Located at the Eastern fringes of Bangkok in the suburban district of Prawet, approximately 6 kilometers from the Suvarnabhumi International Airport, lies The Metro-Forest Project. An ecological regeneration project designed as an outdoor exhibition space to cultivate environmental awareness and educate visitors about local forest ecology. The project, on an abandoned site, aimed to reclaim 2-hectares (4.75 acre) of valuable land and reverse the trends of suburban sprawl, urban heat island, and flood-prone developments through the incorporation of historically local (native and introduced) lowland tropical tree species.
History & Context
Initial analysis of the abandoned site showed signs of dredging for soil as the excavation created pits for illegal refuse dumping. In early 2012, the landscape architects were commissioned by the PTT Reforestation Institute to design a space for reforestation. Under initiatives set by the President/CEO of the Petroleum Authority of Thailand (PTT) and in commemoration to the forest stewardship efforts by the Royal Family and Her Royal Highness, Princess Maha Chakri Sirindhorn's, an ecological forest that reflected Bangkok’s former landscape looked to be created for public education and enjoyment. Saplings of trees once prominent during the Rama III & IV era (mid-19th century) were selected for initial planting as they had once established territorial populations around Bangkok during which time many districts were named after the dominant species of the area.
Construction began in May 2013 where approximately 37,000 cu.m of earthwork was introduced and graded with 6,000 cu.m of planting soil to create the engineered berms that would provide a suitable planting medium and terrain for the new urban forest. In addition, the berms lead to the creation of diverse micro-ecologies in such a relatively small space.
Planting for Succession: Methodologies, Techniques
To create a diverse forest ecology, the planting techniques of saplings by Dr. Akira Miyawaki were implemented to create optimal growing environments of lowland dipterocarp. Through collaboration with the landscape architects, forest ecologists, and contractors, raised berms were designed, engineered and constructed to provide porosity and prevent compaction. A pre-mixture of highly fertile, organic soil (3-parts Topsoil, 1-part Raw Rice Husk, 1-part Coconut Coir Dust, 1-part Chicken Manure) was used as a soil medium suitable for the lowland species saplings. The layout of the species was carefully grouped according to successional rate and appropriate water to ground surface level growing conditions. For example, species that thrive in brackish water, such as Barringtonia asiatica, were planted along the canal embankment. Species able to survive during intermittent flooding conditions were planted along the riparian edge. While atop the berms, a diverse mix of deciduous forest plants and lowland dipterocarp cover the area.
Approximately 60,000 trees of more than 279 unique species were planted on approximately 75% of the overall site. Planting locations for the trees were also carefully selected based on the type of coverage each successional group would provide. For the initial planting of saplings, a planting density of approximately 4 trees per square meter or a spacing of 50 centimeters was used to encourage natural selection of the first phase + successional period of the forest covering the constructed berms. In the remaining planted areas, the tree plantings were sparser to help control sightlines, open up views, and provide open space area around the exhibition center.
The planting design intent also looked to create a forest canopy of multiple layers that could be controlled through monitoring of plant coverage, moisture levels and nutrient levels. Maintenance of the site will look for the forest to manage itself, as no management is the best management. However, as the forest matures, a practice of rotational forestry through predictive-modeling or forecasting of its succession will be implemented as the continuously on-going project evolves over generations to come.
Forest in the City: At the Canopy Level
Natural forests are known to have dense canopies, comprising of branches, leaves, flowers, and fruits. The control of the canopy is critical to controlling the environment of the forest. Whether it is light, moisture, or canopy protection, the designers looked at the importance of creating a micro-climate for plants to thrive off of one another and any surrounding elements. Through similar earthwork grading principles developed by King Bhumipol in his Royal Forestry projects, a combination of water feature and terrain design attempts to lower the ambient temperature, increase moisture, while also being a design strategy to control the height of the canopy.
The earthwork design, serves as the backbone of the site’s new ecology, but also aims to improve the aesthetics of the forest and its canopy by the plant variety changes along the cross-section of the elevated berms. Control of the canopy and density of planting is crucial to the ambience and design intent of the landscape architects to create a forest of seclusion for visitors to escape from the concrete jungles of Bangkok and spend a few hours in the tree wilderness. After the canopy has reached maturation, the landscape architects intend to carve out a trail at the ground level to provide an experience revealing the understory. However, in the early stages of succession, guests may spend a majority of their time atop the skywalk + observation tower, which were designed to minimize disturbance of the burgeoning forest and allow close-up views of the maturing canopy.
At the canopy level, planting at the optimal density and maintaining that density is essential to allow the saplings to flourish while also providing enough canopy interception to reduce runoff and allow for rainwater infiltration. The infiltration of water on-site results in the recharge of the groundwater within the constructed berms. The eventual spreading canopy of trees in the forest will serve to shade guests as they trek across the elevated skywalks and meander down from the viewing tower back to the exhibition center.
Rejuvenate Places & People
From the waterfall & stream carved and formed by earth-berm mounding, to the skywalk, tower, and exhibitions carbon neutral design. The project, which received LEED Platinum NC, is truly a public outreach commitment by the PTT Reforestation Institute to inspire public awareness of forestry management and the importance of environmental stewardship in Thailand as the design by the Landscape Architects has become an extension of the rammed-earth exhibition center from indoors to outdoors. The site has also become a new habitat for fauna to establish their home and visitors to observe.
The Land Art inspired outdoor exhibition is intended to be a medium where the landscape will be constantly evolving so that visitors will always be welcomed by ‘new’ experiences during each visit. Able to experience the different levels of the canopy at the ground-level, along the skywalk, and within the observation tower, visitors will see Bangkok like never before. A natural wilderness that provides an educational and fun experience that could perhaps inspire urbanites to plant saplings and grow a forest in their own backyard.
Additional Project Credits:
Product Sources [required for built projects]: SOILS
Product Sources [required for built projects]: LIGHTING
Product Sources [required for built projects]: DRAINAGE/EROSION
Product Sources [required for built projects]: FENCES/GATES/WALLS
Product Sources [required for built projects]: IRRIGATION
Product Sources [required for built projects]: LUMBER/DECKING/EDGING
Product Sources [required for built projects]: GREEN ROOFS/LIVING WALLS