Beddagana wetland Park in western province, outside of Colombo. Photo by Sureshkumar1213. CC.

Need of geospatial analysis on further strengthening water sensitive urban planning and design to stormwater management in the Greater Colombo metropolitan area

Published on 29 May 2025 , by Padmi Ranasinghe

Need of geospatial analysis on further strengthening water sensitive urban planning and design to stormwater management in the Greater Colombo metropolitan area

Published on 29 May 2025 , by Padmi Ranasinghe

Challenge-ID

Description

Photo: Beddagana wetland Park in western province, outside of Colombo. Photo by Sureshkumar1213. CC.

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.

Has this problem been acknowledged in the past?

Very rarely. I have faced this problem often in my research.

Can this challenge be solved using space technologies and data?

I believe so. It needs spatial distribution.

Expected timeframe to develop a solution

8 months

Potential consequences if no action happens

Will have to depend on whatever available data.

What are additional physical requirements for a solution?

If no geospatial analysis is not available, we have to select a smaller area, which is possible to cover the physical observation.

Problem Definition

Science-based policies and planning are crucial for the conservation, restoration, and effective management of ecosystems and urban water bodies. Geospatial analysis has become a powerful tool that enables decision-makers to visualize the evolution of land reclamation and land use, as well as their impact on the natural environment. However, as fast urbanization occurs in cities, fragmented wetlands, isolated small waterbodies, or ecosystems are hard to identify through common geospatial analyses such as NDVI, EVI, or WDVI, or may not be accurately represented. Most satellite images are based on a pixel resolution of 30 meters (Landsat 9) or 10 meters (Sentinel-2). However, since the fragmented freshwater wetland areas are so small in some parts of the Colombo Wetland system, the resolution of the analysis may not be accurate. Therefore, this challenge presents an opportunity to incorporate other possible Geospatial analysis tools to identify small-scale, fragmented Natural areas and freshwater wetlands, other urban waterbodies, and /or Water Sensitive Urban Designs (WSUD) like green roofs, bioswales, rain gardens, constructed wetlands, tree planters, and bio-retention spaces, at a low cost. This will support the creation of effective urban design plans and policies for sustainable urban water management.

Success criteria

To incorporate accurate, low-cost geospatial tools (other than common NVDI, WDVI, etc.) and analysis for small-scale water-sensitive urban designs, including freshwater wetlands, riverine forests, green roofs, bioswales, rain gardens, constructed wetlands, tree planters, and bio-retention spaces, etc. through space-based data. These can create accurate and efficient urban planning, designs, and policies for sustainable urban water management.

This will provide accurate information to assess the intensity of fragmentation, present wetland eco-connectivity, and waterbodies, thereby mitigating urban flooding and other water issues in the Colombo metropolitan areas while conserving, restoring, and managing the wetland complex.

Thematic focus area

urban stormwater management

Relevant data sources/publications

IWMI. “Urban wetlands and the built environment: how Colombo’s green spaces enhance city life - IWMI.” 2024. https://www.iwmi.org/news/colombo-wetlands-and-the-built-environment/.