Closing the Loop: Integrating Stormwater Management for Climate Resiliency

Student: CHAN Ka Yu Phoebe

Supervisor: Susanne Trumpf
Thesis section: Man-made Ecologies: Interpreting Layers of Urban Landscapes
Programme: Master of Landscape Architecture
Date: June 2020


Freshwater supply in Hong Kong is climate dependent and it is uncertain upon the changing climate. Since 1965, Hong Kong has been importing freshwater from Dongjiang (East River) as the major water source, contributing 70-80% of current consumption. Local yield from protected catchment becomes the remaining and secondary source of supply. This thesis criticizes the conservative water policies and fragmented management framework in Hong Kong. The growing reliance on imported water has led to inertia of long-term freshwater sufficiency. With a projection of increasing rainfall yet longer drought period, there is a need to cater stormwater drainage and freshwater stability to enhance climate resiliency. Meanwhile, almost 90% of rainwater are discharged as stormwater to waste under separate management parties. A potential is observed to increase rainwater harvesting as alternative water supply through integration of freshwater and stormwater management. This thesis attempts to explore the potential of using stormwater as new freshwater sources for domestic water use in Hong Kong. Water management on stormwater and freshwater has been reviewed across scales, zooming in from infrastructural level to districts and communities. With the unique topographic setting and water quality control in Hong Kong, it takes advantage to increase potable water collection in hillside catchment and maximize stormwater harvesting in urban areas. A new integrated system is proposed to reduce flooding in low-lying urban areas and increase local water supply to develop a greater community resiliency on climate change.

Keywords: freshwater supply; climate resiliency; stormwater management; rainwater harvest; flooding

Enlarge Photo: Despite the projection of more extreme weather conditions, the Hong Kong government has conservative responses towards these future challenges on freshwater supply and stormwater management. By CHAN Ka Yu Phoebe.Enlarge Photo: Local yield is the remaining water source. However, the developing reliance on imported water has wiped out its contribution by prioritizing the use of Dongjiang water in the supply system. By CHAN Ka Yu Phoebe.Enlarge Photo: Brown hatched flood prone areas prove that the current centralized, large scale drainage infrastructures fails to solve local flooding problems and argues for the need of a smaller scale mitigation. By CHAN Ka Yu Phoebe.Enlarge Photo: Almost 90% of rainwater is drained to waste as stormwater. However, the divided water responsibility of DSD and WSD becomes an obstacle to an integrated planning of water resources. By CHAN Ka Yu Phoebe.Enlarge Photo: The regional scale reviews existing freshwater and drainage infrastructure in protected catchment and maximizes the potential of integrative use. Cavern is proposed to be the new form of reservoir. By CHAN Ka Yu Phoebe.Enlarge Photo: This section shows the connection between urban development and hillside protected catchment; and demonstrates how the proposal makes use of caverns, storage tanks for urban catchment, and coastal strategies. By CHAN Ka Yu Phoebe.Enlarge Photo: The community level aims to strengthen local catchment and storage capacities in the built environment. Increasing stormwater collection reduces flooding risks while simultaneously enhancing freshwater availability. By CHAN Ka Yu Phoebe.Enlarge Photo: The proposal aims to increase contribution of local water to the current system, reducing reliance on imported water. Freshwater storage capacity can also capture stormwater to mitigate flooding. By CHAN Ka Yu Phoebe.Enlarge Photo: 3 districts are selected to demonstrate how the multi-scale proposal improves climate resiliency. They focus on different types of development, which set as typology for climate resilient planning in similar districts. By CHAN Ka Yu Phoebe.Enlarge Photo: The perspectives suggest response of different districts upon their urban setting in wet and dry scenario, which water infrastructure caters freshwater, drainage and recreation purpose to the community. By CHAN Ka Yu Phoebe.