Case Study

Rain Garden Evozone in the Philippines

Posted: 06 March 2025

Updated: 06 March 2025

Asia - Philippines

Issue

The Philippines experiences frequent typhoons and other heavy rainfall events which can cause major flooding. Forests and other natural/semi-natural ecosystems can help to absorb rainfall and reduce flooding. The Santa Rosa Watershed, in which Santa Rosa City is located, has lost much of its natural and semi-natural ecosystems in recent decades due to urban expansion, and even further losses are expected in the future (Johnson et al., 2015). Flood hazards are expected to increase in the future due to these land-use changes as well as climate change (Bragais et al., 2017). Thus, creating or restoring natural or semi-natural ecosystems in strategic locations of the watershed can provide a way to reduce flooding and also enhance local biodiversity.

Solution

Nature-based solutions are commonly used to conserve biodiversity while also addressing local problems like flooding (Debele et al., 2019). They may include conserving/restoring existing natural ecosystems, or developing new natural or semi-natural ecosystems (Dorst et al., 2019). Rain gardens are a type of semi-natural ecosystem that can provide flood management services and also be used for recreational purposes (hiking, biking, birdwatching, etc.), while also helping to conserve/enhance local biodiversity. A key feature of rain gardens is that they are located on a lower elevation than the surrounding land, forming a depression that can be filled with rainwater. By collecting and storing the rainwater, they can reduce flooding in other areas nearby.

Description (Details)

Rain Garden Evozone is approximately 3.2 hectares and has been developed as a rainwater catchment basin as well as an eco-tourism location for local residents (https://www.nuvali.ph/explore/rain-garden-evozone/). It was developed by the same company that built the NUVALI eco-city (a large, mixed land-use development), in which the rain garden is situated. The Santa Rosa City government has emphasized the need for developers to incorporate stormwater management infrastructure in new development projects (Johnson et al., 2021), and Rain Garden Evozone provides an example of how developers can accomplish this.

Here, the site and its development history are shown using high-resolution images from Google Earth. Prior to the development, the site was mainly covered by grass and shrubs (Figure 1). Land clearing and construction work on the commercial area and rain garden began around 2008 (Figure 2), and was completed in 2014 (Figure 3). As can be seen in Figure 4, during drier periods of the year, the water level drops in the rain garden due to natural evaporation as well as water harvesting/irrigation of the nearby areas. Thus, it can provide valuable ecosystem services in both the wet season (flood management) and dry season (water for irrigation).

In terms of the vegetation, the rain garden reportedly contains over 20 bamboo varieties, seven types of trees, and various grasses, all of which serve as habitat for at least six bird species (https://rpnradio.com/go-straight-to-a-southern-sanctuary/?amp=1). There are various open areas and trails on the site that can be used for recreational activities like hiking, biking, yoga, and birdwatching (https://www.nuvali.ph/explore/rain-garden-evozone/).

Reports

Bragais, M. A., Johnson, B. A., Onishi, A., Endo, I., & Magcale-Macandog, D. B. (2017). Flood extent of different land-use scenarios under event-based precipitation in Silang-Sta. Rosa subwatershed, Philippines. Institute for Global Environmental Strategies.

Debele, S. E., Kumar, P., Sahani, J., Marti-cardona, B., Mickovski, S. B., Leo, L. S., Porcù, F., Bertini, F., Montesi, D., Vojinovic, Z., & Di, S. (2019). Nature-based solutions for hydro-meteorological hazards: Revised concepts , classification schemes and databases. Environmental Research, 179(August), 108799. https://doi.org/10.1016/j.envres.2019.108799.