Sustainable rainwater management: a decisive factor in urban infrastructure decision-making

Paradigm Shift in Urban Infrastructure: From Pipes to Blue-Green Systems

Climate pressures facing cities worldwide are reshaping infrastructure investment logic. Traditional stormwater management systems centered on drainage pipes and culverts, while effective in mitigating waterlogging over the past century, struggle to cope with increasingly frequent extreme rainfall, urban heat island effects, and water quality degradation. Sustainable Stormwater Management (SSWM) has emerged, integrating blue-green infrastructure into the urban fabric through decentralized facilities that mimic natural hydrological cycles—such as rain gardens, detention wetlands, and permeable pavements. This shift involves not just an upgrade in engineering technology but a fundamental restructuring of governance, financing models, and long-term operations.

Swedish Case: Governance Conditions Outweigh Technical Performance

A recent study published in *npj Urban Sustainability* examined two Swedish cities, Malmö and Östersund, systematically reviewing 40 factors influencing stormwater management since the 1960s and ranking nine key factors by priority using the Best-Worst Method with practitioners. The results were surprising: "External collaboration" was deemed the most decisive factor, while "technological innovation and adaptation" ranked last. This means that when facing future SSWM decisions, practitioners believe that while system performance expectations are important, "delivery conditions"—such as cross-organizational coordination, policy authorization, institutional capacity, land-use negotiation, funding sustainability, and long-term maintenance—are the real levers determining success or failure.

This finding challenges the traditional infrastructure assessment tendency to over-rely on modeling and quantitative performance metrics. In Malmö and Östersund, despite differences in scale and climate, institutional fragmentation and unclear responsibilities emerged as the greatest obstacles to SSWM adoption. When multiple departments—municipal water services, planning, parks, transportation, and private landowners—need to jointly manage a stormwater treatment system, a lack of coordination mechanisms leads to project delays, cost overruns, and even functional failure.

A Mirror to Global Infrastructure: Why SSWM Is the Next Investment Frontier

From a broad global infrastructure perspective, the challenges facing SSWM are not unique. Similar "institutional lock-in" phenomena appear in energy transition, smart cities, digital infrastructure, and other fields: entrenched engineering inertia and sectoral interests make it difficult for new technologies to cross the threshold. However, SSWM is unique in that it involves nearly all urban infrastructure sectors—transportation (permeable pavements), buildings (green roofs), public spaces (rain gardens), water treatment (pipe connections)—so its success directly determines overall urban resilience.

For infrastructure investors and project financiers, SSWM projects have distinct appeal: they are typically moderate in scale, modular in deployment, and generate multiple benefits (flood control, ecology, climate regulation, health).For infrastructure investors and project financiers, SSWM projects have unique appeal: they are typically moderate in scale, can be deployed modularly, and generate multiple benefits (flood control, ecology, climate regulation, health). However, as the Swedish research institute has revealed, capital can only be effectively allocated when governance structures provide these projects with a stable policy environment and a cross-sector collaboration platform. The PPP model (Public-Private Partnership) has been attempted in this field, but the allocation of long-term maintenance responsibilities, the setting of performance indicators, and the cost recovery mechanism still require refined design.

From Nordic to Global South: Transferable Experiences and Challenges

Sweden’s experience offers greater reference value for developing countries. In rapidly urbanizing regions, such as Southeast Asia, India, and Africa, drainage systems are already weak, and building large-scale SSWM systems all at once is often unrealistic. At such times, prioritizing the establishment of institutional coordination capacity, creating cross-sector responsibility divisions, and building social trust through small-scale demonstration projects are more critical than introducing expensive technologies. The World Bank and the Asian Development Bank have in recent years listed “climate-resilient urban drainage” as a priority lending area, but project reviews should incorporate more governance capacity assessments.

It is worth noting that SSWM systems are not low-maintenance. Unlike traditional underground drains, blue-green infrastructure requires ongoing upkeep—removing sediment, pruning vegetation, and monitoring water quality. Without long-term operational funding and professional teams, these facilities may become mere landscape ornaments or even breeding grounds for mosquitoes. Therefore, any SSWM investment must simultaneously establish a dedicated maintenance fund, or achieve financial sustainability through integration into property fees, rainwater taxes, or similar mechanisms.

Conclusion: Rebalancing Infrastructure Decisions

Swedish research sends a clear signal: the future of sustainable stormwater management does not depend on whether we can invent more efficient filters or smarter sensors, but on whether we can break down departmental silos, establish long-term financing, and prioritize governance capacity over the halo of technology. For global infrastructure analysts, engineering capital, and national planners, this means that in future project evaluations, the “soft conditions” beyond the technical parameter sheets must be given a weight commensurate with their decisive role. When urban infrastructure truly shifts toward nature-based solutions, what we need is not only engineering innovation but also institutional innovation.