## 4 A Case Study  
Located in the centre of Portugal, about 150 km north of Lisbon, Leiria is of great economic, environmental and social importance and plays a strategic role in the national context of sustainable development. The geographical location of the region is a pertinent factor in understanding its vulnerability to climate change [58; 59; 60]. The city partly extends over the floodplains of the Lis and Lena rivers, which exposes it to flooding and erosion risks [58; 59], while its proximity to the coast exposes it to saltwater intrusion and the effects of rising sea levels [60]. Additionally, the region's extensive forest cover, essential for biodiversity and ecological balance, also heightens the risk of wildfires, especially during severe droughts [60]. Since the 1990s, Leiria's population has grown by around 25% [61], driving urbanisation and increasing pressure on water resources. This growth has created significant challenges--including increased pollution of watercourses, an increased risk of urban flooding, and water scarcity--all of which are exacerbated by extreme weather events [58; 59; 60]. Issues such as the artificial occupation of riverbanks, fragmentation of aquatic habitats, and point and diffuse pollution are highlighted in strategic reports like the Strategic Plan for the Rehabilitation of Water Lines and the Municipal Climate Change Adaptation Plan for Leiria. In this context, it is essential to develop integrated water management strategies that ensure efficient and resilient use of water resources, in line with local needs and sustainable urban planning. Recognising Leiria's environmental and social significance, this study examines the Detailed Urbanisation Plan for Sao Romao/Olhalvas--a strategic initiative under the Polish Programme aimed at revitalising the banks of the River Lis. The project aims to redefine the urban environment by fully integrating the River Lis and its margins into the urban fabric, thereby enhancing the river as a central territorial landmark [62]. To achieve this, the plan proposes creating an extensive green corridor with interconnected pedestrian and cycle routes, as well as multifunctional spaces for recreation, leisure, and community gatherings. It also proposes the creation of urban parks, public gardens, and agricultural zones for organic production and ecotourism, all contributing to a balanced urban ecosystem. Complementary infrastructure, such as sports facilities (e.g., tennis courts) and car parks, is also planned to support community activities and urban mobility. The redevelopment strategy extends to the riverfront itself, with plans to upgrade urban service networks and construct new buildings for residential, commercial, and service uses, all designed to meet high architectural standards and blend seamlessly into the local landscape. Key technical features include a managed floodplain with a naturalised water surface and a purpose-built weir, which serves as a retention basin for flood control and stormwater management. In addition, the strategic location of the Sao Romao Wastewater Treatment Plant in this area reinforces the project's commitment to sustainable water management and environmental protection [63]. The data presented in Table 8 summarise the key elements of the Sao Romao/Olhalvas Detailed Plan, highlighting the spaces and infrastructures intended for the requalification and development of the area. \begin{table}
\begin{tabular}{l l} \hline \hline
**Description** & **Value** \\ \hline Intervention area & 41.40 ha \\ Total construction area for housing, commerce, and services & 46,828 m\({}^{2}\) \\ Proposed construction area for car parking & 11,421 m\({}^{2}\) \\ Proposed construction area for equipment and support buildings & 6475 m\({}^{2}\) \\ Number of dwellings (total) & 242 \\ Total area of public green areas and green spaces for collective use & 86,409 m\({}^{2}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Summary of the São Romao/Olhalvas Urbanisation Detailed Plan [63].