 6.4-fold increase in TSR and 6.8-fold loss of retention capacity (LRC) over the study period was the progressive increase in impervious surfaces. Although inter-annual variability in the amount and structure of annual precipitation (AP) strongly correlates with annual TSR (r = 0.97), its contribution to the long-term upward trend in TSR is marginal (r = 0.19). Land use and land cover change (LULC) exhibits an extremely strong correlation with the long-term TSR trend (r = 0.998). The study also highlights the high effectiveness of nature-based solutions (NbSs), particularly bioretention cells (BCs)/rain gardens, in mitigating the adverse hydrological effects of excessive surface sealing. Implementation of BCs covering just 3–4% of the total drained roof and road area is sufficient to fully offset the projected combined negative impacts of further urbanization and climate change (CC) in scope Representative Concentration Pathways (RCP4.5 and RCP8.5) projections on catchment retention capacity by 2060. These findings position strategically targeted, relatively small-scale bioretention as one of the most effective and feasible urban adaptation measures in mature, densely developed cities.