Urban Challenges Under Climate Change – Managing Sealed Surfaces

In the topographic catchment of the River Jadro, areas designated for construction—including terrain modifications causing impermeability—account for 38% of the land. This figure highlights intense urbanization pressure on the catchment's natural environment. Currently, stormwater drainage infrastructure remains largely undeveloped. Future climate change scenarios predict more frequent heavy rainfall events, which will inevitably increase surface runoff and the risk of flash floods. Furthermore, stormwater flowing through urbanized zones will worsen existing pollution, contaminating the River Jadro, its estuary, and the coastal waters of Kaštela Bay. Under the Interreg project "Change We Care," a GIS analysis assessed current imperviousness within the catchment's built environment to support the "Climate Change Adaptation Plan for the River Jadro." Imperviousness data for urban surfaces were derived from the Copernicus Land Monitoring Service using the Imperviousness Density Status Layer and categorized by planned land use. Results indicate that within Solin’s administrative boundaries, built-up mixed-use areas possess 50% impervious surfaces. Conversely, in the Municipality of Klis, only 13% of the built-up area is impervious. However, urban regulations allow building plots to reach 80% imperviousness. Consequently, a rise in impervious surfaces to this maximum is probable, a trend already visible in commercial zones. Historically, artificial concrete banks were constructed along the Jadro’s middle and lower courses, disrupting the river's natural characteristics. Given the negative impacts of these anthropogenic changes, restoring river ecosystems is essential. Renaturalizing the main watercourse and its tributaries would significantly enhance regional sustainability. Because the natural and built environments are functionally intertwined, problem-solving requires an integrated approach that combines water management for the Jadro system with Solin’s urban water infrastructure. Therefore, the "Climate Change Adaptation Plan for the River Jadro" recommends mitigating urbanization impacts by strengthening natural components within urban spaces. Key measures include revising allowable impervious surface limits and differentiating permeability parameters by construction zone based on geological and topographic features. The plan also suggests introducing financial incentives for sustainable, ecological solutions. Physical interventions should include renaturalizing parts of the Jadro and its tributaries, protecting against coastal flooding by securing retention areas, and creating a "green-blue heart" in Solin and Klis by upgrading projects with Nature-based Solutions. Today, the DesirMED project is expanding these measures into an integrated management approach for the entire Kaštela Bay area in light of climate change. By collaborating with local stakeholders, a shared vision has been defined. Development is currently underway for adaptation pathways that feature a portfolio of innovative solutions, with a distinct priority placed on Nature-based Solutions to ensure long-term resilience. This evolution from specific river management to a broader bay-wide strategy represents a critical step forward. It acknowledges that effective climate adaptation requires looking beyond immediate municipal borders to encompass the wider hydrological and ecological context of the entire basin. Through these combined efforts, the region aims to balance necessary urban development with the urgent need for environmental preservation and climate resilience.