The Kallang River is no Kinabatangan or Mekong River. For most of its length, it is a narrow concrete canal that connects Lower Peirce Reservoir to Marina Reservoir. However, a stretch of the river that runs through Bishan-Ang Mo Kio Park has been naturalised, turning it into a breathtaking force of nature at the heart of our concrete jungle. And with the restoration of this river, the surrounding landscape was brought to life. In September 2023, our NUS GE3255 Aquatic, Riparian and Coastal Systems class explored this reach of the Kallang River with Prof. Gretchen and our TA Kyle.

Figure 1. A grey heron stands in the naturalised stretch of Kallang River (Photo by Teo Kate-Lyn).

The physical restructuring of the canal has involved replacing homogenous concrete surfaces with natural material such as rocks, soil, and vegetation. In addition, what was once a straight and narrow channel is now sinuous with varying widths, creating an array of flow patterns. These factors contribute to habitat complexity that attracts a variety of wildlife. Besides increasing the diversity of residential fauna (e.g. purple herons, waterhens, and dragonflies), the restored river is known to draw migratory bird visitors as well.

Figure 2. Vegetation by the riverbank (Photo by Teo Kate-Lyn).

Amazingly, the vegetation growing along the river acts as a natural filter against pollutants and excess nutrients in the water that flows off surrounding land. The roots of these plants also play a key role in stabilising the riverbanks by reducing erosion. However, this restored river lacks trees that would be found along the banks of a natural river, and is thus missing a critical source of erosion control. As an alternative, soil bioengineering techniques such as riprap, gabions and bioswale are employed.

Figure 3. Soil bioengineering: Riprap, a cluster of small rocks along the bank (Photo by Teo Kate-Lyn).

During a heavy downpour or storm, the capacity of the riverbanks may be exceeded. This is when the wide, flat swathes of land by either side of it flood. These are known as floodplains, and they act as a secondary channel to help carry the large volume of water downstream. The meandering nature of the river and its adjacent floodplains all work to slow the passage of water through this channel, protecting surrounding and downstream urbanised areas against floods.

Restoration projects such as this require plenty of time, money, and labour, which may be why they are so rarely undertaken. However, when successful, we save more costs by avoiding the damage caused by frequent flooding, and create a beautiful, biodiverse, and resilient ecosystem that boundlessly benefits both us and nature.

Figure 4. Adjacent naturalised and non-naturalised sections of the Kallang River (Photo by Teo Kate-Lyn).