Flood prevention via sustainable urban drainage systems, Hanoi, Vietnam

by Bui Thi Thuy and Pham Nguyet Anh (TLU), Sam Drabble (WSUP) and Dewi Rimayani Hanoum (UN Habitat)

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Hanoi, the capital city of Vietnam, faces many challenges in wastewater and faecal sludge management which are being intensified by water pollution and urban flooding. The rapid expansion of Hanoi has led to the inadequate management of the city’s wastewater and drainage system, causing damaging and costly floods. In line with the national strategy, Hanoi seeks to be water pollution and flood free by 2030. As a result, much attention has been drawn to wastewater and faecal sludge management.

Sewer pipes in Hanoi are mostly the combined type, collecting both wastewater and stormwater. This system was constructed between 1905 and 1945 during the French colonial period and covered the central part of Hanoi.

This case study details how sustainable urban drainage systems (SUDS) are contributing to urban flood mitigation. In addition, recognizing the potential and potential dangers of wastewater reuse for agriculture, authorities in Hanoi are developing institutional arrangements and policies to protect consumers, whilst enabling farmers to use nutrient-rich wastewater. Wastewater reuse, and its implication at policy level, is another focus of this case study.

Geographic information



City and population:

Hanoi: 8,246,500


  • The rapid expansion of Hanoi, in addition to high rainfall in parts of the city, has led to the inadequate management of the city’s wastewater and drainage system, causing damaging and costly floods. Existing sewer systems are combined, collecting wastewater and stormwater, which has increased the charge on drains in periods of sustained heavy rainfall.
  • Wastewater is commonly reused for agriculture, but guidelines for safe reuse are currently lacking.


  • Extracting lessons learned, Hanoi is focusing on the separation of sewerage and drainage systems for new urban areas to better manage stormwater for flood mitigation.
  • Various stakeholders involved in retention of the water basin (urban lake), wastewater and drainage management have complementary roles and responsibilities for flood prevention.
  • The city of Hanoi designed and is now implementing Sustainable Urban Drainage Systems (SUDS), a Source–Pathway–Receptor approach to manage flooding and reduce pollution risks.