The GreenCityLab

Huế

The GreenCityLabHuế aims to strengthen the climate resilience of the city of Huế through nature-based solutions (NBS), thereby focusing on the development of green and blue infrastructure (GBI) and its effects on impacts of climate change and environmental degradation. In a two years definition phase between 2018 and 2020, the further scope and focus for upcoming activities were defined by the GreenCityLabHuế team with the participation of local decision-makers, experts, stakeholders and representatives of civil society. During its main project phase starting in 2021, the GreenCityLabHuế will generate knowledge, ideas and specific proposals for the future use of nature-based solutions (NBS) and development of green and blue infrastructure (GBI) as measures for making the city and its citizens more resilient against impacts of climate change and environmental degradation. Thereby, the GreenCityLabHuế uses the urban learning lab (ULL) approach by initiating co-learning and co-creation processes to build a common vision for a greener, smarter and more livable urban development in the city of Huế and its surrounding province.

Below you will find background information and insights in the results of activities of the GreenCityLabHuế project. If you want to learn more about nature-based solutions (NBS) and green-blue infrastructure, please click here.

Background

Vietnam is one of the most densely populated countries in the world with a population of about 95 million, living in an area of only 331,221 km2. In addition, with an urbanisation rate of 3.4% per year, Vietnam is undergoing a fast-moving urbanisation process, affecting besides Hanoi and Ho Chi Minh City also secondary cities such as Hai Phong, Da Nang, Can Tho, and Huế. The current share of urban population of over 30% across the nation will grow to a share of over 50% by 2025 (Anh et al. 2013). Moreover, Vietnam is one of the countries hit hardest by climate change impacts (Kreft et al. 2015). Due to its exposed geographical location, Central Vietnam, where the city of Huế (Thừa Thiên Huế Province) is located, suffers regularly from storms, heavy rainfall events and extreme heat waves (UNDP 2008). The outcome of such extreme weather events are often heavy infrastructure damages and casualties (Dang et al. 2016).

The city of Huế is one of the oldest urban areas in Vietnam. The city encompasses an area of about 71 km² and is one of the most densely populated Vietnamese cities with 5,076 person/km². Being the former capital of Vietnam from 1802 to 1945 under the Nguyen Dynasty, Huế City is regarded as the national centre of culture, religion and education. The city has been inherited the cultural values and the magnificent buildings of the Imperial City and other monuments which were collectively recognised as World Cultural Heritage by the United Nations Educational Scientific and Cultural Organisation (UNESCO) since 1993. These sites are: the Huế Citadel (in 1993), the Huế Imperial Music (in 2003), the Nguyen Dynasty woodblocks (in 2010), the Nguyen Dynasty imprints (in 2014), and the Poetry on Huế Imperial Architecture (in 2016).

Huế is located on a narrow plain with a slope from the west to east. The terrain comprises of low eroded hills on deeply weathered sedimentary rocks to the west of the city and depositional plains in the north and east. The historical centre of the city and its surroundings is built on flood plain. The area in the north of the Huong River shows an elevation of 1.8 m to 3.5 m. The elevation in the area south of the Huong River ranges from 2.5 m to flat hills up to 18 m. Areas below two meters are subject to frequent flooding. Situated 100 km south of the city of Huế is the Hai Van pass, a mountain range marking the meteorological divide between the north and south of Vietnam (HCCWG and Tran 2014).

Huế experiences a trend of rural repopulation and urbanization. There is therefore a strong demand for living space in the city. Contrary to the traditional garden houses a trend towards building smaller and higher houses can be observed. No high buildings can be found in the northern part of the city. The economic centre is located in the southern part of Huế City. Due to the high demand in living space available properties are rare. Hence, informal houses and buildings can be found in the city.

Its prominent position as official ‘grade 1 – top priority city’ within the Vietnamese Government’s city rating system and its outstanding historic and educational importance give the city of Huế the status of a role model for the more than 65 other provincial capital cities. The combination of its high exposure to climate change impacts, its relatively young and well-educated population, and its touristic importance make Huế an ideal location for an Urban Learning Lab (ULL) for innovative, participatory and thus suitable concepts of green-blue infrastructure (GBI) and urban climate change mitigation and adaptation.

Literature

Anh, T. T., Phong, T. V. G., Tuan, T. H., & Mulenga, M. (2013): Community consultation for long-term climate-resilient housing in Vietnamese cities: a comparative case study between Hue and Da Nang. Asian Cities Climate Resilience, IIED.

Asian Development Bank (ADB) (2015): Hue GrEEEn City Action Plan: Main report. Online: https://www.adb.org/sites/default/files/publication/179170/hue-greeen-city-ap.pdf.

Dang, T. N., Seposo, X. T., Duc, N. H. C., Thang, T. B., An, D. D., Hang, L. T. M., & Honda, Y. (2016): Characterizing the relationship between temperature and mortality in tropical and subtropical cities: a distributed lag non-linear model analysis in Hue, Viet Nam, 2009–2013. Global health action, 9(1), 28738.

Kreft, S., Eckstein, D., Junghans, L., Kerestan, C. and Hagen, U. (2015): Global Climate Risk Index 2015. Who Suffers Most From Extreme Weather Events? Briefing Paper. Germanwatch 2015.

UNDP (2008): Climate Change and Human Development in Vietnam, UNDP Human Development report 2007/2008. Online: http://hdr.undp.org/sites/default/files/chaudhry_peter_and_ruysschaert_greet.pdf.

Climate Change

The city of Huế is located in the transitional climate zone, featuring characteristics of a tropical humid monsoon climate. In summer months the average temperature is 29°C to 30°C, with extreme temperature peaks of 38°C to 41°C during June and July. The dry season is from May to September with dry air from southwest winds8T. In the winter months average temperature ranges between 20°C and 23°C. The rainy season from October to April is influenced by northeast monsoons, causing considerable rainfall (HCCWG and Tran 2014; Fick and Hijmans 2017). Precipitation rates of Huế are amongst the highest in Vietnam. Therefore, Thừa Thiên-Huế province is considered to be the most prone to flooding in Vietnam. Precipitation distribution is unequal across the months and is mainly concentrated in the rainy season, especially during October and November with over 30 % of annual precipitation.

Already today, Huế 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 Thừa Thiên Huế 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 Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment.

The IPCC typically uses four scenarios to predict possible future climate conditions based on possible future pathways of the greenhouse gas concentration in the atmosphere, the so called “Representative Concentration Pathways (RCP)”. All four pathways rely on different future volumes of greenhouse gases depending on upcoming emissions, whereby the scenario RCP 2.6 assumes the lowest possible amount of emissions and the scenario RCP 8.5 assumes the highest, unfortunately more probable, amount of future greenhouse gas emissions.

The images display the future climate conditions in Huế under the two scenarios RCP2.6 and the RCP8.5 climate models, expressed as difference to current conditions and averaged at municipal level, for the years 2050 (left) and 2070 (right). You can change the displayed scenario by moving the green button with your mouse to the left for RCP8.5 or to the right for RCP2.6.

The observed trends for future climate conditions in Huế indicate generally warmer air temperatures and increasing rainfall (total precipitation) for the already today tropical-humid region. Details are listed below:

  • Annual average near-surface air temperature is predicted 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.

The image shows the Thừa Thiên Huế Province and indicates probable future changes due to climate change for different parts of the province for the RCP2.6 and the RCP8.5 scenarios.

Status quo

With about 12.9 m²/person, the green space per capita is comparatively high in Huế. However, green (and blue) spaces are not equally distributed across the city – with access to green areas being particularly limited in the historical centre of the city – giving rise to the implementation of new GBI elements. Huế is known as the “Garden City” and well-known for its typical garden houses, which contribute to a large amount of green space in the city. Those are located mostly in the wards of Kim Long, Thuan Thanh, Thuan Hoa and Tay Loc. About 4,228 garden houses with a size of at least 400 m² are located in Huế. The Huế garden houses are characterised by a large number of plantations (50 species per house), which create a high tree density and a corresponding ecosystem. Although the garden houses are considered a unique feature of the city, they are still faced with a loss in size and architecture due to economic motives, changes in function and modernisation trends. Due to the increase in residential areas with modern architecture, these structures with the natural features of vegetation and water are lost. The same applies to green areas integrated in the layout of properties of French colonial buildings.

The largest river system in Thừa Thiên Huế province is the Huong River system. It consists of the the Huong River and its three tributaries – the Bo, Ta Trach and Huu Trach. Its main course is 104 km long with a basin covering an area of 2,830 km², which is 56 % of the area of the province (HCCWG and Tran 2014). The highest density of blue infrastructure elements is located around the Citadel with a system of up to 48 lakes, ponds and the 3 km long canal of Ngu Ha with the total size of 810,420 m².

Inventory of Green and Blue Infrastructure

The status quo of green and blue infrastructure (GBI) development in the city was analyzed considering the current distribution of natural and semi-natural green (vegetation covered) and blue (water covered) spaces within the city and its surroundings. The inventory of GBI presents the distribution of green, blue and open spaces in the city of Huế based on land use data from 2014. Although land use data form the basis of the inventory, it is actually a combination of land use and land cover. Nevertheless, the map provides a good overview of the distribution and share of GBI in the city of Huế.

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.

Scenarios

For the creation of visions for future sustainable urban developments based on nature-based solutions (NBS) and green-blue infrastructure (GBI), the development of possible future scenarios is key. Scenarios help to visualize future developments, and to understand and assess their possible impacts. An important component for creating scenarios of future urban developments is the involvement of local stakeholders, including decision-makers, experts and representatives of civil society. Stakeholders are extremely valuable for providing a first estimation of which measures of land management will be positively perceived by the public, making their successful implementation more likely and effective. Therefore, the GreenCityLabHuế uses a participatory co-creating modelling approach for the development of possible future scenarios. Knowledge generated through a first status quo analysis and the inputs from local stakeholders was used to envision ideas of level, intensity and placement for the future urban developments in the city regarding green space saving, development or enhancement. The thereby outlined visions function as thematic storylines, so called narratives, of desired future urban developments. Based on these, land use change scenarios will be modeled using a multi-layer geographical information system (GIS) model. This enables the simulation and evaluation of possible impacts of specific land use changes regarding their benefits for climate adaptation and enhancement of ecosystem services and thus for the improvement of the quality of life of the citizens of Huế.

In 2020, the GreenCityLabHuế started the scenario development process with a stakeholder workshop, where local experts discussed possible future urban developments regarding green and blue infrastructure. Based on their inputs and ideas, narratives that describe possible and desired future green and blue infrastructure (GBI) developments that are adopted to the specific characteristics and local conditions of the city of Huế were created. Based on these narratives the scenarios will be specified and their impacts will be assessed. Finally, they will result in a comprehensive city-wide vision that will make concrete proposals for the implementation of green and blue infrastructure interventions that contribute to making Huế more resilient against future environmental challenges.

Based on proposals for optional scenarios, Huế-specific narratives for each scenario were formulated in a common co-creation process by researchers and stakeholders during the stakeholder workshop. They can be seen in the following image. These narratives will be the basis for subsequent steps of green and blue infrastructure planning within the framework of the GreenCityLabHuế.

Below you will find the narratives of each scenario with the original narrative proposed by the scientists on the left and the Huế-specific narratives adopted by the stakeholders on the right.

Scenario A
Business–as-usual
Business–as-usual
City growth and expansion result in continuous encroachment into natural and agricultural land that is converted into built-up land and few urban green spaces. No measures will be taken within the existing infrastructures.
In comparison to the 2030 planning, no additional measures will be taken. The business-as-usual scenario is characterized by the 2030 green space planning. Planned green spaces include those in the citadel, where military land-uses are converted to urban green spaces. No particular interventions or actions are foreseen in other existing or planned land-uses.
Scenario B
Small-scale improvements
Small-scale improvements through traditional green elements
City growth and expansion result in continuous encroachment into natural and agricultural land. However, to improve the sojourn quality and as aesthetical intervention, trees are being planted in the newly built-up areas. Still, only few green spaces are created. Within the inner city and the citadel, additional trees are planted to improve air quality.
This scenario improves on the business-as-usual scenario through the implementation of additional actions/interventions. Actions will be taken in both existing and planned land-uses (across all relevant types of areas). Mostly, smaller-scale (selective and small-footprint) GBI elements/actions will be considered that are deemed traditional/popular, and that are therefore also (very) feasible for implementation. These GBI elements/actions include the planting of (street) trees, shrubs and hedges, the creation of tree alleys, the construction of green playgrounds and the greening/improvement of existing playgrounds, or the construction of small parks/pocket parks. Selective actions in existing land-uses include the greening of balconies and the construction of vegetated pergolas.
Scenario C
Larger-scale improvements
Moderate to large-scale improvements
Encroachment into natural areas will be limited. Instead, most of the expansion of Hue is accommodated by agricultural areas. The new built-up land will be greened by planting of trees, intensive greening of, e.g., courtyards, and rain gardens. Within these newly constructed areas, more green space per capita will be created in the form of woody public green spaces. Several measures are applied across the city of Hue for the improvement of existing infrastructures, e.g., greening by the planting of trees, intensive and extensive greening of courtyards, or the addition of green verges. Existing green spaces will be improved in quality, e.g., by the implementation of playgrounds. These measures should help adapting the city to future extreme conditions (heat, flooding) and improve public health, e.g., by tackling air pollution.
This scenario improves on the small-scale interventions in scenario B through considering GBI elements/actions with larger spatial footprints (moderate- and large-footprint actions), as well as less traditional/not yet popular GBI elements. In existing land-uses, selective actions similar to B are anticipated; however, in addition to scenario B, also green courtyards, ponds, and house gardens will be considered, and community gardens will be proposed as well. Green spaces shall be improved, e.g., through the planting of trees, shrubs, or hedges, e.g., to construct woody playgrounds. Existing infrastructures may be improved further through permeable pavements, bioswales and green verges, especially in renovation and redevelopment areas. Newly constructed areas, represented by planned land-uses within in-fill areas, redevelopment areas and new development areas, provide the opportunity to implement GBI elements/actions with moderate and/or large spatial footprints, including, e.g., neighborhood green spaces, riverbank green, medium-sized and/or large urban parks, orchards, green sports facilities, historical gardens, and meadows. It is anticipated that the 2030 urban planning may be revised if needed to spatially accommodate such larger-footprint actions. In so doing, the implementation of such actions/GBI elements, the green space per capita in planned land-uses shall be increased in comparison to the business-as-usual, or the smaller-scale improvements proposed in scenario B.
Scenario D
Biophilic city
Eco-city
Natural areas will be protected. As an additional climate change mitigation measure, forest areas will be increased by afforestation. Spatial expansion of the city will be accommodated only through the conversion of agricultural areas and undeveloped land into built-up land. Through the application of building codes for newly constructed buildings to enable the greening of roofs and facades, as well as the high share of (woody) public green areas, these newly constructed areas will be of very high environmental quality. Similarly, existing infrastructures will be improved, e.g., by planting of trees, intensive and extensive greening, adding green verges, retention basins and bioswales. Public green spaces will be greened by adding of trees and woody elements. Their quality is additionally increased by the implementation of playgrounds. These measures shall improve the resilience of Hue against future climate conditions, improve public health and well-being, and drastically improve sojourn quality and recreative potential across the city.
The biophilic city narrative builds upon narrative C, and assumes that the green space per capita ratio shall be increased further. In addition to narrative C, it is proposed that urban forests and/or orchards may be planted, or large urban parks and (historical) gardens be constructed withinland reserved for future development. Moreover, additional property-related selective actions are proposed, including green roofs, façade-bound green walls, and/or blue roofs. These actions should be implemented may be implemented where feasible within existing land-uses, and particularly in planned land-uses, their implementation may be increasingly accommodated through the adaptation of building.
Site Selection

The GreenCityLabHuế aims at providing proposals for the implementation of future interventions of green and blue infrastructure. Within the scenario development and modelling process, potential effects of specific interventions on different types of ecosystem services will be assessed. Thereby, effects of green and blue infrastructures on ecosystem services will be simulated and investigated on different spatial levels. There will be an assessment on the scale of the whole city and on the scale of smaller parts of the city for certain city districts and wards. While the city scale simulation of effects allows a more general overview, the ward scale modelling can portray the impacts of specific green and blue infrastructure interventions more detailed on a smaller scale. Furthermore, the GreenCityLabHuế aims at demonstrating and evaluating effects of green and blue infrastructure in practice by implementing experimental green and blue infrastructure interventions on the scale of individual lots, so called “showcases”. On the one hand, these showcases will increase the visibility of the GreenCityLabHuế activities in the city and will serve as descriptive practical examples that enable decision-makers, stakeholders and citizens to learn more on nature-based solutions and the effects of green and blue infrastructure. On the other hand, they will be used as “real life laboratories” for validating and measuring the modelled impacts on ecosystem services. During the project’s definition phase, the wards where the small-scale modelling will be applied and where the showcases will be implemented were selected in a participative process with local stakeholders from Huế. If you want to learn more on the selected sites, please click here.

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