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CANTHO: Ecological Structures to Guide Urbanization (2010-13)
Location: Cantho, Vietnam
Designers: RUA, WIT Architecten, LATITUDE in collaboration with SIUP Kelly Shannon, Bruno De Meulder, Guido Geenen, Cati Vilquin, Phebe Dudek, Daan Derden, Annelies De Nijs, Remi Van Durme.
Commissioned by: Cantho People’s Committeei
Area: 140,200 hectaresa
Period of Design: January-September 2010
VIETNAM
Historical Transformation of Cantho’s Landscape
Cantho (population 1.2 million) is located in the heart of the enormous floodplain of the Mekong Delta, at the confluence of the Hau (lower branch of the Mekong) and Cantho Rivers. The French colonial enterprise in Indochina (1876-1954) radically transformed the Mekong Delta’s watery landscape into a highly productive, irrigated territory known as Vietnam’s ‘rice basket’.
Cantho is the delta’s most important and rapidly urbanizing city (primarily due to urban-rural migration) and the predicted effects of climate change are daunting, while its modernization process includes the development of road-based urbanism and new engineering methods to regulate the hydraulic landscape. Accessibility and connectivity afforded by the new roads – including the recently opened Hau River Bridge – have radically enhanced its strategic location.
Cantho, heart of the Mekong Delta
Situated on the confluence of rivers and in the centre of the 'rice basket' of Vietnam, Cantho nowadays is undergoing drastic consequences of climate change and rapid urbanization.
Challenges of Urban Expansion and Environmental Impact
Cantho’s expanding hybrid territories have spatial limitations due to the intermingling of built-up environments and agricultural land, which increases the conflicting claims on the territory (urban functions versus natural or controlled floodplains, location of wastewater treatment infrastructure, water management functions versus ecological purposes). One of Cantho’s largest threats is the loss of absorptive low lands, which are inadvertently filled (with up to 2 meters of soil) to support urbanization. The absorptive capacity of the land is diminished as the amount of paved areas increase – with side effects of faster rainfall run-off and a lowering of the natural groundwater table.
Indigenous Water-based Identity and Minimal Topographies
Cantho's territory is characterized by a colonization of the marshlands for production and the clustering into market towns. The waterways were vital for both systems, and remain so until today. At the same time, the deltaic geography results in minimal topographies that become extremely important as they indicate the differences between safe and unsafe land.
Organized dispersal
The proposed development scheme for Cantho envisions an alternative linearity along the Hau River. Instead of a continuous built-up strip along the river, there is the possibility of new interplays of landscape, infrastructure, and urbanization to create a series of differentiated centralities. The proposed trajectory of the highway parallel to the Hau River is retraced to safeguard the mesh of orchards southwest of the city center. Similarly, the upstream landscape along the Hau River is protected as a complement for the new administrative center of Omon, which is set back from the river and more linked to the new highway.
Green-Blue Structure Frame of Urbanization
A soft engineering base of green-blue structure offers a strong frame for the flexible and long-term development of the city. The green network is primarily composed of the orchards in the south, the regional-scale Hau River hi-tech agricultural park, the 50+km Cantho Linear Park (hosting recreation) and the tree-planting program of the 'civic spine'. Topographical levels and soil conditions allow the definition of a wide variety of tree specimens. The blue network is designed to addresses both water quantity (flooding, storm water retention, drainage and irrigation) and water quality (sewage, purification) which are then realized by a rigorous enforcement of the cut and fill balance principle during the process of urbanization.
Water Management and Flood Risks
Water quantity problems are mainly related to hydrological extremes: high flow discharges and flood risks along rivers and urban drainage systems, and low flow discharges along rivers. Ultimately, the balance between hydraulic, ecological, agricultural, and urban (housing, industry, recreation) uses of space is far from optimal.
As well, Cantho’s entire drainage and sewerage system (often un-hygienically mixed) is over-stressed and its integrity jeopardized. Encroachment of water bodies alters ecologies and inevitably affects the severity and frequency of flooding, not to mention an increase in environmental degradation and pollution.
Reappearance of the Parkway: a Civic Spine Embedding Public Transport & Equipments
A high-land 'civic spine' constructs a new public armature to operate at the city-wide scale. In the 50km+ armature of vast dimensions is embedded a transport boulevard - with a reserve of land for an envisioned light-rail system storm-water systems and public equipment. The armature is systematically planted with trees, connects to elevated urban platforms with public programs (including administration buildings, hospitals, universities) as well commercial and office spaces. In this sense, the civic spine adapts the classic figure of the parkway to Vietnam's future conditions.
Urban Platforms Rationalize and Modernize Cantho's Urban Fabrics
Precise topographical manipulation is used as a primary design tool to guide urbanization and steer tree plantation. Retaining a 'cut-and-fill' balance is fundamental. New urbanization is to be built on high-land platforms in both the rural and urban areas of Cantho. The platforms are developed as various heights of fill (from 2.7 meters upwards) and correspond to desired levels of safety (from flooding). Their geometry is partially informed by the pre-existing conditions of the landscape, while simultaneously accommodating and shaping tissues that rationalize and modernize Vietnam's building traditions.
Soft Engineering Approaches for a Resilient Cantho
Soft engineering approaches are proposed in order to develop Cantho as a resilient and adaptable city. A structural interweaving of hydrology, soil conditions, and a new urban morphology works with the creation of a manipulated topography that rearticulates the existing logics of the territory. The delta’s agricultural territory is basically generated through the inscription of canal systems – pre-colonial and French – in the natural water structures that interact as warp-and-woof.
The master plan revision constructs Cantho’s future urban structure on similar lines: interweaving a green-blue structure and an urban structure. The green-blue structure defines the counter-figure for ‘urban platforms’ (on raised artificial land) as the backbone of the city that inscribes itself to a large extent into the natural water structure and soil conditions.
A ‘soft engineering’ approach is addressed as a way to work with the forces of nature, in order to reduce or mitigate the likely impacts of today’s increase in natural disasters, while the revised development of the city will be guided by new interplays of landscape, infrastructure, and urbanization.
Cantho Revised Masterplan 2030
The OSA/ RUA/ WIT/ LATITUDE proposed revision of the Cantho masterplan developed context-responsive ecological structures to guide urbanization and weave an additional layer of warp-and-woof into the landscape.
Cantho Revised Masterplans by SIUP
The revised masterplan's biggest move is to keep the exising orchard structure and to move the new administrative city of Omon away from the Hau River, creating a large riverfront park and thus avoiding the development of a continuous linear city along the lower branch of the Hau River.
