Nature-based solutions

for Huế

The GreenCityLabHuế Project aims to provide nature-based solutions (NBS) for the city of Hue to tackle its upcoming challenges such as population and economic growth along with increasing exposure to adverse impacts of climate change. Thereby the project proceeds in three phases: Firstly, during its definition phase (2019-2021) the international project team analyzed expected challenges in the context of climate change, the current status of NBS and green-blue infrastructure (GBI) in the city,  and the socio-economic, legal and political framework for their implementation. Furthermore, first drafts of possible scenarios for the future  development of NBS and GBI were discussed with relevant stakeholders and citizens and sites for preferred future NBS and GBI developments were identified. In the following project phase, the research and development phase (R&D phase starting in April 2021), the scenarios will be evolved and specified, a comprehensive city-wide action plan will be developed and first exemplary interventions will be implemented for testing and illustrative purposes. Lastly, during the project’s implementation phase (starting in 2025), selected proposals out of this action plan will be implemented and put into effect.

The definition phase ended recently. For more detailed information please read our final report of the definition phase.

Background information

Global warming and urbanisation are closely interconnected. Cities are both drivers of global warming and especially affected by its impacts. The need for climate mitigation and adaptation as well as building resilience is therefore becoming essential for urban policy. In this context, nature-based solutions (NBS) in urban and regional planning are gaining increasing importance. NBS refer to the sustainable management and use of nature for tackling environmental and societal challenges such as climate change and the urban heat island effect, water supply security, water and air pollution, food security, human health, and disaster risk management.

The concept of NBS aims at the enhancement and expansion of green-blue infrastructure (GBI), a strategically planned network of natural and semi-natural areas, designed and managed to deliver a wide range of ecosystem services, including green spaces (green) and waters (blue).

Nature-based solutions are designed interventions that are inspired by nature. The properties of plants, soils and other natural elements are used to increase the sustainability and resilience of cities. Thus, bringing more, and more diverse, nature and natural features and processes into cities, through locally adapted, resource-efficient and systemic interventions. Therefore, these solutions span a variety of actions depending on the environmental and societal challenge, the level of intervention and the spatial scale. GBI planning also helps to reduce dependence on ‘grey’ (built) infrastructure that is often more expensive to build and maintain. It is therefore a smart investment for cities, especially in developing countries.

Examples:

The restoring of wetlands and mangroves for the purpose of climate and coastal protection. The de-sealing of soils as well the reduction of the degree of soil sealing help to reduce surface run off following heavy precipitation events due to an increase in on-site infiltration while also increasing the evapotranspiration on site. Solutions like these restore the sustainability of the area and its multifunctionality. New designed and managed artificial ecosystems such as green roofs and vertical green can cool buildings in the summer and prevent heat loss in winter. Infiltration ditches and constructed wetlands which are designed for on-site water infiltration and treatment. Thereby, cooling the surrounding area.

Already today, Hue is effected by impacts of a changing climate. The most obvious are extreme weather events such as Taifuns with heavy rainfall resulting in flooding in the city and the Thua Thien Hue Province and extreme heat waves. In the near future, climate conditions will further change in varying degrees, depending on the models that are used to predict them. During the definition phase of the GreenCityLabHuế Project, current climatic conditions were assessed based on long-term measurements for the 1960 – 1990 period, and future conditions were derived from averaging six downscaled global climate models from the IPCC Fifth Assessment, including (i) Beijing Climate Centre Climate System Model Version 1.1; (ii) Community Climate System Model Version 4; (iii) CNRM-CM5;  (iv) Goddard Institute for Space Studies General Circulation Model; (v) HadGEM2-ES; and (vi) Model for Interdisciplinary Research on Climate.

The images display the future climate conditions under the RCP2.6 (left) and RCP8.5 (right) climate models, expressed as difference to current conditions and averaged at municipal level, for the years 2050 (left) and 2070 (right).

Trends indicate generally warmer conditions and increasing total precipitation for the region:

    • Annual average near-surface air temperature to increase by approximately 1.07°C up to 1.83°C until 2050, and by about 1.11°C up to 2.65°C until 2070
    • Extreme temperatures, proxied by the maximum temperature of the warmest month, to increase by approximately 1.18°C to 2.20°C until 2050, and by 1.24°C to 3.30°C until 2070
    • Annual total precipitation to increase by approximately 38.97mm to 79.33mm (RCP8.5) up to 108.10mm to 141.20mm (RCP2.6) until 2050, and by 74.53mm to 140.41mm (RCP2.6) to 71.92mm to 165.86mm (RCP8.5), respectively

Natural hazards will likely be exacerbated by climate change. This includes increases in heat spells and resulting heat stress as well as flooding. Air quality might be affected simultaneously.

Analysis of status quo of NBS and GBI in Hue

The inventory of GBI presents the distribution of green, blue and open spaces in the city of Hue based on land use data from 2014. The share of GBI in the urban area is as following: forest 6%, agricultural land 19.5%, aquaculture facilities 0.1%, public green spaces 1%, cemeteries 8%, sport facilities 0.4% and waster bodies 10%. Forest and public green spaces not fairly distributed and potential for expansion of NBS can be seen in undeveloped land as well as new and growing urban areas in the Huong So, An Hoa, Thuy Xuan and Huong Long. In addition, potential for the enhancement of NBS can be found in densely populated areas and special zones, e.g. within the citadel.

For more detailed information, please read our status quo report.

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