In urban environments, three distinct water systems can typically be identified: (1) the drinking water supply, (2) the wastewater/sewer system, and (3) the rainwater/stormwater management system. While many cities are situated within urban watersheds, urban development has a significant impact on urban hydrology-associated environments, including waterways, coastal waters, and water supply catchments. Managing water flows within an urban setting is critically important, as original natural ecosystems have undergone significant land changes alongside anticipated precipitation variations due to climate change. It is imperative for urban areas situated on or near waterfronts to prioritize this matter. Therefore, water-sensitive urban planning and design framework integrating Nature-based Solutions in coastal, delta, and riverine cities within urban watersheds. It is similar to Green Infrastructure and/or Stormwater Best Management Practices, as well as Low-Impact Development, and the Water Sensitive Urban Design concept, which is an innovative framework for urban planning and design. It has evolved from its initial focus on stormwater management to encompass a more comprehensive approach to sustainable urban water management. It offers a cohesive framework for integrating the interactions between the built environment, including urban landscapes and the urban water cycle.
Colombo, the commercial and financial hub of Sri Lanka, faces significant challenges due to its aging and congested urban infrastructure. The city is built on thirty-six wetland patches linked by a 50-kilometer man-made canal system called the Colombo Wetland Complex (CWC). Due to its strong connection with its wetland complex, Colombo City was recognized as the first capital to be accredited as an International Wetland City by Ramsar in 2018. The CWC includes open-water lakes, a canal system, wet woodlands, herb-dominated areas, riverine forests, active and abandoned paddy fields, and reedbeds. These wetlands provide crucial ecosystem services, enhancing residents' well-being through water purification, urban flood mitigation, temperature regulation, recreational opportunities, and urban agriculture. Revitalizing and developing the city, as well as encroachments, has led to the loss of its natural mosaic and ecosystem services. It is essential to explore sustainable solutions that address significant urban water management issues, including stormwater, wastewater, and groundwater.
