Every drop counts

Managing every drop

There is an expression used to describe when a small contribution, seemingly insignificant on its own, adds up with others to exceed the capacity of a system. In English, this is often expressed as the straw that broke the camel’s back. Every language has its own figurative image for the same idea. In Italian, it is described as “la goccia che fa traboccare il vaso”, meaning the single drop which, falling into a container already filled with countless others, is the one that causes it to spill over.

If we extend this image to the torrential rains that are becoming increasingly frequent in the current climate emergency, we understand how the management of each drop can contribute to the resilience of our territories. With the increase in intense rainfall events, the likelihood grows that the capacity of our drainage systems will be exceeded and that from a certain drop onward, all the following ones will overflow. Once this water escapes the drainage infrastructure, it floods, disrupts, and damages everything in its path.

It is therefore essential not only to repair and expand the drainage system to increase its efficiency and capacity, but also to intercept every drop that falls on the territory before it collectively reaches rivers and exceeds their thresholds. AQUAGREEN is a project centred on managing every drop falling on a pilot area in Faenza. It aims to ensure that each drop is intercepted, directed, stored, reused, and used as close as possible to where it lands. The project seeks to develop innovative systems for urban areas, so that water management becomes part of the everyday urban environment and every space contributes to better rainfall management.

A fragile territory

A simple rule helps us understand why rainfall patterns today are different from the past: the warmer the atmosphere, the more water vapour it can hold. For every additional degree of temperature, it is estimated that the air can retain about 7 per cent more humidity. Considering that the global average temperature has already increased by approximately 1.4°C compared to pre-industrial levels, the atmosphere now contains at least that 7 per cent more moisture than it did a century ago, as meteorologist Luca Mercalli points out. And all this water, sooner or later, has to fall. The question is how and where it does so.

Rainfall does not increase uniformly. It may rain very little in some areas and then fall in large volumes over a short period in a limited area. This is precisely what happened in Romagna. In May 2023, the region was struck by two flood events just two weeks apart, on the 3^rd and the 16^th of the month. Torrential rain, overflowing rivers, and entire areas inundated. An exceptional event repeated in September 2024, when a further extreme weather event brought even greater rainfall than in 2023, leaving little time for recovery or securing the territory.

These are not isolated episodes. They are part of a wider trend indicating an acceleration of extreme phenomena, driven by a increasingly warm and unstable climate. Romagna has, unfortunately, become one of the most recognisable cases of this trend.

The Romagna Faentina Union of Municipalities is located in the province of Ravenna, encompassing the territories of Faenza, Brisighella, Casola Valsenio, Castel Bolognese, Solarolo and Riolo Terme. It is an area lying across the hills and the plains, where fast-flowing rivers encounter densely urbanised areas with an artificial water regulation system. The combination of these factors means that during intense rainfall events, large volumes of surface runoff reach the plain’s river and canal systems in a very short time.

Faenza, for example, is crossed by the Lamone River, which just upstream from the city receives the waters of the Marzeno, a tributary with a torrential regime and heavily regulated course. It is not unusual for the Lamone to exceed alert levels, leaving many neighbourhoods in suspense as they await the flood peak to pass. However, climate change in this area also means higher summer temperatures and greater precipitation variability, which sometimes results in prolonged drought periods during which water resources become precious.

From emergency to transformative solutions

For a territory struck by a flood like those that hit Romagna, many approaches contribute to reducing risk and limiting damage. Experts often speak of a "risk management cycle," because it’s not just about reacting to the emergency: it’s also about preparing in advance, responding effectively during the crisis, and taking wise action afterwards to reduce the impact of future events.

The first and most visible line of defence consists of infrastructures: levees, flood retention basins, dams, and spillways. These are designed to contain or divert excess water, protecting cities, farmland, and homes. However, updating and maintaining such structures takes time, which is something that is increasingly scarce, as extreme events become more frequent and intense.

Just before and during an emergency, rapid and operational responses are activated, including mobile barriers and pumps, along with organisational measures such as weather alert systems, evacuation plans, and coordination among civil protection agencies, municipalities, and volunteers.

After a flood, the emergency phase continues with structural restoration work on roads, bridges, and embankments, as well as economic compensation tools like reconstruction funds, aid for families and businesses, and climate damage insurance.

The AQUAGREEN project operates in the delicate phase where the emergency is coming to an end, and, as things get back to normal, we also need to change the old way of thinking that led to the crisis, so we can deal with future climate events and restore people's trust. The project does this by testing new technical, social, and decision-making tools for integrated stormwater management, an approach that combines engineering, urban planning, ecology, and citizen participation. It aims to transform cities into more resilient systems, addressing the challenges of both water excess and scarcity and the rising temperatures brought by climate change.

Technical, social, and decision-making solutions

Among the systems AQUAGREEN is testing, one is focused on managing rainfall and treating it as a resource through green and blue infrastructure. The test site is a 3.5-hectare area in Borgo Durbecco, a neighbourhood that suffered heavy flood damage and has a morphology that naturally tends to retain water. In this area, Sustainable Urban Drainage Systems (SUDS) are being designed, tested, and monitored to perform key hydrological functions such as infiltration, retention, reuse and slowing of intense rainfall. The technical solutions include permeable pavements, sub-base storage layers, rain gardens, green roofs, underground tanks, and temporary urban basins. These elements are being sized and designed to work as an integrated system, where each part serves a specific water management function, and together they can handle runoff during heavy rain events and reuse water for irrigation during dry periods. This dual function is crucial to support the health of vegetation integrated into these nature-based solutions (NBS), which also help reduce the high temperatures reached during summer heatwaves.

This urban area, which includes a parking lot, a sports facility, and a public park, is being imagined as a multifunctional resilience park (MRP), where the effectiveness of these solutions is tested and monitored over time through sensors and digital tools. It serves as a living lab (LL), where innovation does not end with implementation but continues to evolve. From a technical point of view, the experience and knowledge gained will inform other urban projects and intervention systems, as well as other European cities, paving the way for replicating the most effective solutions and making runoff management a core element of urban design.

However, the purpose of the living lab is also social, because it allows the community to regain a sense of normality and cohesion. This is why local stakeholder engagement has already started, and various citizen participation activities are planned. These include co-design workshops for specific interventions and the management of activities that will take place within the park, as well as creating a multi-functional facility that will collect data and serve as a space to raise awareness among residents about the effectiveness of the measures.

Other planned innovations will build resilience and connect to the broader risk management cycle. The first is an early warning system, a predictive model fed by real-time data capable of integrating with extreme weather forecasting tools. This innovation supports preparedness and anticipation, enabling rapid emergency activation when time becomes a critical factor. The second innovation focuses on integrating real-time data and project-generated knowledge into a decision support system for urban planning and risk identification, scalable to the entire area covered by the local union of municipalities.

The AQUAGREEN project officially started just before 2025 and will continue to evolve through multiple phases. Future updates will provide deeper insights and highlight innovations as the project advances, shedding light on new ways to build urban resilience in the face of climate change.