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Greening the gap Landscape-based stormwater solutions supporting the social life of Ho Chi Minh City, Vietnam

Greening the gap

Landscape-based stormwater solutions supporting the social life of Ho Chi Minh City, Vietnam 30 ECTS points Master Thesis in Landscape Architecture Department of Geoscience and Natuaral Resource Management Faculty of Science University of Copenhagen Pernille Vad NĂ¸rmark, lpj926 Supervisor: Marina Bergen Jensen May 2019

Pernille Vad NĂ¸rmark

Ack nowl e d g me n ts

I would like to express my gratitude for all the people who contributed to the completion of this thesis. Without all of your help, this project would not have been possible. I would like to thank Sweco for giving me the opportunity to work with them on a project dealing with the consequences of climate change in Ho Chi Minh City, Vietnam. A special thank you to Project Director Martin Vilhelmsen for including me in the project, connecting me with local employees and guidance the first week of my fieldwork. Mrs. Hai, Mr. Lam and Ms. Van Anh Bui for introducing me to local organizations, translating conversations with locals and helping me reach my goal for the fieldwork and Mr. Binh for providing me with all the necessary data. My supervisor Marina Bergen Jensen, for her knowledge, constructive feedback and guidance. Rikke Hedegaard Jeppesen and Marie Lene Aalund Balle for professional feedback on my design. Erin Hauer for your unique feedback and our interesting discussions on Landscape Architecture in general and in developing countries. Ditte Godske Jensen for proof-reading and commenting on the report. A special thanks go out to every local Vietnamese who took the time to answer all of my questions and for showing interest in my project.

Tóm tắt

Luận văn này nghiên cứu cơ hội thực hiện giải pháp thoát nước mặt bằng hạ tầng cảnh quan tại các khu vực dân cư xây dựng đông đúc ở TP.HCM thông qua phương pháp tiếp cận thích ứng dựa vào cộng đồng. Mục tiêu của luận văn là nhận diện, đề xuất một giải pháp thay thế cho hệ thống tuyến cống thoát nước truyền thống nhằm giảm thiểu rủi ro ngập nước của TP.HCM, cải thiện khả năng dân sinh cũng như hỗ trợ cuộc sống xã hội của Thành phố.

Trong những năm qua, quá trình phát triển đô thị hóa đang diễn ra với tốc độ nhanh đã biến TP.HCM trở thành siêu đô thị đầu tiên ở Việt Nam với mốc dân số đạt 10 triệu người. Quá trình đô thị hóa này đang biến các khu đất trũng có khả năng thấm nước thành các bề mặt bị bê tông hóa, dẫn đến nguy cơ bị ảnh hưởng bởi mực nước biển dâng và ngập nước. Luận văn đề xuất ba giải pháp thoát nước mặt bằng hạ tầng cảnh quan đa chức năng và theo bối cảnh cụ thể. Qua các cuộc phỏng vấn với người dân địa phương, chúng tôi đã nhận diện được những mong ước và nhu cầu của họ về một đô thị đáng sống hơn. Thiết kế nội dung tập trung vào giải pháp giảm thiểu rủi ro ngập nước, hỗ trợ và cải thiện đời sống xã hội của TP.HCM.

Về mặt lịch sử, Việt Nam nói chung và TP.HCM nói riêng là một quốc gia “phương Tây hóa” và chịu ảnh hưởng lớn bởi người Pháp trong thời gian thuộc địa và người Mỹ trong giai đoạn chiến tranh Việt Nam. Lịch sử của Thành phố cũng đã làm ảnh hưởng nhiều đến các chuẩn mực hành vi, đặc biệt là lối sống sinh hoạt thoải mái ở không gian công cộng là điểm rất đặc trưng ở TP.HCM.

Abs tract

This thesis investigates the opportunities for implementing a landscape-based stormwater solution in the dense built-up environment in Ho Chi Minh City, through a community-based adaptation approach. The aim of the thesis is to visualize an alternative solution to a conventional engineered sewer system to mitigate the flood risks in Ho Chi Minh City, enhance the livability and support the social life of the city.

In the recent years, rapid urbanization has turned Ho Chi Minh City into Vietnamâ&#x20AC;&#x2122;s first mega city, reaching the benchmark of 10 million inhabitants. The rapid urbanization is transforming low-lying permeable land, into impermeable surfaces making the city vulnerable to sea level rise and flooding. The report proposes three contextual multi-functional landscape-based stormwater solutions. Through informal interviews with locals, the wishes and needs for a more livable city unfolded. The design focus on mitigating the flood risk and support and enhance the social life of Ho Chi Minh City.

Vietnam and Ho Chi Minh City was historically a westernized country and was influenced by the French during the colonial times and USA during the Vietnam war. The history of the city has influenced the praxeological norms, in particular the liberal approach to the use of public space is unique for Ho Chi Minh City.

Contents

Prologue & motivation Abbreveations Research question Delimitations Method

5 7 8 8 9

An introduction

12 13 15 17 19 21

A city of waterways

24 25 27 29 31

The social green city

34 35 37 39

A case study

42 43 45 47 49 51 53

Vietnam Climate The history of Ho Chi Minh City Ho Chi Minh City today Aerial map of Ho Chi Minh City

Rivers & canals Water resources in the Ho Chi Minh City Region Solid waste Climate change & its impacts on Ho Chi Minh City

The urban structures & landuse The green city Life of the streets - the social sidewalks

Spatiality & green infrastructure The long list - Case studies Site I Site II Site III Challenges & strengths

The selected case area

56 57 61 63

The design

The design The design - Concept for the Swale, Evaporation The design - Concept for the Trench, Multi-functional The design - Concept for the Rill, Conveyance The design - Canals, detention The design - Under overpasses, detention The values of landscape-based stormwater solutions

66 67 69 75 81 87 88 89

Discussion & reflections Conclusion References

91 92 93

Site II - The case area Street typologies The needs & wishes from the locals

Prologue & mo tiv a tio n

For the past two years, the main focus in my projects has been sustainability and stormwater management. After taking an elective course in tropical botany, I was intrigued by the many possibilities within tropical botany in terms of landscape architecture and designing resilient cities.

is an upgrade of the sewer system, because of the crucial consequences climate change has on Ho Chi Minh City. I started thinking of alternative ways to mitigate the flood risk and enhance the social life of an urban area in Ho Chi Minh City. Diving into the project it quickly became clear to me that the people of Ho Chi Minh City had to play an important role for the design.

I started looking into different developing countries in the tropical climate zone, where the opportunities to create resilient urban areas and enhance livability seemed endless. In the fall of 2018, I was offered the opportunity to work together with Project Director Martin Vilhelmsen, who was directing a project in Ho Chi Minh City, Vietnam. The project

This project is a result of my professional aspirations to create inclusive livable resilient urban spaces for all people, all cultures and greening our cities.

The Nheu Loc-Thi Nghe Canal after it has been greened and cleaned, inviting people to sit down under the many trees

Abbrev ia tio n s

HCMC Dist. AMSL UHI SLR

Ho Chi Minh City District Above Mean Sea Level Urban Heat Island Sea Level Rise

Res earc h q u e s tio n

How can a patchwork of landscape-based stormwater solutions be implemented in the dense built-up environment in Ho Chi Minh City with a community-based adaptation approach and serve as multi-functional spaces and mitigate the flood risk?

Delimitat io n s

This thesis focus on the morphology and praxeology, specifically within three sites in district 4 and 8 in Ho Chi Minh City. The proposal is based on field observations, gathered through a spatial analyzis in a specific site.

because the calculation that are needed is outside the field of landscape architecture, and would require assistant from an engineer. The design is a contextual landscape-based stormwater solution. The design is based on wishes and needs from locals in specific area, but the design is adaptable solutions that can be modified and implemented in other cities dealing with the samme challenges, specifically in a tropical clamate.

Many clogged sewer inlets were observed during the field work, assuming there is a pressing need for an upgraded sewer system in Ho Chi Minh City, and it is expected that the surface run-off would mix with the wastewater from the sewage system. The design solution works with stormwater and does not deal with black water and contamination of the existing canals. Furthermore, it is not a fixed solution managing a specific amount of stormwater,

The design proposal is a contribution to visualizing a landscape-based stormwater management approach in a developing country.

Method

To find out how landscape-based stormwater solutions can be implemented in the dense built-up environment in Ho Chi Minh city, with a community-based adaptation approach, a case study, using different disciplines within the field of landscape architecture was performed. Furthermore, a literature study was done, to supplement the case study.

I chose three case areas within an area that Sweco had already conducted surveys and data was accessible to me. A litterateur review is used to understand Vietnamâ&#x20AC;&#x2122;s history, natural habitats and Ho Chi Minh City in terms of current situation and challenges, and the future impacts of rapid urbanization and climate change. Furthermore, a review of maps and collected data from surveys conducted by Swecoâ&#x20AC;&#x2122;s team in Ho Chi Minh City, has contributed to a greater understanding of the morphology of the urban fabric.

This thesis is a collaboration between the writer and the consulting engineering firm Sweco. Together with Sweco Ho Chi Minh City was selected as my case area. Ho Chi Minh City is ranked as one of the top five cities in the world, in terms of the civil society being largely exposed to flooding. Furthermore, the city is facing other major challenges, including subsiding land caused by groundwater extraction, intensified typhoons during the wet season and reaching the benchmark of 10 million inhabitants, making Ho Chi Minh City Vietnamâ&#x20AC;&#x2122;s first mega city. The rapid urbanization is transforming permeable surfaces and natural retention and evaporation areas into impermeable surfaces increasing the surface runoff. Part of the new urban fabric is developed in the southern part of Ho Chi Minh City, which is a low-lying area between 0-2 m above mean sea level, thus this area is extremely sensitive to sea level rise. The increased risk of typhoons makes the overall situation critical.

As part of the case study, I visited Ho Chi Minh City for four weeks to conduct field work. This included field observations, documented with a video camera, photography, sketching and writing. The screening of the selected case areas was verified by the field observation. The case study was inspired by patch-corridor-matrix model used in landscape ecology, specifically investigating the urban patches including, parks, green patches, greenery along waterfronts, community gardens and vacant lots, within the case areas. The model was used to make a structured and comparative analysis of the three sites. The result of the case study was a selection of one case site. The selected case site met most of the criteria on the long list. This site also represented three different street typologies observed other areas in Ho Chi Minh City. Hence the results can to some extend be implemented in various different neighborhoods in Ho Chi Minh City. The design solution is an adaptable solution, making it easy to modify and implement in other cities facing some of the same challenges.

Before traveling to Ho Chi Minh City, I used Google Earth, Google Maps and map data provided by Sweco, as screening tools, to get an understanding of the city. Based on the screening and to find out how landscape-based stormwater solution can be implemented in a dense built-up environment, I sat up a list of criteria (a long list). Based on the long list

In order to get a spatial understanding of the case site, a spatial analysis was conducted focusing on the morphology of the area, documented through photography and sketching. With the help of a local Sweco employee, I was able to have small informal interviews with some of the local residents during the site visit. This gave a unique insight to the wishes and needs in terms of safe livable spaces in the dense urban fabric, without compromising the livelihoods of the locals. In addition to the morphological analysis the praxeology of the social conduct in the streets, were studied throughout the field trip, and was not limited to the case area.

Using the landscape architecture method of sketching and photography, possible street designs for stormwater management, based on detention, conveyance and evaporation combined with assessing site conditions and localâ&#x20AC;&#x2122;s needs and wishes, suitable solutions were gradually reached. This approach corresponds to the hermeneutical spiral, were a result is reached through an iterative process of sketching see fig. 1.

Sketching Understanding Sketching Understanding Sketching Understanding

Sketching Understanding

A local Sweco employee, Mr. Lam taking a break between informal interviews with locals

Fig. 1 Spiral inspired by the hermeneutical circle, used to gradually reach a design solution

An i n tr o d u c ti o n introducing Vietnam & Ho Chi Minh City

Vietnam

This passage is an introduction to Vietnam and HCMC, to provide an understanding of the case area and the context. Vietnam, officially known as The Socialist Republic of Vietnam (Sterling et al. 2006) is located in South East Asia bordering Laos and Cambodia to the west, China to the north and the South China Sea to the east and south. In 2017 the total population in Vietnam was 95,540,800 with 65.8% living rural areas (The World Bank 2019). A rich biodiversity Vietnam is home to many different habitats includinghighland cloud-forests, red coastal sand dunes, savannah like grass lands and deltas. It is a country with rich biodiversity and some of the species are endemic to the region and those adjacent. Ethnic diversity But it is not only the natural habitats that are rich in diversity, 54 ethnic groups have been recognized in Vietnam (Sterling et al. 2006) the biggest group is the Viet also known as Kinh, making up for 85% of the population in Vietnam (Sterling et al. 2006). The

Coastland

Rural farmland

54 ethnic groups are spread over the country, still practicing various traditional rituals and festivals (Sterling et al. 2006). Different Asian ethnic groups particularly the Chinese, influenced Vietnamâ&#x20AC;&#x2122;s early history. Westerners started appearing in the region in the early 1600s specificaly Portuguese and French missionaries and traders started appearing (Kim 2015). French colonial time and U.S. settlement In 1859 the French invaded Vietnam and in 1861 the French captured and destroyed the Vietnamese citadel and Saigon (historic name for HCMC) became the capital of South Vietnam (Kim 2015). The French colonial period lasted until the 1954 Geneva Convention. During the 1950s the tension between North and South Vietnam rose, and with the US-backing South Vietnam with free-market capitalism, this became the start of the Vietnam war between North and South Vietnam and America, with US-military presence in Vietnam from 1954 to 1973 followed by post-revolutionary years from 1976 to 1985 (Kim 2015).

Mega city

Rich biodiversity

Highlands

Rich biodiversity

Ho Chi Minh City

Cl imate

Like most of South East Asia, Vietnam’s climate is associated with monsoons (Sterling et al. 2006). The climate in the HCMC region is a typical tropical wet and dry climate (Katzschner et al. 2016). The dynamic of the monsoon, produces two seasons. The dry winter last from mid-November to the end of march. April and may are transitional months into the wet summer monsoon season, with heavy rains that last until October-November (Sterling et al. 2006).

The average temperature in the HCMC region is 2728 ºC but can reach as high as 40 ºC (Katzschner et al. 2016). Due to climate change these temperatures are constantly increasing. Another factor that should be taken into account is the Urban Heat Island effect (UHI), that influences the temperatures in urban areas with up to 10 ºC, compared to adjacent rural areas. This effect on temperatures is expected to rise, because of the rapid urbanization and economic growth, two factors that are defining for the development of HCMC (Katzschner et al. 2016)

The annual average precipitation in Vietnam is between 1400-2400 mm (Katzschner et al. 2016).

Dry season

UHI effect

Wet season

A local street vendor setting up a sunshade on a steet with only impermeable surfaces that reflects the heat from the sun

The his to r y o f Ho Ch i Mi nh C i t y

A young city HCMC is a fairly young city, around 300 years old. The beginning of the city we know today started with people settling around the Mekong delta in the 1600s. The area was then called Prei Nokor, but in the 1600s when the area was fairly occupied, it was given the name Sai Gon.

Westernization When the city Saigon was invaded by the French in 1859, it became part of the French colony together with Cambodia and Laos (Kim 2015). The colonial time lasted until 1954 and during this time, the French made several masterplans for the city, turning it into a modern city. You can still see remains of French architecture around the city today. As a result of the westernization HCMC has historically had a more liberal norm when it came to public spaces, with very few regulations compared to Hanoi in the north that has been more influenced by the chineese. Throughout the French colonial times, Chinese people moved to the city of Cholon just west of Saigon (Kim 2015).

The importance of water The people found many advantages to settling around the delta because of the location close to the South Chinese Sea, and the many water ways that could be used for trading and most of the economy was based on export. In 1698, the rulers at the time (the Nguyen Lords) occupied 1000 km2 of the land, is recognized by local historians, as the beginning of the city.

After the French had ruled for almost a century the French military was replaced by the US army in 1954. Vietnam was now divided into North and South Vietnam. The north was very much influenced by communist China and the Republic of South Vietnam was influenced by capitalism of the U.S. The capital of the Republic of South Vietnam

Cholon - The China Town of Saigon In the late 1700s, the city mostly consisted of small huts along the river banks. East of the city Saigon the smaller area named Cholon, was recognized as a different city. In the late 1700s most of the inhabitants of Cholon were Chinese, some of them forced to live there after a bloody massacre in Saigon.

Farmland

Liberal approach to public spaces

City constructed along the canals

was Saigon and was the military headquarter for the US army. Between 1960 and 1970 around 1 million people migrated from the rural areas to flee from the war and moved to Saigon, many of them settled in informal slums along the riverbanks. Despite attempts to solve that problem via many different masterplans for Saigon it failed to improve the living standards because of the war (Nguyen et al. 2015).

In 1975 the civil war ended, and Vietnam was reunited into what we know today as the Social Republic of Vietnam. The capital was now Hanoi in the north and in 1976 the city Saigon changed the name to Ho Chi Minh City in honor of the president of the Vietnamese revolution (Nguyen et al. 2015).

Historic map of Ho Chi Minh City from 1895, showing the urban development around the rivers and canals Image source: https://saigoneer.com/saigon-infrastructure/2400-these-11-wonderful-old-maps-show-the-evolution-of-saigon-and-cho-lon

Ho Chi Min h City to d a y

A well connected economic hub HCMC is the biggest city and economic hub in Vietnam. With its location and infrastructure, roads, airport and harbor, it is well connected both domestically and internationally. The city is located on the northern fringe of the Mekong Delta and downstream of Saigon River and rivers and canals have always been a crucial element for the city. This city is mostly built on old marshland, with a flat terrain. That combined with the many waterways, makes the city very sensitive to flooding.

It is predicted that the population will grow 3.5% every year (Schwartze 2016), this means that by 2025 the population in the urban core will reach more than 10 million people and the HCMC region 25 million people (Schwartze 2016). A shift in the economy One of the main reasons for this rapid urbanization is migration. Vietnam is transitioning from being a country that mostly relies on agriculture to a more service and industrial oriented economy. Many of the migrants are moving to the urban area, in the prospect of higher wages. The future threats of climate change and the rapid urbanization of HCMC creates many challenges for the urban development, at the city especially with its low-lying topography and exposure to sea-level rise (Schwartze 2016).

Vietnamâ&#x20AC;&#x2122;s Mega City The urban area is approximately 2095 kmÂ˛ with a population of 7.7 million. This number is constantly increasing and according to the UN and it has already turned into a Mega-City, reaching the benchmark of 10 million inhabitants (Schwartze 2016).

A view of HCMC from the Bitexco Financial Tower 19

Hoc Mon Dist.

Dist. 12 Thu Duc Dist.

Go Vap Dist.

Binh Tanh Tan Plan Phu Dist. Tan Binh Nham Dist. Dist. Dist dist. 3 dist. 10 dist. 1 dist. 11 dist. 4 Binh Tan dist. 5 dist. 6 Dist. dist. 8 Dist. 7

Dist. 9

Dist. 2

Nha Be. Dist.

Binh Chanh Dist.

10 km Rural Area Inner City Area

Diagram of The Inner City, New Urban Area and Rural Area of HCMC

Migration

$ $

New Urban Area

Economic hub

$ $

Rapid urbanization 20

Aerial map of Ho Chi Minh City The Saigon River meandering through HCMC. The city is sprawl21 ing into the rural area. The dense urban area is seperated by the many canals running through the city

10 km 22

A c i ty o f w a te r w a y s the many waterways and water resources in the Ho Chi Minh City Region

Ri v ers & c a n a ls

The rivers and canals Constructed and artificial canals have always played a role throughout the history of the civil society and HCMC is no different. Because the city is built on old marshland and located on the northern fringe of the Mekong Delta, the land is often affected by flooding caused by SLR and the monsoon rains. The construction of the canals started during the French colonial time, when they built drainage canals in the Delta. The canals had different purposes including, transportation connections and connecting the city to ports in the Mekong Delta. The canals were also used for flood control and water supply.

son, and flooding them in the wet season. These factors have influenced the ecological system in the canals. HCMC is largely exposed to SLR and is ranked as one of the top five cities in the world, in terms of the civil society being exposed to flooding caused by SLR. Flooding is a pressing issue in HCMC due to multiple factors. The low topography that most of the city is constructed on, 28% of the urban area lies 2 m above AMSL (Givental 2014) combined with the monsoon rains in the wet season, high tides and flooding caused by pluvial flooding, this means that the water is unable to enter the sewer inlets because of clogging or blocked sewer inlets (Givental 2014).

After the Vietnam War ended in 1975 (Givental 2014), the maintenance of the canals was neglected, and this caused the canals to become heavily contaminated by industrial and domestic waste (Givental 2014).

Polluted canals Another issue with the canals in HCMC is pollution. With an outdated sewage system and less to no organized solid waste collection, much of the solid waste from households and wastewater is being discharged into the canals, without undergoing any treatment. Thus, the canals are contaminated with inorganic and bacterial agents. In 2008 a report by HEPA (Ho Chi Minh City Environmental Protection Agency) stated that approximately â&#x20AC;&#x153;..150,000 cubic meters of industrial wastewater, 17,000 cubic meters of domestic wastewater, 400-500 tons of solid waste and 300 tons of human waste are disposed directly to the Ho Chi Minh City canals every dayâ&#x20AC;? (Givental 2014). The pollution of the canals is also caused by small food-businesses, textile, oil and chemical enterprises at a small family scale, who are discharging industrial waste water in the canals, without it undergoing any treatment (Givental 2014).

The historic use of the canals The canals have always been a proud element in the former city of Saigon, the capital in Southern Vietnam. But after the Vietnam War and the reunification of North and South Vietnam, many of the canals became publicly owned and were neglected. A majority of the canals went from being transport waterways, to being deposits for solid waste and sediments. Furthermore, many migrants settled along the canal banks in squatter housing that is known as the canal slums (Givental 2014). Flooding issues Over the past century the destruction of the mangroves in the Mekong Delta and SLR caused by climate change, the canals dry out during the dry sea25

10 km Ho Chi Minh City limit Inner Urban Area Rivers and Canals in the Ho Chi Minh Region Diagram of the rivers and canals in the HCMC Region

Old marshland

Old coastland wetland

Polluted canals

Water res o u r c e s in th e H o C hi M i nh C i t y R egi on

The water around the city At the far south of the Mekong Delta and before the rivers reaches the South Chinese Sea you find mangrove forest in the Can Gio area. The Mangrove is also known as the â&#x20AC;&#x153;green lungsâ&#x20AC;? of HCMC and is rich in biodiversity. Even though the city is located in an area that is rich in water resources HCMC is facing great challenges providing sufficient water to the urban dwellers. Not only can many of these waterways provide sufficient amount of water, it can also be used to transport away the wastewater.

and Bien Hoa areas, the discharge is found in many other canals that runs through HCMC. The Dong Nai River is not the only canal receiving wastewater from factories. Fiver other canal systems also receive wastewater from various different factories, manufactures and enterprises, and even without direct discharge the rivers are still receiving wastewater during the wet season. Cleaning the canals Action has been taken towards more clean canals in HCMC. The improvement of the Loc-Thi Nghe canal is one project, where residents of poor housing was relocated and the edges along the canal was changed into green areas. This initiative mitigated the pollution in the canal.

Wastewater treatment The industrial zone of HCMC is located at the north eastern fringe of the city and upstream of the Dong Nai River. The wastewater from this area is being discharged into the Dong Nai river and it is at utmost concern because the river is adjacent to a pumping station, that supplies water to the urban dwellers. Furthermore, the Dong Nai River also supplies drinking water to the people in HCMC and adjacent provinces. The wastewater is not the only a source of pollution. Run-off from agricultural land with high amount of chemicals and the use of pesticides also contributes to the contaminant load in the Dong Nai-Saigon catchment and watershed. Despite the fact that the industrial zone and most of the wastewater is discharged is in the Thu Duc

Creating environmental awarness There is a higher demand for creating environmental awareness via campaigns organized by different groups partly funded by the government. The public demands a more transparent policy on these matters. The government also acknowledge that public participation in the early stages of a project is of high importance, and can lead to a more successful outcome. This approach can also prevent complaints from occurring and ensure that the policy will be carried out the best way possible (Duc and Troung 2003).

A pumping station at the end of the Nhieu Loc-Thi Nghe Canal

Solid w aste

During the field work, I had a the opportunity to meet with the NGO ENDA Vietnam. They are currently working with independent solid waste collectors, to ensure better work conditions and higher wages. During the meeting and through my spatial analysis, it became clear to me that people, waste and water are interconnected see fig. 2.

of street cleaners, the clogging of the inlets can lead to flooded streets and buildings. The generated collected waste The amount of waste that is being produced corresponds to the income of the household. The higher the income, the more waste is being generated (Schneider et al. 2017). The mean rate of waste produced in urban areas in Vietnam is 0.7 kg/cap/ day (Schneider et al. 2017). A large part of generated waste is organic matter (Schneider et al. 2017).

A culturel issue According to the world bank, HCMC has reach the bench mark of being a Mega city and 10 million people will automatically produce an enormous amount of solid waste. By observing many locals on the streets and by discussing with a local Sweco employee it became clear to me that throwing waste on the street and putting out you garbage bins is culturally acceptable. This can cause the sewer inlets to clog, and without a sufficient amount

The average density in HCMC is 3400 persons/ km2 and is comprised of two million households (Schneider et al. 2017). 70% of the solid waste is collected by private waste collectors (Schneider et al. 2017) and 30% is collected by public waste collectors (Schneider et al. 2017).

ENDA Vietnam

people

ENDA stands for Environment and Development in Action It is a Non-governmental Organization

waste

Some of their main areas of operation includes: Community development, poverty reduction, environmental awareness, environmental and sanitation improvement, solid waste collection and composting and more.

water

Fig. 2 A circular system - People - Waste - Water

Information from a meeting with Mrs. Linh at the NGO ENDA Vietnam on March 14 2019

Working with independent solid waste collectors in HCMC raising awareness and trying to create better conditions for the independent solid waste collectors 2 sectors for collecting waste in HCMC: Public and independent (Informal meaning no policy to support them) Around 4000 independent waste collectors and 2000 public waste collectors The independent solid waste collectors collect 60-70% of the solid waste in HCMC The individual household pays the independent waste collector directly The current wage for an independent solid waste collector is 20-25000 VND per household The independent waste collectors often work in teams and can cover around 200 households per day The independent waste collectors work 364 days a year â&#x20AC;&#x201C; they only have one day off during the TED holiday Information from a meeting with Mrs. Linh at the NGO ENDA Vietnam on march 14 2019

3 1. Sewer inlet clogged by solid waste 2. Informal waste collector pushing her cart by hand 3. A woman collecting recyclable materials on her bicycle 30

Cl imate c h a n g e & its impac t on H o C hi M i nh C i t y

A vulnerable city HCMC is between the top 5 cities in the world, where the civil society is being largely exposed to flooding. Studies have found that from 1958 to 2007 there is an increase in temperature across the world. The average temperature has increased with 0.5-0.7 ยบC (Katzschner et al. 2016). Although there is not a clear pattern of an increase in precipitation in that period, the intensity of typhoons has in increased and occur more often the past years (Katzschner et al. 2016). Furthermore, the sea level along the Vietnam coast have risen with an annual rate of 3 mm (Katzschner et al. 2016) an oceanographical station in the north of Vietnam shows that the sea level has risen 20 cm from 1958 to 2007 (Katzschner et al. 2016).

ter levels the land is also subsiding (Katzschner et al. 2016). Almost half of the wards in HCMC are experiencing frequent flooding during the rainy season. The future effects of climate change will intensify the heavy monsoon rains, increase SLR and storm surges will be more intense and frequent (Katzschner et al. 2016). The consequences of the rapid urbanization From 1989 to 2006 the amount of impermeable surfaces in the urban area has doubled (Katzschner et al. 2016). The rapid urbanization of the city transformed natural habitats such as forests and wetlands with permeable surface, into urban areas with roads and buildings. Due to the amount of areas that have lost its function as a natural infiltration and evaporation, that prevented part of the city to flood, has led to an increase in surface runoff. Furthermore, the urban development in the southern and western part of HCMC is built on old wetland and riverbanks, decreasing the storage for the natural water network, and occupying areas that used to work as natural retention areas and floodplains (Katzschner et al. 2016). Hence the increase in precipitation and the intensity and frequency of the monsoon rains, will increase the surface runoff in the sealed off urban areas (Katzschner et al. 2016).

A low-lying vulnerable urban fabric With HCMC located on the northern fringe of the Mekong Delta and a large part of the urban fabric is built on old marshland. Approximately 60% of the city is at an elevation 1 m above sea level and 45% of the urban fabric is 0+1 m above sea level (Katzschner et al. 2016). Not only does this mean that the urban fabric is vulnerable to the aftermaths of flooding, but because of decreasing groundwa-

A flooded street in Ho Chi Minh City Image source: https://bobandsuewilliams.com/explore/Ho-Chi-Minh-City-flood/

Th e s o c i a l g r e e n c i ty the morphology and praxeology of Ho Chi Minh City

The urban s tr u c tu r e s & l andus e

The dense city HCMC has experienced rapid urbanization over the past years (Nigel et al. 2016). This increase in population growth and urban development has made HCMC especially vulnerable to the impacts of climate change. The urban districts that make up the inner city are particularly dense, with a population density between 28,000 â&#x20AC;&#x201C; 45,000 pers/km2. The reason for this high density in the inner city, was the need to adapt to the frequent flood risk, and this area is located at a higher altitude than the surrounding land. Developing on low-laying land The rapid urbanization of the city has led to urban development in the low-lying areas. In the north the elevation is between 4-42 m above mean sea level (AMSL) and in the south and coastal lowlands between 2-0 m AMSL(Nigel et al. 2016). 70% of the urban area is below 2 m AMSL (Nigel et al. 2016). This increase in urbanization to the south leads to increased exposure to flooding due to sea-level

Frequent flooded canals due to SLR

Impermeable surfaces = Surface runoff

rise. As of now, 32% of the urban area is exposed to flooding (Nigel et al. 2016), and when looking at the planned urban development, the flooding risk is likely to increase up to 48% of the built-up area (Nigel et al. 2016). Flooding is thus one of the most pressing issues of HCMC (Nigel et al. 2016). The rivers and canals of HCMC make up about 16% of the total area, with a total length of around 8000 km (Nigel et al. 2016). These water-ways are influenced by semi-diurnal tide and are subject to a high tide up 1.5 m AMSL (Nigel et al. 2016). The rapid urbanization of the city has led to an increase in impermeable surfaces increasing the surface run-off. Degradation of natural areas in the urban periphery and channeling of natural water ways has led to the loss of natural space for water retention and detention. The dimensions of the flooding risks are constantly changing because of the rapid urbanization and on-going urban development. Actions towards a more resilient city Among the local authorities there is an agreement

Rapid urbanization

that a change in the planning model is needed, in order to make the city more adaptable to the impacts of climate change. Land-use planning can be an active tool to ensure an urban development that is more resilient towards future climate change. At the same time maintaining and preserving natural habitats that absorb the potential impact of climate change, such as natural retention and detention areas, cold air generation areas and protecting mangrove forests, can help build resilience and reduce risks that are prevalent in HCMC. In order to make the city more resilient towards climate change there is a need for the local authorities to integrate scientific results into their planning process.

ments and instead of creating large green area in the periphery of the city, make a patchwork of green spaces that can target multiple goals such as agricultural lands, flood protection and storm water management. Different planning methods can be taken into action. Small interventions at the household level, could include planting trees for shading and implementing on-site retention or retention systems. Thus, increasing the green and blue infrastructure and enhancing the green public space whilst creating a sustainable urban drainage system. One of the great challenges within this field, is to create a known platform for local stakeholders, authorities and most importantly the civil society (Nigel et al. 2016).

A blue & green solution within the built-up environment The built-up areas can be optimized by creating more green open space within the existing settle-

2 1. Dense urban area in dist. 1 2. Narrow alley in dist. 1 illustrating the dense urban development 36

The green c ity

Greening the grey HCMC is today a fairly green city. From small parks to larger parks, street trees, planters along the roads, groundcover greening underneath overpasses ang greening along the canals. Along many of the boulevards you would see tall trees providing shadei n the streets and sidewalks. Great examples of how vegetation have been used as division for cars, motorbikes and pedestrians can be seen along Vo Van Kiet in dist. 1. Vegetation is also used to cover concrete walls i.e. walls in connection with a bridge see picture three. Greening the non-spaces According to the locals a more recent initiative by the government has been implemented. Groundcover and smaller trees has been planted under bridges or overpasses see picture 2. This creates a more inviting environment and you can see people sitting on the paths going through the vegetation. In some areas it also connects the slum housing area on the canal banks with the built-up urban environment.

Greening of canals

Vertical greening

Locals greening the alleys and buildings

Walking around HCMC you will see various different parks from big public parks with security and park rules stated on signs when you enter the park. In the different neighborhoods you will also see smaller parks, with exercise equipment that is very popular during the morning and evening, when the temperature is more suitable for outdoor exercises. Locals greening their city In the small alleys the residents put out ornamental trees, hanging plants from the many balconies and smaller potted plants by the doorways. Creating a contrast to the concrete pavement and brick and concrete buildings. The green goal Green spaces are an important element when designing more sustainable cities and especially in terms of flood control. HCMC are aiming towards providing 7km2 of greenery per habitant. This can be seen as an ambitious goal, due to the fact that in 2016 the greenery provided per habitant was 0.7 km2 (Katzschner et al. 2016).

Street trees

Greening under overpass

1. Greening and park area along the Tan Hoa Lo Gom Canal 2. Groundcover plants and small trees under an overpass, with small paths inviting people in to walk around 3. Vertical greening covering i concrete wall supporting a bridge

Li fe of th e s tr e e ts - th e soc i al s i dew al k s

A multi-functional space The sidewalks in HCMC is much more than just an area for pedestrians, in most cases it can actually be quite difficult to walk on the sidewalks. The sidewalks can be seen as a public space in the city where various different activities are going on. All over the city you will see small street vendors setting up in the morning and stay there for most of the day or set up again in the evening . They sell everything from coffee to fruits and vegetables to traditional Vietnamese food and desserts. Sometimes you will see the police ask the vendors to clear out, but soon after the police is gone, the street vendors will set up again. Many of the smaller restaurants and street vendors, will use part of the sidewalk as their outdoor serving area, setting up small plastic chairs and tables. Many of these establishments quickly fills up around lunch and dinner time. It is a social gathering place for families, friends and colleagues and you often see people sitting out until midnight.

Through field observations it is very clear that the space on the sidewalks works as a multi-functional space, and a large amount of the space has a social function for many of the locals and in some parts of the city also tourists. Walking pass some of the same street vendors every night, it quickly became clear that they often set up in the same spot every day. Another typical thing you will see on the sidewalks of HCMC is parking of motorbikes, mostly in connection with a coffee shop, a restaurant or a small shop and you will often see security guards outside these businesses coordinating the parking, in some cases also working as a valet. It is at utmost importance to take this into consideration when designing landscape-based stormwater solutions, making sure to keep the social sidewalk multifunctional.

$ $

Restaurants & shops

$ $

Street vendors

Parking

$ $

Restaurants & shops

1. A restaurant with outdoor seating, taking up most of the sidewalk space 2. A small shop where a group of men have settled in some chairs outside the shop, occupying the sidewalk 3. Sreet vendor selling produces on the sidewalk

A c a s e s tu d y a spatial study of three sites in Ho Chi Minh City

Spati al ity & g r e e n in fr a st r uc t ur e

In the previous passages I have looked at Vietnam and HCMC, introducing relevant background knowledge, on geography, the Vietnamese culture, morphological and praxeological aspects of the city as a whole. This chapter is a case study, looking at three specific sites in HCMC. Introducing theories and methods used to analyze and compare the three sites.

ment serves multiple purposes and many aspects of the human culture relies on water. Maintaining and ensuring good and healthy hydrological system is crucial (Ahern 2007). The Patch - Corridors - Matrix Model To understand the spatial configuration of the urban landscape, a universally accepted model can be used (Ahern 2007). This model also known as the Patch-Corridor-Matrix model is used in applied landscape ecology. It defines the urban landscape in three different categories; Urban Patches, Urban Corridor and Urban matrix see fig. 2 (Ahern 2007). An Urban Patch is defined as a homogeneous non-linear area, that is different from the surrounding area. The Urban Corridors is a linear shape which contents differs from its context. An Urban Matrix is defined as a piece of land or larger area where the dominant land cover type defines the area (Ahern 2007).

Sustainable adaptation With climate change there has been an emerging focus and awareness on creating more sustainable cities. Sustainability is understood in a broader sense, covering equity, environment and economy – this is also known as the “three E’s” of sustainability. One approach towards more sustainable cities is Green Infrastructure (GI). This approach targets abiotic, biotic and cultural goals. This is also known as the ABC resource model and includes not only the natural and build environment, but also the society. Thus, it also recognizes the needs of the public and this can play an important role, when designing sustainable solutions in the urban fabric and can ensure a foundation of public support. The GI approach needs analyzing on multiple scales in order to get a greater understanding of the system, function and connectivity. This multi-scale approach includes spatial configuration of ecological processes and landscape patterns. This can help indicate where in the urban landscape strong links enhances the connectivity and where these links are missing or can be improved (Ahern 2007).

The five GI approaches Five different approaches can be looked at when planning and designing GI; Articulate a spatial concept, Strategic thinking, The greening of infrastructure, Plan for multiple use and Learn by doing. Articulate the spatial concept is often related to the culture and public in the specific area you are working with and it can help support and inspire planners and designers when planning and designing GI. Strategic thinking is important in order to ensure an approach, that is appropriate to the spatial context and to aim for the most suited planning goals. The greening of infrastructure is a term that include a variety of green storm water systems e.g. green roofs, bioswales, wetlands, retention / detention

Water is an important element when studying connectivity in the urban fabric (Ahern 2007). This ele-

ponds etc. One of the advantages of green urban infrastructure is the opportunity to create spaces with multiple use. This can also be cost effective and is often supported by the public.

The learn by doing approach is often used when applying landscape-based ecology. This is due to the lack of empirical evidence in these often site-specific projects. (Ahern 2007).

Urban Patches

Urban Corridors

Urban Matrix

Parks Sport fields Wetlands Community gardens Cemeteries Campuses

Rivers Canals Drainageways Riverways Roads Powerlines

Residential Neighborhoods Industrial Districts Waste Disposal Areas Commercial Areas Mixed Used District

Fig. 2 Examples of elements in the Patch-Corridor-Matrix Model (Ahern 2007)

Greening used as a structural division between cars, motorbikes and pedestrians, Dist. 1 HCMC

Site I Site II

The l ong lis t Cas e stu d ie s

Site III

The theories and methods presented in the previous section has helped shape the field work into a more structured and focused analysis. The selection of sites for the case study, are based on a long list. The list is based on map research and literature study prior to the field work. These criteria support the research question, in terms of spatiality and possibility of implementationand are important factors, in terms of answering the research question. Furthermore, Sweco had already conducted surveys in dist. 8 and 4, hence data within these two districts was accessible to me.

The long list see fig. 4 is a list of criteria, set up to select three case study areas. To investigate and analyze the three sites, I was inspired by the Patch-Corridor-Matrix Model. Based on map research of HCMC, modifications of the model were made, to accommodate the setting it was to be used in see fig. 4. The registration on site focused on the elements in fig. 5, investigating the quality of these modified urban patches, but was not limited to the modified model. The morphology of the urban matrix and the possibilities for landscape-based stormwater management, was also looked at and taken into consideration, when investigating the three sites. Based on the analysis, challenges and strengths in the three different sites, one case area was chosen as a representative for similar areas in HCMC.

Dense urban area River or canal in the area Medium to low income residential area Few to no high-rises Mixed used area Fig 4 The long list

Modified Urban Patches

Parks Sportfields Wetlands Community gardens Vacant lots

Parks Green Patches Greenery around waterbody i.e. along the canals Community gardens Vancant lots/Non-spaces i.e. under a bridge/overpass

Fig. 5 Modified Urban patches based on the Patch-Corridor-Matrix Model

Dist 11 Dist 4 Dist 5

Dist 6 1 km

Dist 8

2 km

3 km

4 km Diagram of dist. 8 and 4 where the three sites are located

Example of a green urban patch under an overpass and next to a canal

Si te I

Site one is located in district four. It is a mixed used area with industrial buildings along the canal and the Saigon river. The river is approximately 300 m wide from the one riparian zone to the other, this is more than three times as wide as the canal in the south end of the area.

benches or raised planters in the park. When you went further on into the more build area of the site, many of the streets and alleys were very narrow and the space between the buildings was very limited. As many of the other mixed-used areas small street vendors and shops facing the streets were observed, contributing to the social life on the sidewalks.

There are two public parks located along the canal and a smaller green patch with exercise equipment. All three green areas seemed popular with a fair amount of people using the areas during the morning to mid-morning hours. People enjoyed the shades from the trees and used the exercise equipment during the cooler morning hours. They were all very well managed. In one of the parks you could walk along the waterfront or sit on the many

The amount of road trees was very limited in this area. Making it a less green site compared to the other sites. Some of the streets was not paved, hence the was a lot of dust in the air, this also made it less comfortable to sit on the sidewalks.

1000 m 800 m 600 m 400 m 200 m

3 4 2

Diagram of site I

1. Houseboats along the canal from where they sell produces to the street side 2. A small shop on the ground floor open towards the street, making it a place to sit and take a break and look at the streetscape 3. Public park adjacent to the canal with lots of trees. Many locals where seen sitting and relaxing in the shade 2

4. A wide road with a few road trees

Si te II

The canals work as an organic boundary for this site. The area is a mixed-used area from low income squatter housing along the many canals to build up shop houses in three to five stories, new development is also seen in the area in the form of high rises. Hence the area is very diverse in terms of residents, economic status and lifestyle.

mosphere is of course very different. The streets are less busy and the sidewalks are mainly used by pedestrians. Small planters presumably placed by the residents, adding to the aesthetic value of the streets. The street typology varies from wide roads approximately 8-15 m to small alleys approximately 1-3 m wide. The surface is primarily impermeable and many of the streets are constructed of large concrete slabs or asphalt. All around this area street trees are scattered and climbing plants growing on the residential buildings. The climbing plants are also used to cover vertical surfaces such as concrete walls in connection with a bridge.

Along many of the busy streets there are small streets vendors and shops open towards the streets, making the sidewalks a social space, as you see all over HCMC. The shop and street kitchen owners usually live in the back of the house, turning the front of their property into a shop or restaurant in order to make a living. In the parts of this area that is primarily residential neighborhoods, the at-

1 4 3

200 m 400 m 600 m 800 m

1000 m

Diagram of site II

1. Informal settlements along the canal and high-rises in the background - a typical picture of the urban development in HCMC 2. Low lying street next to a bridge with housing on the same level as the street - this can have severe consequences for the residents i case of a heavy rain event 3. A colorful shophouse - a very typical building typology 4

4. Informal urban settlement housing

Si te III

Site number three is fairly different than the other two sites. It is located right on periphery of the city, the buildings are mostly new development 3-5 stories residential buildings, temporary housing for seasonal workers, vacant land that is most likely to be occupied by new residential buildings in the near future and small patches of agricultural land.

was a very quiet neighborhood during the day when the site visit was conducted. Around the residential area small benches were placed on some of the sidewalks. Many of the sidewalks in the newly developed area was not maintained and weed was growing between the cracks in the concrete. In one of the vacant lots a small community garden with vegetables and other edible species were growing and looked fairly maintained, this I presumably an initiative made by the local government, and a way to utilize the open space until construction would start.

The streets in the area are wide and open, some of the streets are paved and others are just loose gravel. Along the road close to the canal you can find shops, street vendors and restaurants and this is where most of the social life is happening in site three. The area was primarily a residential area and

1000 m 800 m 600 m 400 m 200 m

4 2

Diagram of site III

1. Small agriculture patches in between water ponds 2. Temporary housing for seasonal workers provided by the local Government 3. Narrow path between temporary housing 4. Vacant land in between new development - very characteristic for site III

Chal leng e s & s tr e n g th s

Similarities and differences The three sites were chosen based on the longlist and map research. When visiting the sites, it quickly became clear that the sites are different and unique in their own way. All of the three sites had different challenges and strengths but are all facing the same threat of climate change â&#x20AC;&#x201C; frequent flooding during the wet season due to the topography of the land and the many impermeable surfaces.

two sites. With the location on the periphery of the urban area, part of the site was small patches of agricultural land. It was also very clear that this was a newly developed area. The majority of the buildings were newly constructed residential buildings and some temporary houses. Some of the temporary houses are rented out by the local government to seasonal workers, who most often lives in the countryside, and moves to the city a few months a year to work. The many vacant lots in this area and the location (on the periphery of the city) could mean more space for green stormwater infrastructure. The opportunity for creating larger wetlands and retention/ detention areas were many in this area. But the site did not meet many of the criteria on the long list and did not seem very diverse in residents.

The majority of the social life in HCMC is happening on the sidewalks. This is where the street vendors settle down for the day, the different shops use the sidewalk as works space as seen on picture 3. Restaurants and coffee shops use the space as their outdoor seating area. This is a major challenge when designing green stormwater infrastructure, because most of the space that can be used for landscape-based stormwater solutions is occupied, hence the need for multifunctional solutions are of high importance.

Site II - The selected case area Site number two was the site that met most of the criteria on the long list. It is a site with high diversity in spatiality, residents, building typology and use. One of the biggest challenges of this site is the lack of space. Many of the sidewalks on the busy and larger roads are occupied by street vendors, shops, restaurants etc. Through literature research and field observations it became very clear to me, that there is a need for a patchwork of green stormwater infrastructure in these very dense areas. With many impermeable surfaces and clogged sewer inlets, the water has nowhere to go but inside peoples home and flooding the streets for days. Site 2 has been chosen as the case area for further investigation of the opportunities for a patchwork of landscape-based stormwater solutions.

Site I Site number one was primarily a medium income mixed used area, and industrial buildings along most of the waterfront. Most of the squatter housing along the canal had been relocated to a different area in HCMC and actions towards a more flood resilient area had already been taken into action and the construction for those initiatives were already in progress. Three public parks were located in the area. These parks seemed popular for the locals to sit in the shade and relax and for exercise. Site III Site number three is fairly different than the other

1. A fairly new initiative by the government - greening under bridges 2. A canal can have multiple functions during the rainy season such as conveyance for water or detention basin 3. This is a good example of how many of the sidewalks in HCMC looks like, occupied by different small business, street vendors etc.

Th e s e l e c te d c a s e a r e a investigating the morphology, praxeology, needs and wishes from the locals

Si te II - T h e c a s e a r e a

This area represents many of the different aspects you see around HCMC. It is a mixed used area with both new and older development. The area is surrounded by canals and you can find everything from slum to new midlevel income residential areas and high-rises are currently being built in the area. It is a very dense area, with many impermeable surfaces. As many other parts of HCMC the streets are fairly green with street trees, groundcover and smaller tress under overpasses, green canal banks and greening of vertical surfaces. The sewer inlets were clogged even though the site visit was conducted during the dry season. This indicates that there is a need for an upgrade of the

sewage system and that there is a need for landscape-based stormwater solutions that can manage some of the rain and stormwater during the wet season. The area is approximately 1.35 km2 and there is only one park. It is a small approximately 4000m2 community park with exercise equipment and a playground. It seemed like a popular space during, hence people were spotted during the day. As mentioned above other green initiatives had been implemented in this area, but it seems that the primary function of these initiatives is aesthetics and plants help mitigate the UHI effect.

P 58 1. A view of the dense urban fabric in the pilot areae in dist. 8 2. A smaller canal in the pilot area with lush plants in the riparian zone 3. Narrow street between low industrial buildings - all impermeable surfaces

Slum along the canals

Greening under overpass

Street trees and social sidewalks

Narrow alleys for motorbikes and pedestrians

Diagram of the selected case area - Site II

Vegetation along the banks of the canal, social sidewalk and slum along the banks of the canals

Residents greening the exterior of their building

Vegetation along the bankâ&#x20AC;&#x2122;s of the canals and social sidewalk 60

Narrow alleys for motorbikes and pedestrians

Street typ o lo g ie s

To get a greater understanding of the site and possibilities for implementing a landscape-based storm water management solution a spatial analysis was conducted. Three main street typologies were identified in the area; Large (L), Medium (M) and Small (S).

day and evening and a big part of the social life is seen on the sidewalks. The buildings defining the street space are typically 3 to 5 storey shophouses and 5 to 10 storey office buildings. Small (S) The smallest street typology seen in the areas are small alleys, street typology S.- They can be down to one meter in width and up to 3 m wide, most of the traffic in these alleys are motorbikes, pedestrians and bicyclists, but cars can be seen in the wider alleys. The space in the alleys are defined by 3 to 6 storey residential buildings or smaller one-storey manufacture box buildings.

Large (L) The L street typology is a major road between 10 and 15 m wide, most of them have 4 lanes. The sidewalks are between 3 to 5 m wide and is most often being used by pedestrians, motorbikes, and small street vendor were seen scattered along the sidewalks. During rush hour these streets are busy, but outside of rush-hour, some of them are almost deserted and with few vehicles.

Exceeding the case area These three street typologies have been identified, in order to make contextual landscape-based stormwater solution that does not compromise with the streets and social sidewalks. It is also important to note that all of the streets are constructed with impermeable surfaces, resulting in flooded homes, restaurants, factories, shops etc. The three typologies are also very characteristic for most of HCMC and can be identified in most districts.

Medium (M) Street typology M are streets with a width of 5 to 8 m with two lanes. The sidewalks can vary in width along the road, but are most often between 1 to 3 m. Most of the space on the sidewalks are occupied by outdoor seating areas for restaurants, street vendors, small shops that set up some of their merchandize on the sidewalks and parking for motorbikes. These streets are busy throughout the

L: Wide streets with mid to highrise buildings

M: Smaller steets with many shops, small business and street vendors taking up most of the space on the sidewalks

S: Alleys mostly residential buildings 62

The need s & wis h e s fr o m t he l oc al s

The design proposal is for the people of HCMC. They are the ones living there and using the space every day and are the local experts on the praxeology of the street and urban space. It is important that the design, does not compromise with the life of the streets and does not intervein with peopleâ&#x20AC;&#x2122;s livelihood. Talking to locals, with the help of a translator, I was able to get a unique insight, to what the locals need and wish for their community.

sidewalks for their business, hence their livelihood depends on the space of the sidewalks. Because of the climate and the many impermeable surfaces, it can be very hot in HCMC. Many of the lower to working class people spent the majority of their time outside and there is a wish for more trees in the streets, that offers shading, in areas where people sit down e.g. next to a street vendor. A local told us that they had come together in the community and was encouraged by the local government, to take initiative to stop the flooding in their small neighborhood. The residents came together and collected enough money to make a small-scale flood protecting by raising curbs. Because the existing terrain is slopping towards an adjacent canal, they were able to design an inexpensive solution that could convey the water to the nearby canal.

I was told that the flooding often happens during the evening or night, and the streets sometimes stay flooded seven to ten days. It puts a huge constraint on the locals, when their homes and small business becomes flooded, it is impossible for the street vendors to set up their shop, during this flooding period, which means they will lose their income for up to 10 days.

All of this information that the locals provided was taken into careful consideration when designing the landscape-based stormwater solutions.

As mentioned previously the, sidewalks are not just for pedestrians, but has a multifunctional use. People often from poor income households, have their small business on the street level and use the

P 64 1. A local woman sharing her wishes and needs for the neighborhood 2.Two men transporting goods on a mopet with a flatbed 3. Man sitting on a bench along the Nheu Loc Thi Nghe Canal

Th e d e s i g n three contextual landscape-based stormwater solutions supporting the social life of Ho Chi Minh City

The desig n

Contextual design solution based on Detention, conveyance and evaporation The design proposals are based on three fundamental landscape-based stormwater solution principles; Detention, Conveyance and Evaporation. The three landscape-based stomwater solutions are contextual solutions emerging from the wishes and needs from the locals, gathered through field research and informal interviews. Furthermore, the field observations have contributed to the understanding of the morphology and praxeology of the streets in HCMC. Understanding the space and social conduct has been an important factor, in order to design a solution that does not intervene with peopleâ&#x20AC;&#x2122;s daily life and livelihood an improves the quality of lived experience after a stom event.

Designing for the people of Ho Chi Minh City The contextual designs are exemplified in the case area, with illustrations and renderings. The solutions are not designed exclusive for the case area but are solutions that can be adapted and implemented in most areas in HCMC. It has been a crucial design criterion, that the solutions can be implemented in the built-up environment, in ways that provide safety and beneficial spaces for low-income families without compromising the use of space. Thus, a community-based adaptation approach plays an important role for the design of sustainable and feasible solutions in order to create an integrated design, in terms of use, aesthetics and simple technology. The proposed design solutions supports the social life of HCMC by enhancing the livability in dense urban areas.

Detention

Conveyance

Evaporation

The desig n - Co n c e p t fo r t he S w al e Evaporatio n The Swale is the vegetated stormwater solution with evaporation as its primary function. The size of the swale can be modified, so it fits the surroundings it is implemented in. It is designed with 40 cm of mulch, so the plants can thrive, an underground reservoir with chippings, and an under-drain to convey the water, to a detention basin. It is encouraged to plant species that can be found in the HCMC Region, to ensure the plants will thrive. Examples of such species can be found next to the illustration of the swale (see opposite page).

green division between vehicles and pedestrians and create a safer space for the people using the sidewalks for various activities, which is an important part of the urban culture. The main function of the Swale is evaporation and evapotranspiration. The vegetation will have a cooling effect and reduce the UHI effect. The solution will also add aesthetic value and increase safety in the streets and neighborhoods. If the Swale is being implemented over a longer stretch, it is suggested that chippings made from recyclable building material, can be laid out perpendicular to the Swale, so people and motorbikes can access the sidewalk and to make sure that the Swale does not become a barrier. It was observed that most of the larger roads have crossfall and therefore the swale is placed in the side of the road. If enough space is available, it is encouraged to implement the swale in both sides, in order to decrease the surface runoff.

There was a wish from that locals that more trees should be planted in the urban area, because they provide shade and cooling effect. It is important to note that if trees are planted in the swale, they will need a separate plant bed with a root barrier ensuring the roots not to damage the under-drain. Implementation The example illustrates the Swale implemented along the larger roads. It will become a dynamic

1:200 Trees e.g Albizia julibrissin, Melaleuca quinquenervia and Terminalia catappa

Vegetation e.g Saccharum officinarum and Rhodomyrtus tomentosa

Under-drain Ă¸ 400 mm

Illustration of the Swale

Shophouse

Sidewalk 4m

Concrete corner stones Mulch 40 cm Reservoir Under-drain

Road 10-15 m

Sidewalk 4m

Office building 1:200

The desig n - Co n c e p t fo r t he S w al e Evaporatio n

Private rooftops with planters

Social sidewalk with small businesses, street vendors and parking for motorbikes

The swale is a green division between the people and the traffic, creating a safe space for pedestrians and the street vendors. A resevoir is implemented to increase the water capacity and an under-pipe in the bottom to convey the stormwater away

Shophouses and office buildings with private rooftops. The shophouse is a typical building typology that can be seen in most areas in HCMC

Trees are plantet on the side of the swale towards the sidewalk. The trees provide shade for the people on the sidewalk, add capacity for evaporation, in addition it can reduce the UHI effect

Swale with vegetation that can be found in the HCMC region. A permeable path made of stones connects the street with the sidewalk, so pedestrians and motorbikes can cross

Isometric illustration of implementation of the Swale in street typology L

Rendering of the Swale

The desig n - Co n c e p t fo r t he Tr enc h Mul ti-func tio n a l Implementation The size of the trench can be modified so it fits the street and needs in the area and is solely replacing part of the sidewalk, not taking up any space from the streets.

The Trench is a multi-functional landscape-based stormwater solution supporting the social life of the sidewalks in HCMC. Through field observations and discussing needs and wishes with the locals, it became very clear that there was a need for a solution that decreases the amount of surface runoff, but at the same time does not take up space that is used by the streets vendors, restaurants, small shops, parking of motorbikes, and other sidewalk activities.

The trench is constructed of chippings, made from reused construction material, to make the solution more sustainable. It is important to note that the size of the chippings has to be the same size, in order to make sure the water can penetrate. As an experiment, bamboo is used as underground stabilizers to ensure the road and sidewalk structure does not collapse. This solution also has an under-drain, to make sure that the water can be conveyed during heavy rainfalls.

To accommodate the wishes and needs of the locals this solution also propose trees and it should again be noted that if trees are planted in the trench, they will need a separate plant hole with a root barrier ensuring the roots not to damage the under-drain.

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Trees e.g Albizia julibrissin, Melaleuca quinquenervia and Terminalia catappa Chippings made from recycled building material. All stones must have the same grain size to ensure penetration

Underground stabilizer constructed with locally grown bamboo Illustration of the Trench Under-drain Ă¸ 400 mm

Office building

Bamboo Stabilizer Plant hole Reservoir Under-drain

Street 8m

Sidewalk 3m

Shophouse 1:100

The desig n - Co n c e p t fo r t he Tr enc h Mul ti-func tio n a l Shophouses and office buildings with private rooftops. The shophouse is a typical building typology that can be seen in most areas in HCMC

The trench is constructed with recycled building material, and makes it possible for people to still use the space for various activities. The underground reservoir increases the water capacity and an under-drain is installed to convey the water from the system to a detention basin

Private rooftops with planters

Trees planted on the side of the trench towards the sidewalk to provide shade for the people on the sidewalk

Isometric illustration of implementation of the Trench in street typology M

Rendering of the Trench

The desig n - Co n c e p t fo r t he R i l l Conveyanc e The third and last solution is a rill, designed for the many narrow alleys in the dense urban environment. The alleys are between 1 and 3 m wide, and are most often used by residents, pedestrians and motorbikes. The Rill is a narrow landscape-based stormwater solution, and the main function is to convey the water away from the streets. To increase the capacity, an underground reservoir and an under-drain is installed. If the rill is implemented near a trench or swale, it would be feasible to connect the rill to one of the two solutions, in order to covey to water to a solution with more capacity.

of the alleys incline towards the center of the alley, hence the solution is suggested to be implemented in the middle of the alley. The chippings are made of recycled building material. It is again important that the size of the chippings are the same, to ensure penetration. To make the solution more sustainable and because there are few to no heavy vehicles in the alleys, it is suggested that local timber, such as bamboo, can be used as an underground stabilizer. Bamboo was seen used as scaffolding throughout various construction sites and it has a high tensile strength. Using it as an underground stabilizer, would be an experiment and HCMC and Vietnam could become known as an innovative region or country experimenting with sustainable, locally produced materials for climate adaptation.

Implementation The structure of the Rill is very is similar to the structure of the Trench. It was observed that many

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Chippings made from recycled building material. All stones must have the same grain size to ensure penetration

Underground divider made of locally grown bamboo

Under-drain Ă¸ 400 mm

Small manufacture

Bamboo stabilizer Reservoir Under-drain

Shophouse 1:100

Shophouses and office buildings with private rooftops. The shophouse is a typical building typology that can be seen in most areas in HCMC

The desig n - Co n c e p t fo r t he R i l l Conveyanc e

Small manufactures and enterprises can often be seen in between residential shophouses

An underground reservoir to increase the water capacity and an under-drain is installed, to convey the water away

Private rooftops with planters

Narrow alley, mostly used by pedestrians and motorbikes

Rill constructed in recycled building material, to make it more sustainable. The chippings all have the same grain size, to ensure water is able to penetrate, and pedestrians and motorbikes can easily navigate through and in the space

Isometric illustration of implementation of the Rill in street typology S

Rendering of the Rill

The desig n - Ca n a ls Detention

Tan Hoa Lo Gom canal dist. 6

The canals in HCMC make up approximately 16% of the total area (Nigel et al. 2016) and can be an asset to the landscape-based stormwater solutions. It is suggested that the canals are used as detention basins for the stormwater, by connecting the landscape-based stormwater solution to nearby canals. It was observed during the fieldwork that many of

the canals had extra capacity. Instead of relying on wetlands in the periphery of the city, the canals could be a temporary detention basin for the stormwater within the build-up environment, slowly discharging the water to a wastewater treatment plant, or conveyed to a wetland in the periphery of the city if the water is clean enough.

The desig n - Ov e r p a s s e s Detention

Rendering of an underground detention basin

According to the locals, the government has for the past year initiated a new green strategy underneath overpasses. Throughout the city, you can find small green oases, with paths leading you through green groundcover and smaller trees, and in the tropical climate it works as a cooling spot in the city.

The space over ground is already being utilized, and in connection to the landscape-based stormwater solutions, it is suggested that an underground enclosed concrete detention basin can be installed to utilize the space underground. These underground detention basins can be constructed in different sizes, and it is another way of using the space in the build-up environment for detaining the water, until it can be discharged to a wastewater treatment plant, or if the water is clean, a natural or constructed wetland.

To my knowledge this very unique for HCMC, and they have turned an urban space that is often occupied by homeless people and a space that can be unsafe, into a green oasis, that invites people in to enjoy the benefits of the shade and vegetation.

The val ues o f la n d s c a p e bas ed s t or m w at er s ol ut i ons

In recent years, many cities all over the world have experienced serious consequences of climate change, and the need for resilient cities are of utmost importance. Asia is like many other parts of the world facing the threats of climate change, and frequently flooded cities has become a wellknown phenomenon. With the rapid urbanization that is examplified by this focus on HCMC, there is a pressing need to create solutions that, while mitigating flooding, ensure a sustainable development and create a livable city.

the environment and how it will affect future generations. It is about creating simple solutions, looking at natural waterways, and combining functionality, efficient technology with high aesthetics. When designing landscape-based stormwater solutions, it is of utmost importance to work with the local environment and a community-based adaptation, to ensure a sustainable solution that supports the urban lifestyle and a solution that does not compromise with the social conduct. There is a competition for space in dense urban environments, thus multifunctional natural systems that can integrated in space and time are important. Dynamic landscapes can add adaptability and flexibility to the urban environment, help mitigate the UHI effect, and decrease the surface runoff - thereby mitigating the flooding of peopleâ&#x20AC;&#x2122;s homes and livelihood.

Blue and green infrastructure focusses on mobility, biodiversity, safety and recreation and are designs for the human scale, making people an integral part of the solution. By exposing people to a landscape-based stormwater solution, you also create awareness. People become one with the raindrop, and see how it travels, what it affects and what it can do. It can create awareness on how it affects

Bishan park, Singhapore - A project upgrading the capacity of the Kallang river and transforming the surroundings into a park Image source: http://www.landezine.com/index.php/2012/06/kallang-river-at-bishan-ang-mo-kio-park-by-atelier-dreiseitl/

Di s c uss io n & r e fle c tio n s

Discussion and reflection - Results This thesis focusses on contextual landscape-based stormwater solutions. They are thought to be feasible solutions that does not intervene with the social life of HCMC and mitigate flooding. The solutions are designed to manage stormwater on site and convey the stormwater to a detention basin. It is a contextual, meaning they are not designed for a specific site, but can be adapted and modified to be implemented in other similar areas.

Discussion and reflection - Method Informal interviews were done during a site visit. They provided an insight knowledge that added a unique value to the design solutions. Structured interviews could have added additional value to the solutions, and a more structured method, could have given a broader perspective in terms of the needs and wishes from the locals. It should also be taken into considerations that the conversations were translated, and some information might have gotten lost in the translation. Fieldwork in Vietnam was a challenge. Certain restrictions and cultural norms had to followed, and this affected the planned field work. But it opened up the opportunity to explore different districts in the city, that gave a more holistic view on the morphology and praxeology of HCMC.

The research question focusses on the implementation and social aspect of landscape-based stormwater solution. For further research it is suggested that hydraulic engineers could contribute to the solution, making the correct calculations according to the inundate for a specific area in HCMC. The calculations could support and add additional value to the solutions. Furthermore a technical input to the construction of the system in terms of the right size of the chippings and under-drain, in order to ensure that the system can manage the needed amount of stormwater, to prevent the streets from flooding during the wet season.

Conclusio n

Designing a landscape-based stormwater solution using HCMC as a case area, required an understanding of the city, the culture and social norms. Through a literature study and map screening, the complexity of Vietnam’s and HCMC’s history unfolded. To design a solution that can be implemented in the dense built-up environment, three case areas was looked at, and one area was selected, to conduct a spatial analysis. The wishes and needs from the locals was gathered through informal interviews. During the field work it became clear that the sidewalks in HCMC is not just a space for pedestrians, but a multi-functional space particularly for social gatherings and some people’s livelihood rely on the space. Landscape-based stormwater solution can add multiple benefits to urban spaces, including safe spaces for pedestrians, mitigate UHI effect and mitigate flood risks. It is an alternative solution to a conventional engineered sewer system, but the landscape-based stormwater solution takes up space, that can be used for other purposes. To accommodate the social life on the sidewalks and the many people whose livelihood depends on the space, a contextual landscape-based solution was proposed for three different street typologies.

Underground detention basin

The Swale with an under-drain

1. The Swale – A solution designed for larger roads, where the main function is to increase evaporation, by planting vegetation from the HCMC Region and to add capacity to the system an underground reservoir is proposed. The solution increases the safety for people occupying the sidewalks, because it works as a green barrier from the busy road. Trees can be planted to provide shade for people and create cooling spots in the city. 2. The Trench - This solution suggests using recycled building material converted into chippings to ensure that the space can still be used, and at the same time mitigate the flood risk by using the same grain sized chippings so the water can penetrate to the underground reservoir. 3. The Rill – The construction of the Rill is very similar to the Trench, but this solution is designed for the small alleys in the very dense urban area. This solution does not compromise with the current use of the space. All of the solutions have an under-drain so the stormwater can be conveyed to a detention basin. Two detention basins are suggested. The canals and an underground detention system can be implemented within the built-up environment.

The Trench with The Trench with an under-drain an under-drain

The Rill with an under-drain

A canal for detention

The Rill with an under-drain

Reference s

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The World Bank (2018) Rural population (% of total population) Available from https://data.worldbank.org/ indicator/SP.RUR.TOTL.ZS?locations=VN [accessed: 8 April 2019] The World Bank (2017) Population, Available from https://data.worldbank.org/indicator/SP.POP.TOTL?end=2017&locations=VN&start=1960&view=chart [Accessed 8 April 2019] Vo, P. L. (2007) Urbanization and water management in Ho Chi Minh City, Vietnam-issues, challenges and perspectives. GeoJournal 70, 75-89.

All photos and illustrations are by the author unless otherwise stated

Kites in Vinehome Central Park, Ho Chi Minh City