Design of the landscape diversity of commercial streets in the old downtown of Ho Chi Minh City

Ho Chi Minh City is a city with many cultures, architectural styles, and different lifestyles. This makes Ho Chi Minh City characterized as a diverse city satisfying the different elements: spatial diversity, cultural diversity. According to the Saigon master plan of Coffyn designed in the early 20th century, together with public spaces, the commercial areas of Ho Chi Minh City were also identified as the main points for the city development. Therefore, the commercial streets in its old downtown also showed very obvious diversity. Vietnamese people have adjusted the urban spaces planned by French people in order to match with their lifestyle for more than 100 years. Besides, many old commercial buildings have been demolished and replaced with new buildings, causing the disturbance of life and cultural values of the city, leaving many streets losing their original landscapes and getting the same style. Their uncontrolled diverse development causes the clutter, loss of order, and insecurity. From this above situation, the author has chosen the subject “Design of the landscape diversity of commercial streets in the old downtown of Ho Chi Minh City” in order to find the oriented development for those streets on the basis of maintaining and developing their inherent diverse characteristics.


Introduction
In some Asian cities, the landscape diversity has been formed naturally and maintained effectively [6].In European and US cities, there was a reconsideration on the theory of modern urban architecture and encouraging the trend to shift from planning method "template" to planning model "diversity, adaptation" [7].The theoretical and practical lessons learned from the success of landscape diversity design in developed cities such as Tokyo, Hong Kong have created the platform for the comprehensive development solution for the urban landscape design in Asia, including Ho Chi Minh city.The methods measure diversity indices have led to the expectations on establishing a scientific design method for the development of landscape diversity on commercial streets of Ho Chi Minh city.
From the late 20th century, there was the movement to support the idea of diversity, from residential component diversity, living space diversity to diversity of social institutions.One of the pioneers of this idea is Jane Jacobs (1916Jacobs ( -2006)), the famous American researcher [8].Following Jane Jacob, there have been plenty of research and designing about the ideal of

Materials and methods
This study is designed to conduct in seven steps Step 1.The concept of diversity and the concept of "designs for landscape diversity of commercial streets" Step 2. The landscape characteristics of commercial streets in the old downtown of Ho Chi Minh City Step 3. The scientific basis of design for landscape diversity Step 4. To classify and evaluate the groups of commercial street landscape in the old downtown of Ho Chi Minh City Step 5. To establish the criteria for landscape diversity of commercial streets in the old downtown of Ho Chi Minh City Step 6.To propose the design solutions for landscape diversity of commercial streets in the old downtown of Ho Chi Minh City Research Methodology: Methods of fieldwork; Historical Method; Methods of sociological surveys; Mapping Method; Statistical Methods; Analytical Methods; Integrated Method; Comparative method; Multi-criteria assessment Method [12,13].

4.1
Step-1: The concept of diversity and the concept of "Designs for landscape diversity of commercial streets"

a. Definition.
A diverse area is a place where gathers of many people with different of economic conditions, culture, race, gender, age, lifestyles [14]...The formation of many kinds of the building and many different compositions of populations is an essential feature in the diversity area [9].
b.The meaning of diversity.
-The Vitality of Diverse areas: The Diversity brings economic development and ecological balance to the areas (creating sustainable development basis) [15].
-Social justice: The diversity ensures the better access to resources for all social groups [15].
c.The factors that form the diversity.

The concept of "Design for landscape diversity of commercial streets"
"Design for Diversity" is a design used for the buildings or spaces that have the physical diversity elements.Physical factor is one of three key elements of a diverse area (Physical factors, Historical/economic/social factors and Policy factors).These factors have discernment and linked by a chain of interactions "Design for landscape diversity of commercial streets": the activities aimed at maintaining and developing the diversity of the physical elements which constitute the landscape diversity.https://doi.org/10.1051/matecconf/201819301017ESCI 2018 Fig. 2. The concept of "Design for landscape diversity of commercial streets".

Step-2: The landscape characteristics of commercial streets in the old downtown of Ho Chi Minh City
Experiencing the development periods: the period before 1858; 1859 -1955; 1956 -1975; 1975 to the present.
In the old center of District 3 (including Districts 1,3,5) have the typical streets with the characteristics represented for each district, and the most common ones in urban areas of Vietnam [16].
*  -The diversity index of the landscape The thesis uses Simpson's diversity index to measure the diversity index of the landscape.According to this method, the higher diversity index, the more diversity landscape exists in that area and its elements are almost of the same quantity [17].-Consistent with the characteristics of all street groups.
-Based on some design methods supporting the diversity urban.
-Based on the design experience for urban in the world.c.The theory basis of design solutions for diverse streets in old downtown of Ho Chi Minh City.
First of all, the diverse area needs to have a specific code to identify the diversity landscape characteristic and clarify into groups.
After that, each group is matched with the diversity criteria and design methods in order to test the suitability and adaptation to the diversity of each group.
Finally, proposing the appropriate methods for landscape diversity design to make the compliments of criteria, methods to enhance diversity landscape design.

The practical basis applied in landscape diversity design
a. Landscape diversity design in Chicago.
Including Awareness of the value of diversity in the community, to reduce the pressure to develop new projects, social connection, the role of the social unions.
b. Landscape diversity design in Tokyo.
Including Street landscape continuously changes over time; the street landscape has formed different areas with different characters, coexistence rather than elimination.
c. Landscape diversity design in Hong Kong.Including Flexible and opened plan for landscape diversity with friendly design, high building, and the surprising design.

Evaluation results about the characteristic of landscape diversity
Reviewed characteristic landscape diversity through two surveys results, including the diversity of the physical elements constituting the landscape, the diverse index calculation results of typical commercial streets in the old downtown of Ho Chi Minh City.-Wish to come: Depending factors: Beautiful, Open, Bright.Thus, the key influence elements are as follows (from highest to lowest level): Beautiful > Openness > Bright, Comfortable > Luxury, Traditional, Young > Modern.

Evaluation results about the landscape emotion
There is a large difference in assessment of landscape emotion about the landscape of 30 streets.The streets having high landscape diversity are more attractive than others.The favorite extent is less change with age (young -old) or trendy (modern-traditional), but more depending on the elements of open, bright, comfortable.

Setting specific identification codes of the typical street landscape groups
Specific identification codes of the typical street landscape groups are not only helping to maintain the characteristics of inherent landscape diversity but also help to improve the diversity of street landscape.So we need to select the characteristic landscape on the two requirements as below.
As the results of classification, evaluation characteristic landscape diversity, the features of the street groups show a lot of diverse variables which are measured by various indicators such as: trees, building functions, building age, building architecture, building height; building width, front yard, fence, parking area, building front facade (closed-opened), color, commercial type, traffic type, culture type, social type... Therefore, the street groups have the above-mentioned characteristics which get high diversity values need to use them in setting specific Code of standard landscape features.
Other features such as the water surface, opened-spaces, squares, the form of the combined building, subsidiary building, pavement width, alley, intersection…can not be measured diversity level, but these properties are also supportive landscape diversity [19,20].Therefore, it is possible to use them in setting specific Code of standard landscape features According to my finding, there is no clear relationship between the width of the road, building density, the coefficient of land usage and landscape diversity in the commercial streets.Therefore, these features are not used in setting specific Code of standard landscape features [21].

Checking the level of response to the criteria of landscape diversity design in each commercial street group of Ho Chi Minh old downtown
Based on the framework of criteria and methods of landscape diversity design, checking the table for each commercial street group was established.-Checking the level of response to the criteria of landscape diversity design.
-Selection of landscape diversity design way for each type of commercial and service streets in Ho Chi Minh city old downtown.

Fig. 4 .
Fig. 4. The Simpson's diversity index.Indicate high diversity: high scores (close to 1), low scores (close to 0) indicate low diversity.*The rubrick to emotionally evaluate landscape The perception of the street landscape includes beauty -ugly, light -dark, traditionalmodern ... (visual), hot -cool (touching), noisy -quiet (hearing) ... This research applies common assessment Japanese methodology and is based on the five-leveled scale (Godankai Hyōka)[18].b.The theory basis to create criteria, method for designing the landscape diversity * The theory basis to create design criteria From the theoretical basis: The conditions of landscape diversity of Jane Jacobs; Criteria for adaptive landscape diversity of Ian Bentley; The design criteria diversity landscape of Emily Talen; the thesis proposed four criteria for designing and landscape diversity: Combination criteria; Connection criteria; Adaptation criteria; Safety Criteria.* The theory basis to create design method Because of the physical elements constituting the street landscape includes two main factors: the block spatial element and the operation spatial element, therefore the design method for each group is followed these two factors.*The theory basis to create design steps -Based on the criteria and methods for diversity landscape design.

4. 6 . 3 .
Selection of landscape diversity design way for each type of commercial and service streets in HCM old downtown a. Common street group (PB): Streets having buildings with low-rise, row houses, local architecture.

Fig. 11 .
Fig. 11.Typical street group IB.d.Typical street group IIIA: Streets having buildings with low-rise, Western architecture.