Unresourceful usage of rainwater continues to be a serious problem as this type of natural resource is still treated as wastewater that most often ends up directly in the sewer system. The aim of the article is to present a concept of sustainable rainwater management within a completed housing estate in Cracow (Poland). Sustainable solutions are proposed, such as rain gardens, soakaways, permeable surfaces, and infiltration boxes, limiting the surface runoff, feasible for implementation in an existing development. Their efficacy was shown by estimating the runoff reduction and two financial assessments: (1) the required investment costs converted to costs per 1 m² of residential area and as per 1 household, and (2) the assessment of financial profitability by the rate of return and the payback period, which are the basic tool for making decisions by potential investors: developers and residents. On the cost side, investment costs are included, and on the benefit side, savings resulting from the reduction of national and municipal rainwater fees. The analysis also aims to examine the incentive nature of these fees. National rainwater drainage fees, which have been introduced to encourage rainwater retention, have low non-incentive rates and the potential benefits of reducing them maybe around 1% of investment capital, which gives a payback period of almost 100 years. Higher rates of municipal fees are more motivating for investors; the proposed concept of rainwater management can potentially bring savings of around 9% (rate of return), and investment can be recovered within 12 years.

The protection of larger built-up areas that constitute sections of actively functioning urban zones is a challenge, even under favourable political and economic conditions. The case of Krakow’s historical town centre, which is protected as a historical site by national law and it was placed on the UNESCO World Heritage Sites List in 1978, clearly demonstrates how difficult it is to reconcile the passive character of current conservation doctrines with the demands of the free market and growth-oriented economy, when developer pressure is not sufficiently balanced out by public opinion and urban activist movements, when planning tools are incomplete or insufficient, and the criteria according to which strategic decisions are made are of a quantitative rather than a qualitative character. Apart from commonly encountered problems that are associated with the gentrification of town centres or the negative impact of mass tourism, Krakow must also face a growing flood hazard that stems from its specific and unfavourable hydrological and hydrogeological conditions that are compounded by the uncontrolled and uncoordinated expansion of urbanised areas, the decay of the natural environment, and the consequences of climate change. This article presents the multi-aspect site-specific conditions of the historical centre of Krakow, as well as the analysis of its protection as a UNESCO World Heritage Site, in the context of flood protection, while taking into consideration the environmental, economic, and social dimension of heritage. The critical conclusions that are featured in the work indicate both areas of possible immediate remedial action and the potential directions that new integrated protection strategies would take.

Sustainable rainwater management is made possible, among others, by nationwide and local policies and regulations that create economic incentives. This article analyzes how existing economic instruments in Poland motivate property owners to make investments that manage rainwater on their own properties. Two types of investments were analyzed: bioswales as one of the lowest-cost green infrastructure measures in construction and operation, and the rainwater harvesting solution that uses rainwater to irrigate greenery. Simulation of this type of investment was undertaken in response to existing economic incentives—obtainable discounts of national and municipal rainwater drainage fees and municipal subsidy programs for rainwater management from three cities of different sizes selected from the Greater Poland province. Analyses were carried out for three types of development: different intensity, sealing of the land, and number of residents. The financial profitability of the investment was evaluated by determining the payback period, NPV, and benefit–cost ratio, taking into account the possible discounts in fees and investment subsidies in the variant analyses. It was shown that the incentive function of national fees for rainwater drainage is low, and that the incentive function of municipal fees and subsidies is higher, depending on the design of the fee (rates and discounts) and subsidy (directions and level of subsidies) systems.

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.