CH2M HILL transforms Singapore's Alexandra Canal
Integrating Singapore's water bodies into the urban landscape in new and innovative ways is the goal of national water agency PUB. Under its 'Active, Beautiful, Clean Waters' (ABC Waters) programme, a 1.2 km stretch of Alexandra Canal from Tanglin Road continuing downstream to Delta Road was transformed from a functional concrete canal into a pleasant and attractive waterway with softened banks, seamlessly integrated with the adjacent surroundings. CH2M HILL is the principal consultant involved in the project design and the redeveloped canal was opened on 19th March 2011.
This section of Alexandra Canal starts from an elevated lookout deck at Tanglin Road in which gentle ramps lead down to the new structural deck. A water cascade coming down from the elevated deck flows into a shallow stream which meanders into a water play area. At the end of the water play area is an Educational Hut, showcasing panels about water. The shallow stream then gives way to a set of wetlands which naturally treat water from the canal, and provide opportunities for outdoor classroom learning. This is a tranquil area with simple boardwalks and intermittent resting points so people can get close to water and nature. The water in the wetlands is pumped from the canal and cleansed water at the end of the wetlands will trickle through a rockscape area before flowing back into the canal.
Part of the existing concrete wall of the canal was removed to create a setback for soft planting, transforming the waterway from a functional drain into a modern canal with softer edges and nodes that extend out to adjacent urban developments. A community plaza suitable for community activities was constructed at the downstream of the canal, providing a great lookout point for views of the waterway.
The wetland modules designed for this project are surface flow, floating aquatic vegetation and horizontal sub-surface flow. In addition, rain gardens, vegetated swales and bio-retention swales form sustainable natural elements that attenuate and improve the quality of rainwater runoff. The pilot-scale implementation of these various features are also good demonstration tools to educate the public on the feasibility and effectiveness of treating rainwater where it falls, which should not be overlooked in a densely populated urban city such as Singapore.