Davao City’s Rapid Urbanization:
Davao City has become one the the Philippine’s fasts-growing cities, with a reputation for safety, discipline, cultural diversity, livable geography, and high-quality water resources … attracting both national and international people. The city is home to 1.6 M people, with a 2.3% annual population growth, and is considered the third most populated city in the Philippines. Population increase has led to an increase in the construction of residential, commercial, industrial, and institutional establishments in both urban and rural areas. This has caused flooding and inability to recharge ground waters and aquifers, consequently resulting in conversations about impermeable surfaces in which rainfall cannot infiltrate naturally.
The Interface Development Interventions, Inc. (IDIS), an environmental non-government organization (NGO) in Davao, continues to push for an ordinance requiring both public and private establishments to use permeable pavements as part of urban sustainable initiatives. The IDIS is calling for local researches and studies in line with the Sustainable
Development Goals with the categories:
- Renewable energy
- Zero wastes
- Healthy watersheds
- Sustainable agriculture
- Disaster resilience
- Green communities
Permeable Pavements:
Due to the natural landscape changes in urban areas, the city’s drainage system has been put into overload resulting in flooding. Green spaces have had to be preserved as much as possible to reduce rainwater run-off to maintain balance in the ecosystem. With the rainy season, the streets have flooded and inconvenienced many people, so a proposed ordinance seeks the solution of permeable pavements—a water management system that allows water to move through porous spaces within the pavement and eventually infiltrate into underlying soil. They are the sustainable alternative for low-traffic roads, patios, plazas, parking spaces, driveways, bicycle lanes, pedestrian walkways, and home garages.
Many countries use permeable pavements for multiple benefits. There are different types which are widely used in the global market with main differences being porous space, spatial arrangement of the underlying pervious layers, and structural strength. Since its origin, the concept of permeable pavements was developed to reduce floods, reduce rising water tables, replenish aquifers, reduce runoff volume, mitigate runoff peaks, and sequester many forms of pollution.
Such rapid urban development poses ecological disadvantages, but permeable paving offers a range of ecological benefits. See image to the right:
The IDIS conducted research on establishments using permeable pavements in the central business district of Davao City, and results confirmed the manifold benefits of this technology from reducing surface water runoff to trapping CO2 and surface cooling. Permeable pavement has proven to be a technology seen to help reduce floods in Davao’s urban centers and add more green spaces to the city. Out of the 20 establishments surveyed, 5 were selected as case studies based on the availability of documents and cooperation of the management. The establishments represented varied business types and land uses:
- Small-scale commercial lodging
- Small-scale commercial restaurants
- Large-scale offices
- Educational institutions
- Industrial and manufacturing facilities
Five types of permeable pavements were assessed based on the data gathered. For typologies not covered in the case study, a landscape expert, an environmental architect, and existing studies were consulted. Of the 20 establishments, 80% used permeable pavements in their entrances, patios, sidewalks, driveways, low-traffic roads, and parking lots. They reported results of the permeable pavements, post construction:
- No major flooding
- Helped manage storm water runoff
- Affirmed they reduced urban heat effect especially during hot or dry seasons
- Contributed to the good condition of the urban eco system
The project is not just limited to its aesthetic benefits but can also be beneficial economically like:
- Groundwater recharge
- Minor evapotranspiration losses
- Surface light reflectivity
- Visual improvement in porous spaces with vegetation
- Cost elimination for retention basins, curbs, gutters, and other water collection installations
- Lower installation costs-no underground piping, storm drains, or sloping/grading needed
- Lower life-cycle costs due to equal life of concrete: 20-40 years
- Combine infiltration and pavement, reducing drainage canals
- Create green space, equaling shade/groundcover
Research Presentation Highlights:
Lemuel Ibanez-Manalo, Environmental Research Specialist-IDIS, debunked the premise that permeable pavements are expensive and only offer environmental benefits. He said they were advocating and promoting the permeable pavement designs because they believe that this design would absorb flood waters as well as filter and trap pollutants.
“Many of the establishments here in Davao are using the project already and we continue to maximize this through the use of media to advocate the product and promote the design… since there’re a lot of benefits like mitigation of floods, decrease on eye sore, and decreasing the urban island heat effect,” Manalo said. “We are doing our largest efforts to attract them [the young architects] for this technology. We started mainstreaming this last year, there were articles posted already and we already provided data for this project in the internet,” he added.
Mark Peñalver, Attorney and Policy Advocacy Specialist-IDIS, said there are no ordinances and policies in place yet concerning the permeable pavement, but there are responsive city councilors open to sponsor the proposed policy such as Mabel Acosta, City Councilor-Davao City.
“We cannot stop urbanization, but we need to mitigate measures so that sustainable development can be attained. I welcome the options that permeable technology offer—environment and progress can go together,” said Acosta.
Fermin Edillon, Community Relations Manager-Davao Light and Power Co., Inc. (DLPC) said, “I used to think permeable pavements were purely aesthetic. It’s only when we started using them that we realized their benefits. We need to intensify [communication with the] International Electrotechnical Commission (IEC) on this since not many people know the value of this technology.”
The study concluded that Davao City is pushing toward sustainable growth, the City Government should maximize permeable pavements as a valuable alternative and simple strategy to spare more “true open spaces” for the city. This study showed that permeable pavements have the potential to produce economic savings for the city’s sewage systems and is a solid investment for the city’s disaster risk reduction and management, due to reduced flooding.
Other Resources:
4-page Report PDF titled “Mainstreaming Permeable Pavements: Eco-Friendly Paving Alternatives in Keeping Davao City Green and Sustainable”, please go to: http://idisphil.org/wp-content/uploads/2018/04/KINAIYAHAN-NL-17.pdf
IDIS website (leads to PDF): http://idisphil.org/2018/04/10/bk-on-permeable-pavements/
Sunstar Davao article titled “Group pushes use of permeable pavements”: https://www.sunstar.com.ph/article/1742742
Sunstar Philippines article titled “Hidalgo: Of durian and caves”: https://www.sunstar.com.ph/article/1756650/Davao/Opinion/Hidalgo-Of-durian-and-caves