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Overview
With its advantageous geopolitical location and long development history, Hanoi has become a critical center, exerting its influences on the development of the whole country in general and the North of Vietnam in particular.
For the recent years, Hanoi has undergone rapid development. Urban population growth has placed heavy pressure on social infrastructure and technical conditions, land and environment. With a view to effectively manage the urbanization and successfully implement the industrialization and modernization of Hanoi, it is required to analyze the current situation and propose relevant solutions to assure urban sustainable development. Based on research results from the project Atlas of Thang Long – Hanoi, other references and field trip reports, this paper examines the natural advantages and disadvantages to Hanoi’s socio-economic growth and introduces some solutions to the sustainable development of the city. Due to the limitation of data resources and research results, the area of Hanoi mentioned in this paper is based on the municipal border recorded before August 1, 2008.
1. The position and natural potentials of Hanoi
1.1. Location
Hanoi lies in the very heart of the North of Vietnam, surrounded by north-west and north-east mountain ranges, namely Hoang Lien Son, Con Voi, Tam Dao, and the North-east Arches. Therefore, many rivers such as Da, Thao, Lo, Chay, and Cau converge in this region and run to the Gulf of Tonkin [1]. Hanoi has many advantages in terms of natural conditions and resources, population flows and cultural exchange, and acts as a major driver for socio-economic and cultural development.
Hanoi is the significant center of politics, administration, culture, science, education, economics and international transactions of Vietnam. It is also the crossroads of important national and international routes, railways, airlines and river routes.
Natural resources are the driving force for socio-economic development of the city.
1.2. Geology and mineral resources
· Strata: Hanoi is located in a special geological structure with a long development history, but rather simple stratigraphy. Traces of geologic formations from the Neoproterozoic Era (one thousand to 570 million years ago, in bore holes and according to geophysical documents), Mesozoic Era (in which two geologic periods are Triassic, 241 to 235 million years ago, and Jurassic, 174 to 145 years ago) and Cenozoic Era (Pliocene – Quaternary. 5.2 million years ago till present) [8]. These complexes have very different appearance and are separated by great sediment breaks.
· Geologic framework: Hanoi geologic framework is generally based on the low structure formed in the Neotectonics, where rivers and seas deposited the Red River Delta – a mosaic of thousands of meters deep, including fine sediments, largely clay and sand on gravels [8].
Formed in the Tertiary, the framework is sustained by deep tectonic faults Dong Trieu – Mao Khe (National Route 18) and Red River, between which three other faults run nearly parallel with Red River fault, causing differential settlement, creating a terrace-like structure. Therefore, the area is likely to suffer from seism, including earthquakes and fractures.
The low structure is surrounded by ranges which have low amplitude of oscillation, and are called the transition zone between the deposited delta and the area under Chan Chim Mountain.
Neotectonics and modern tectonics of this region have the clearest impacts on the deposited delta: sustaining the tendency of deposition for alluvial flats, deforming of delta terrace I, II in the North of Red River and, causing constant changes of river-bed morphology. Particularly, the straight rectification of Nhi Ha has resulted in the picturesque setting of West Lake in Hanoi.
· Mineral resources
Within the compass of Hanoi, 82 mines and mineral resources ( including 8 major minerals) have been identified. Clay is the most popular, including kaolin, kaolin-clay, construction sand and peat. Other minerals such as construction stones, laterites and solution clay are rarer.
+ Construction materials include black sand, with 11 sand areas scattered from Vong La – Dong Anh to Van Phuc – Thanh Tri, some others along Duong River, the total reserve is 48.506 million cubic meters. Golden sand is rich in Ca Lo and Cong River, with the reserve of 53.76 million cubic meters. Trachit is found in Minh Phu – Soc Son (more than 8 million cubic meters), laterites in Soc Son (1.5-metre depth on average). Tile clay includes 36.82 million cubic meters of weathered clay in Soc Son, and 223.45 million cubic meters of Quaternary sedimentary clay in Dong Anh, Soc Son, Tu Liem, Gia Lam, Thanh Tri, etc.
+ Industrial minerals: In Soc Son, kaolin (23 million tones) is found in sloping hills and knobs, kaolin clay (22.5 million tones) in basins between mountains and plains, and quick clay (1.7 million cubic meters) in late-Pleistocene lake and marsh sediment. Drilling fluid clay (more than 4 million tones) is found in mid-Holocene bay sediment in Dong Da mine, peat (three mines, more than 3.5 million tones) is in Dong Anh and Soc Son.
· Ground water
The area of Hanoi has hydrographic units as follows.
+ The porous aquifer in mid-Holocene sediment (qh) exposes on the surface from beaches of Red and Duong River to the South; and form narrow belts along Cau and Ca Lo River in the North. The depth of this layer is from 9.2 to 3.3 meters, no or low pressure, total mineralization rate is under 0.5 g/l. Water quality is low, water supply is not remarkable.
+ The porous aquifer in Pleistocene sediment (qp) exposes as small areas in Soc Son, the rest is located 2 – 22 and 10 – 35 meters deep respectively to the North and and the South of Red River. Water is found in Pleistocene gravel-and- sand layer, fresh, under pressure but the pressure is low in some parts. The capacity rate (q) is over 3l/s.m, total mineralization is from very small to 0.78 g/l, arsenic content is very low, at – 0.33 mg/l. The water reserve is considerable and is an important water supply to Hanoi.
+ The fissure – bed aquifer in Pliocene sediment (n2) can merely be found in bore holes of 70 – 90 meters deep, from Dong Anh province to the South. In such places as bore hole P48N in Dinh Cong, LK9 in Yen Vien, the water quality meets the requirements for natural mineral water, thus can been bottled.
+ The fissure aquifer in the lower-middle Jurassic, Ha Coi formation (j1-2) is distributed within Soc Son province. The water quality is not very high.
+ The fissure aquifer in mid-Trias effusive basalt sediment (t) is unevenly rich. The water is fresh; from some bore holes the water quality meets the requirements for natural mineral water, thus can been bottled.
+ The fissue aquifer in Neoproterozoic – lower Cambri metamorphic rocks, Chay River formation (np-e1) is covered by Neogene – Quaternary. The supply capacity is limited.
+ Watertight formations in upper Pleistocene and lower-mid Holocene sediment include clay, grey-brown clay, silty clay containing plants, and peat. The hydraulic conductivity is 0.004 – 0.06 m/day.
+ The upper Jurassic – lower Creta aquitard formation, Tam Lung formation (J3-K1tl) in the Northweast of Soc Son, its capacity rate (q) is 0.002 – 0.046 l/s.m.
· Engineering geology
Relevantly to its tectonic and lithologic structure, the engineering geology of Hanoi’s platform is complicatedly differentiated. In the plain, within 20 meters from the ground, soil can be categorized into various types based on different ages, origins, components, status and quality. In general, engineering geology of suburban districts in the North of Red and Duong River have favorable conditions for engineering development (lightly lateritized clay - aQ13vp is easily assessible on the surface, the primary rock basement is rather shallow). Meanwhile, in central districts and suburban ones in the South of Red River, the majority of complexes are originated from rivers, lakes and marshes, with low bearing capacity (including clay, loam, sand, peat of various status, and mud - aQ23tb/ lbQ21-2hh). At some points of which the depth is more than 2 meters, the gray-green clay layer has rather good bearing capacity; however, the underneath is usually a weak pedologic horizon – clay mud and peat of low bearing capacity - m/ lbQ21-2hh, which may cause engineering accidents, demanding engineering conditions and increasing costs on basements.
1.3. Topography
The city typography is fairly simple. The hilly area is in the North, from Tam Dao Range to the Southeast, heights steadily decrease from 300-400 meters to 20-30 meters. The downstream plain of 12-15 meters high stretches from the foot of Chan Chim Mountain to Co Loa, continued by the Red River delta, of which the heights is 4-6 meters, possibly 10 meters in some places.
Geomorphology of Hanoi is characterized by three major criteria: a tectonic location in the continent top of Hanoi valley in Red River basin, a geographical location by the Gulf of Tonkin, topographical changes and exploitation by inhabitants, particularly dykes and embankment to deal with floods and inundations.
Before Neogene, around 20 million years ago, this area used to be a highland. Then with the formation of Red River Basin, the trough structure of Hanoi has been established by deposition – compensation mechanism (the more the structure sags, the more it is deposited), resulting in a sediment of 6-8 kilometers deep. The capital city has sagged no more than 1,500 meters, in which the depth of the Quaternary sediment has changed from 10 to 120 meters (the Quaternary has been enduring for the past 1.6 – 1.8 million years).
The location by the sea has made Hanoi a shallow marine bay in transgression, relevant to an interglacial period, and Red River has created here a huge alluvial cone called the delta plain. In regression, relevant to a glacial period, the bay margin expands toward the sea, then Red River turns the delta plain into a kind of downstream plain.
When the last form of Holocene plain has developed in a stable way, every raining and flooding season, Red River brings hundred millions of alluvia, aggrading more and more. However, for the past 1,000 years, the alluvial flat has splitted itself into two patterns: the outside-dike area aggraded yearly and getting higher and higher, and the inside-dike area remaining low for its lack of alluvia. Many primitive troughs in the plain remain their existence.
In general, Hanoi’s topography is diverse for its low mountains, hills and plains. The city’s major area is flatland, of which the height decreasing from the Northwest to the Southeast, corresponding to the flow of Red River. This may have much effect on city planning and socio-economic development of the city.
The city center and suburban areas are lowlands on a weak pedologic basement. The water level of Red River in flood season on average is 4-5 meters higher than the city platform. A number of lakes and marshes facilitate aquaculture and tourism. However, its depression may constrain rapid drainage, thus causing constant inundation in some localities in rainy season. The low and medium hilly and mountainous area in the North of Hanoi is advantageous to engineering, industry, forestation, and tourism of various types.
1.4. Climate
The climate of Hanoi has been formed and maintained by the tropical monsoon with cold dry winter and hot wet summer. The annual total radiation and radiation balance is under 160 kcal/cm2 and 75 kcal/cm2 respectively. Every year Hanoi is under the influence of around 25 – 30 cold fronts. Though the annual average temperature is not less than 230C, that in January is under 180C, and temperature amplitude in a year is over 120C [4].
The rainy season from May to October accounts for around 80% of the annual precipitation. The dry season mainly brings drizzles and last from November to April of the next year, in which December or January is marked with the lowest precipitation. In general, the annual rainfall in Hanoi steadily increases from west to east in the north area, decreases in the same direction in the south area, and increases from north to south.
The winter in Hanoi is bitterly cold compared to the South of Vietnam. The number of cold fronts, very cold and damaging cold days is higher. Cold weather last longer and drizzles are more frequent. The cold winter in this tropical area results in a unique winter harvest season for Hanoi and the North of Vietnam.
1.5. Surface water
As a part of Red River and Thai Binh River system, the network of rivers and lakes in Ha Noi is unevenly distributed, the density fluctuates between 0.1 – 1.5 km/km2 (including natural rivers with regular currents) and 0.67 – 1.6 km/km2 (including canals). The annual high-value specific discharge is located in the Northwest and Southwest of the city, and the value decreases eastwards. The annual discharge values in the Northwest and Southwest are over 20 l/s/km2 and 23 l/s/km2 respectively; and that in an area in the East is under 17 l/s/km2 [2]. Hanoi can take advantage of the huge surface water areas of passing rivers, such as Red River, Cau, and Ca Lo River.
One of the typical features of Hanoi is the network of numerous natural lakes and ponds, many of which, however, have been occluded as the consequence of rapid urbanization and lack of effective planning and management. The areas of some lakes, such as West Lake, Linh Dam, Yen Son, Bay Mau, Hoan Kiem, Thanh Nhan, and Dinh Cong, are quite large. Besides, many smaller lakes scatter among different districts. Not many cities in the world have such a number of lakes and ponds like Hanoi. The lake network has created many beautiful ecological landscapes, and helped regulating the water surface, and the local climate. It has also been valuable to tourism and entertainment activities.
1.6. Land
The majority of Hanoi’s area is fertile, highly valued for various purposes, particularly for agricultural production.
The land area of Hanoi is classified into 5 groups (with 14 sub-groups), in which 2 are distributed in the plain and a small one is in the hilly area of Soc Son.
- Sandy land (106.1 hectares) occupies 0.1% the city’s natural area.
- Alluvial soil accounts for the largest area of 23,533.3 hectares (25.6% of the natural area), formed by river deposition process. Alluvial soil is categorized into 7 kinds of distinctive features, but they all have such similarities as high fertility, other indicators are better than those of the same kind of land in other plains. Particularly, non-acid alluvial soil makes up a large area of 14,289.7 hectares (15.5% of the natural area), and facilitates vegetables and rice crops thanks to its advantages of light component, water discharge and high natural fertility.
- Infertile gray soil occupies 14,289.7 hectares, 15% of the natural area, is distributed in curving topographic areas and bank terraces. This kind of soil has been degraded in terms of physical and chemical qualities, with little clay, light components and infertility. Low-topography areas where water rich in materials is kept, with a bigger amount of clay, may form glay soil.
- Yellow-red soil occupies 5,790.0 hectares, 6.3% of the natural area, including land formed by the weathering of bedrocks, the thin layer, and land originated from ancient alluvia, highly fertile compared to gray soil.
- Ramp land occupies 44.2 hectares, 0.05% of the natural area. Unlike the groups mentioned, ramp land is formed by the fall of weathering products into a valley area, hence fertility rates are varied.
The total natural area of Hanoi is 92,097 hectares (the border identified before 1/8/2008), in which agricultural and forest lands take 47.4% and 8.6% respectively. The residential area accounts for 19.6%.
Based on the demand of land use in Hanoi, two groups taking a significant part in the city’s socio-economic development are land for agriculture and forestry, and for engineering and construction. The majority of land areas in central districts are considered unfavorable for construction due to such reasons as ground and surface water accumulation, ground settlement, fractures, landslides, and weak pedologic horizons.
1.7. Ecosystem
Some types of ecosystems in Hanoi are very distinctive such as hummocks in Soc Son, lakes in general and West Lake in particular, rural and urban ecosystem, etc. Ecosystems of hummocks and lakes are the most bio-diverse.
The city’s plant cover develops in wet tropical climate with a clearly cold winter, on hilly and periodically-flood areas. It is classified into three big groups in terms of origin and functions, i.e. natural plant cover, cultivated plant cover, and other types.
+ Natural plant cover only remains on hilly areas in Soc Son. A large part consists of natural secondary plants in poor forests where timber quality should be improved. The group is classified into: 1) Bushes and secondary grass cover in hilly areas; 2) Inundated secondary grass cover and aquatic societies along dams and lowland in the alluvial plain.
+ Cultivated plant cover accounts for the majority of the city’s natural area, including: 1) Wet rice in the deposited plains and bank terraces; 2) Annual plant and vegetable societies in plains and mountainous areas; 3) Perennial plant societies, including orchards, tea trees, mulberries, trees providing logs and shades, etc.; 4) Cultivated forests in the hilly areas of Soc Son and in a near future more forest areas by Red and Duong River. 5) Parks with leafy trees and gardening plants in urbanized areas.
- The rest consists of scattered plant covers: 1) In residential and working areas with a small coverage rate, 2) In lakes, dams, rivers, canals, etc., where water inundates profoundly, thus the plant cover include only sub-water aquatic societies.
With a long his history of agriculture and husbandry, many valuable plants and animals have been found in Hanoi. Many products and famous places can be named as follows: Ngoc Ha flower village, Nhat Tan cherry garden, Nghi Tam mandarin orchard, Vong green stick rice, Me Tri rice, Canh orange, Dien pomelo, Dam Set anabas, etc. They have become cultural symbols and spots of attraction to Thang Long – Ha Noi.
In general, Hanoi’s plant cover has witnessed radical changes for the past few hundreds of years. With the advantage of fertile land and numerous specialties, Hanoi’s suburban agriculture is considerably potential to develop and serve the city demands.
Groups of plants and animals in Hanoi’s distinctive ecosystem are relatively diverse. According to current statistics, the species are as follows 655 higher plants, 569 mushrooms (lower plants), 595 insects, 61 terrestrial animals, 33 reptiles and amphibians, 103 birds, 40 mammals, 476 aquatic plants, 125 aquatic animals, 112 fishes, 48 imported goldfishes [5]. Among those creatures, many are of high economic value, many are very rare and can be found in Vietnam Red Book.
In Hanoi there are 48 parks and botanical gardens in central districts with the total area of 138 hectares and 377 hectares of grass. In addition, there are thousands of shadowy trees of 67 plant species planted in streets. The system of trees is diverse with 25 popular species, including tamarind, longan, ironwood, etc.
Flower and bonsai villages in Hanoi namely Nghi Tam, Ngoc Ha, Quang Ba, Lang, Nhat Tan, etc., have had long tradition and prestige. Recently, more villages of that kind have been newly formed in suburban districts such as Vinh Tuy, Tay Tuu, Gia Lam, Dong Anh, Soc Son, etc. In addition, many kinds of flowers from the South and overseas have made the biological resource of Hanoi more and more diverse.
1.8. Landscapes
Hanoi 1/300,000 landscape map [2] has been based on natural differentiation principles under natural processes and factors, and the recommended classification includes 6 descending levels: system à subsystem à class à subclass à type à sort [2]. Differentiating features of landscapes in Hanoi are varied but still follow certain principles. In terms of territory, in the North and Northwest, the areas are not very large area, the landscapes are mainly low mountain, high and low hills with bushes, grass patches, cultivated forests, perennial and annual plant societies, dotted with paddy fields. In the Northeast, plains are characterized by paddy fields, perennial and annual plant societies, and cultivated forests. The South and Southeast are low-lying plains, paddy fields in the suburbs surround the city.
Landscape differentiation illustrates the city development history under the influence of natural and anthropological processes. Paddy fields and annual plants account for more than half of 52 landscapes classified. Urban landscape is mainly located in the center with the largest area. Besides, forests and water surface are scatteredly distributed.
Hanoi’s landscape in regional natural conditions presents its distinctive differentiation and its potentials and advantages. In the current development tendency, it is recommended to take full of landscapes in various manners, particularly in developing production and houses.
2. Natural disadvantages to Hanoi’s sustainable development
Environment degradation and natural disasters are two factors seriously affecting the city’s development and life quality of its residents.
2.1. Natural disasters
In order to achieve sustainable development, it is required to identify and acknowledge difficulties and disadvantages of the area, first and foremost natural disasters. Geomorphologic - geologic accident are due to endogenous movements (earthquakes and fractures), or exogenous movements (bank erosion), or human activities (land subsidence), or combination of all mentioned factors (erosion, inundation, etc.). Some basic disasters in Hanoi can be indicated as follows:
· Floods and inundation: Every year, from June to October, water level of the Red River rises, flooding the outer zone of the dike system, even breaking the dikes in some years and causing severe damages both of lives and assets on a large scale. Heavy rains and serious floods causing inundation in Hanoi occurred in 8/1915; 7/1926; 8/1945; 8/1968; 8/1969; 8/1971; 11/1984; 8/1996; 8/2002 and 10/2008.
The urban area is prone to inundation more than ever. In 2001, from 2-4 of August, the rainfall of 200-400 mm caused as many as 120 inundated areas with the depth of 0.2 – 1.1m, leading to congestion in many traffic nodes.
One reason for the city’s constant inundation is that Hanoi has a low topography, especially the south part, which prevents surface water discharge to river systems including the Red River or Nhue-Day. Yet, the major reason is due to human’s wrongdoings including: destroying penetration surface (by concretizing); narrowing and covering detention reservoirs and irrigation systems. Besides, inadequate planning and inefficient implementation have also contributed to the current ineffectiveness of the city’s irrigation system.
· Extreme values of several climatic factors: The lowest temperature in the suburb area can go below 50C, even below 20C, which encourages the formulation of frost in several winter months. Besides, cold waves below 130C lasting in several days also cause damaging colds, particularly in the second half of the winter, heavily affecting residents’ health as well as husbandry and farming.
The highest hourly precipitation is approximately 100 mm and the highest monthly precipitation is about 800 mm, showing a potential of flooding as mentioned.
Strong winds and heavy rains during storms directly affect people’s daily life, production activities and damage houses, electricity systems, water supply and drainage, as well as crop harvests.
· Bank erosion: Riverbank erosion in along the Red River and Duong River occurs not only on unprotected parts but even on protected areas as well. Erosion usually takes place on concave banks on or near fractures [9].
Erosion along the Red River and Duong River is getting more and more serious. It is the consequence of natural factors (modern tectonics, climate changes, etc.) and human activities (i.e. building hydro electronic dams, dikes, occlusion, etc).
· Earthquakes: By 1992, in the lowland area of Hanoi, there have been 152 earthquakes among which two quakes of magnitude 7-8, three of magnitude 7 and 32 of magnitude 6 (MSK-64), the rest was lower quakes [11]. According to construction map and earthquake acceleration for each earth foundation, earthquake magnitude for different types of earth foundation in the urban and suburban areas ranges from 7 to 9.
· Fractures: In Hanoi and the neighborhood, over 70 fractures have been identified. The cracks form ranges of cracks stretching from Northwest to Southeast, identical to deep and reactive fractures during Neotectonic and modern Tectonics. They are believed to result from smooth sliding of earth crust [12].
Fractures appear in residential areas and on the dike system, causing deformation of earth surface, damaging construction and contaminating ground water.
· Ground settlement due to ground water exploitation: Ground water exploitation in Hanoi has begun since the beginning of 20th century and developed rapidly. Research on ground settlement in the city has been conducted since 1988 with the setting of 32 benchmarks. Results show that in 6 years (1998-2004), the exploitation caused the most serious ground settlement in Thanh Cong (47.32mm/ year), followed by Phap Van (23.06mm/year), Ha Dinh (20.57mm/year) [7].
2.2. Environmental pollution
Urbanization and industrialization have been deteriorating environment, air, water, and land quality in Hanoi.
Technology and social infrastructure development is not well corresponding to population growth and urbanization. Water and energy supplying system, drainage system, transportation, and communication network, etc. - all are outdated and badly and poorly concerted, and thus unequal to requirements of environmental services of the city.
The major reason for urban environment degradation is that factors affecting environment have not received proper attention on making plans of using land, managing urban space and designing urban technological infrastructure, etc.
Industrial development plan is obviously inappropriate with environment protection requirements. Urbanization and expansion have led to an awkward situation in which many factories and industrial zones formerly located in the suburb area now lie in densely populated residential areas. Industrial waste has directly affected public health as a result.
Pollution in craft villages is undeniably at alarming level. Techniques and facilities in such villages remain outdated; little waste disposed is properly collected and treated. Production is conducted in the same area with living area, leading to serious surface water, air, solid waste and noise pollution, directly affecting life and health of residents, particularly children, women and the elders.
3. Some recommendations for Hanoi’s sustainable development
3.1. Due attention to environment sustainability in urban construction and development
Urbanization has been of a fast growth on a larger scale, which is indicated by a huge amount of skyscrapers, industrial zones and urban infrastructure systems. In recent years, a series of urban areas have been constructed in a modern style with blocks, villas, green belts and other public buildings such as commercial centers or sports centers, etc. on an area of tens of hectares. Such new urban areas tend to be located in suburbs, mostly in some districts as Tu Liem, Gia Lam, Thanh Tri and so on, in order to reduce the increasingly intense population density of the city centre. Besides, the city has conducted several projects to renovate or reconstruct old and outdated apartment buildings, aiming to create a civilized and modern Hanoi, the capital of Vietnam.
Industrial zones have also been relocated in suburb areas, connecting to surrounding provinces to avoid an awkward situation in 10-20 years when the city expands further and modern industrial zones might be situated in the urban area again. On the other hand, in future, the industrial zones are required to be more comprehensive at a larger scale. The West, Northwest and North of Hanoi’s centre currently are potential areas for mentioned issues, given their stable geological features suitable for construction. Additionally, proper attention has been paid to environmental factors during the construction of industrial zones, say, increasing green areas in the zones. Such parks have also been developed in relationship to new urban areas to ensure accommodation for labor working in the zones.
Together with the development of new urban areas and industrial parks is the establishment of numerous new and modern skyscrapers to be offices or commercial centers for rent in the urban areas. Public construction has also developed. Transportation network has been renovated and expanded, especially the system of overpasses and bridges over the Red River. Infrastructure of the city has constantly been upgraded and improved to be relevant with the development speed of the city.
In general, urban areas and residential areas, existing and under construction, tend to be located to the west – southwest of the city, mostly in the area of Tu Liem province and the north part of Thanh Tri province. Many parts in these areas are unoccupied and have stable geological features suitable for constructing houses.
Obviously, constructions in Hanoi are properly conducted corresponding to site conditions. Suitable areas have been thoroughly selected and planned to establish new urban areas and industrial zones. As for transportation system, expansion has been promoted. Inadequate systems in urban areas have been upgraded. As for those in suburbs, establishment and improvement of the national roads system have been conducted to meet the requirements of Hanoi’s socio-economic development in relationship to other neighboring provinces.
In order to use lands appropriately in the process of urbanization, due attention should be paid to the sustainability of geomorphology-geology against impacts of increasing steady and dynamic load, greater exploitation of resources (water, construction materials) and rising disposal of different kinds of waste. Within the city, based on topographic and geological features of constructions, groundwater, and endogenous and exogenous processes, there are 4 appropriate levels for construction as follows: appropriate, relatively appropriate, inappropriate and unable to construct. Another way is: very good, good, normal and bad. The areas which are considered appropriate for urban development include one between the Red River and Ca Lo River, one between Gia Lam province and communes to the north of Duong River, and others in Tu Liem province, Tay Ho and Cau Giay districts [6]. These areas possess good conditions that can encourage urban development such as rich surface and ground water source, convenient engineering and geological conditions, relative stability and efficient transportation.
3.2. Efficient scenery exploitation and protection
Surrounding Hanoi is a low mountainous area with various unique topographies (caves, waterfalls, cliffs, etc.) and numerous historical and cultural sites which are considered a great advantage to promote eco-tourism and cultural tourism. The West and Southwest parts of Hanoi, say, Ba Vi, Son Tay, Luong Son, My Duc provinces, are suitable for developing tourism centers, resorts and related services. The North and Northeast parts, meanwhile, are appropriate for key industrial - urban zones, regional traffic nodes as well as major tourism centers like Tam Dao, or Soc Son.
Land for cultivation in Hanoi currently still occupies a considerable proportion. However, due to rapid urbanization, there is a shift from cultivated land to land for construction and residential buildings. Soc Son province has the largest area of cultivated land, followed by Dong Anh and Gia Lam province. Yet, in terms of geology and geomorphology, land in Soc Son and Dong Anh is not quite suitable for agriculture. The two provinces have hilly topography with old geological-genetical types, especially a large area of intensively slacked laterite of the deposit in Vinh Phuc. The area of low hills in Soc Son might be appropriate for forestry development to protect eco-balance. Meanwhile, the area of riverside alluvial soil within the city would be suitable for agriculture development.
The area for aquaculture is mainly situated in suburban provinces, mostly in Thanh Tri. Based on Hanoi’s topography, Thanh Tri is the lowest province with a relatively large water area, two factors crucial to the development of aquaculture.
Hanoi for a long time has been regarded as ‘a city of lakes’ embraced by a ‘water frontier’ formed by four former ‘water gates’ namely Buoi, Cau Giay, Dong Lam, Dong Mac gates [10]. Rivers and lakes in Hanoi have actively made contribution to national defense, socio-economic development, and cultural and spiritual life of the capital. Yet, the area for rivers and lakes is decreasing, leading to a loss of beautiful scenery and important functions of the rivers and lakes.
It is essential to comprehensively understand the great value of rivers and lakes and regard them as a factor vital to the city’s development plan. Lakes in Hanoi are supposed to be an invaluable advantage to develop open-air areas, spots for tourism, recreation and sight-seeing. Lake management should be founded on the ecological roles of the lakes. It is also highly recommended to recover their function as a means of rainfall regulation to phase out floods.
Several solutions need to be simultaneously adopted to improve the lake water quality. It is necessary to phase out the discharge of untreated sewage. The process of exchanging water between lakes and the surroundings should be taken into consideration during the lake embankment. More green areas and paths should be established surrounding lakes to prevent waste disposal and lake area exploitation. Moreover, water communication within a lake and among lakes should be encouraged. Using aquatic plants in lake water treatment process is highly recommended.
It is essential to first promote and make full use of lakes as a means of rainfall regulation to prevent floods, and then, conduct basic sewage treatment, and recover lakes’ former functions such as transportation and tourism.
3.3. Natural disaster prevention, waste treatment and environment quality improvement
Obviously, it is required to make comprehensive strategies with short term and long term solutions to natural disasters, especially floods, landslides, and/or ground settlement. Now that the urban topography is relatively low and separated from the Red River by a dike system; that many lakes and ponds are covered and that the city’s surface has been concretized. As for flood and flood risks prevention and mitigation, it is essential to open flows in rivers like To Lich, Day, Set, and Lu; and that capacity of irrigation facilities should be enhanced. Land for construction should be located in accordance with open-air for city expansion. Professional capacity, facilities to provide timing and relevant services, such as tracking, predicting and warning heavy rains and floods, supporting flood and storm prevention management.
Pollution prevention and environment quality improvement should be conducted concertedly with a focus: improving environment-related legal documents; enhancing environment management as well as efficiency of law, regulations on environment; raising administrative bodies and public awareness of environment and environment protection; applying new pollution treatment solutions and methods, especially for water pollution; socializing and increasing investment in disaster prevention and environment protection; integrating environment-related issues into socio-economic development plans and projects; using economic tools and strict sanctions to protect environment effectively; strengthening domestic and international cooperation in environment protection.
Conclusion
Overall, location and natural conditions of Hanoi are considered big advantages to develop a multi-sector economy, encouraging Thang Long – Hanoi to become the most important political, economic and cultural centre of Vietnam. Apart from advantages, natural disasters and environmental pollution have seriously affected the city’s development, particularly in the context of rapid urbanization and inadequate urban management. Sustainable development in the process of world integration should be founded on fundamental regulations on urban development, as well as typical natural and social rules of Hanoi. Given that, viewpoints and recommendations would be introduced comprehensively and concertedly to promote the sustainable development of Hanoi.
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