Design with nature (revisited): How a rain garden design, construction, and post-construction monitoring program promotes eco-literacy in Singapore

In his seminal 1969 book, Design with Nature, landscape architect Ian McHarg argued that science and ecology must underpin and direct regional and urban development so that even in existing cities we “…see the components of the natural identity of the city as a value system, offering opportunities for human use…It is, therefore, essential to understand the city as a form, derived in the first instance from geological and biological evolution, existing as a sum of natural processes and adapted by man.” Partly, McHarg’s work was a blueprint for ecological or eco-city planning that has evolved to embrace more recent planning concepts such as Water Sensitive Urban Design (or Low Impact Development, or Sustainable Urban Drainage Systems) that have served to enhance urban liveability. As an island-state with limited catchment area, Singapore has been at the forefront of implementing innovative and sustainable water management, particularly in recent years through the Public Utility Board’s (PUB) Active, Beautiful, Clean Waters (ABC Waters) programme. The ABC programme seeks to improve the quality of water and liveability in Singapore by harnessing the full potential of its waterbodies through a holistic integration of its stormwater drains, canals and reservoirs with the surrounding environment. The PUB has aggressively promoted and implemented a number of Water Sensitive Urban Design (WSUD) technologies at more than 62 large scale projects since 2010, including green roofs, green walls, raingardens, cleansing biotopes, pervious pavement, constructed wetlands, and floating wetlands, which effectively connect the land and water environments. The private development sector in Singapore also actively employs WSUD technologies.

As part of a recent outreach and education programme the PUB is constructing 8 raingardens at primary and secondary schools, junior colleges, a polytech, and the National Institute of Education (NIE), Nanyang Technological University. Undergraduates at NIE are pre-service teachers and therefore will take their experiences to Singapore classrooms upon graduation. The raingarden constructed at NIE is large, with a surface area of 220 m² (including 45 m² of filter area) and a ponding depth of 1 m (designed to accommodate a 3 month storm). The design includes 4 substrate layers, with the 450 mm deep surface layer of loamy soil subsequently draining to a layer of coarse sand and wood chips (to provide anaerobic conditions and enhance nitrogen treatment), and subsequently layers of coarse sands and clean gravels. The total substrate layer depth is 850 mm. Primary drainage is via a 150 mm diameter underdrain leading to a local surface drainage canal. NIE has installed monitoring instrumentation, including a meteorologic station, water level, conductivity and dissolved oxygen sensors in the concrete chamber leading to the underdrain, and sampling tubes connected to a pump that facilitates sampling for water quality at the different substrate depths.

Eco-literacy is an important component of the Singapore school curriculum and a key element of the NIE Geography Department’s signature programme, the Sustainability Learning Lab (SLL). To date, the raingarden has had a central role in eco-literacy training of NIE’s pre-service teachers, as classes for one cohort included assignments to conduct site suitability assessments prior to construction, a lecture about raingarden design by the design team, and observation of the construction process. A subsequent cohort class assignment is analyzing the initial physical and biological properties of the raingarden (e.g. substrate texture, infiltration rate, plant type and viability) and installing and calibrating the weir for the water level measurements. Future classes will sample and assess the water quality and water movement through the raingarden as well as monitoring plant viability. All monitoring and analyses are linked to the Singapore curriculum. For example, the Secondary Geography curriculum considers fieldwork and critical thinking investigations to assess water quality of local waterbodies and issues of urban flood, including measures that can be taken to manage flooding. WSUD technologies, including the raingarden are being used as field-based case studies for the students. Later in 2017, in-service teacher training courses that feature the raingarden also will be offered.

In this paper we review the design of the NIE raingarden, how the NIE students were involved in all aspects of the raingarden development as part of their educational experience, as well as presenting some of the preliminary monitoring results. In conclusion, WSUD technologies such as raingardens attempt to mimic pre-development hydrology and as such we argue this is one path of evolution in designing with nature. Ultimately, our goal is to reconnect with and enhance McHarg’s ideas about the importance of science and ecology in promoting urban liveability and improve eco-literacy in Singapore through authentic and hands-on learning experiences.