Urban Grading Planning Method for a More Resilient Lowlands in Ho Chi Minh City and Mekong Delta

Land grading planning is a compulsory step in any urban planning project in Vietnam. Presently, the approach involves determining controlled ground elevations that consider a specific flood frequency related to the urban type, with an additional 0.3 m for residential areas and 0.5 m for industrial zones. However, this method has significant drawbacks, as it necessitates a large volume of fill material and lacks resilience to climate change and rising sea levels. The main issue with the current method lies in the fixed controlled elevation values, attempting to address both surface water drainage and flood prevention simultaneously. In response, this paper suggests a new approach to urban land grading planning, emphasizing the separation of water drainage and flood avoidance tasks. The proposed strategy involves surrounding dams, flap valves, water pump stations, and other elements in conjunction with regularly required controlled elevations to safeguard the area from flooding. The elevations within the dams are selected based on factors such as land conditions, landscape design, and the implementation of a sustainable drainage system (SuDS), incorporating features like vegetated surfaces, pervious pavements, water reservoirs (ponds), and wetland areas. Collected water within the dams can be pumped over the dams to the river or waterfront outside. Importantly, the elevations inside the dams can be much lower than the established controlled elevation values, reducing the need for fill material and enhancing the area's resilience to climate change and rising sea levels.