Nature functions in its own organized system. All development should be in harmony with nature. The ecological balance has to be maintained at all costs. Any step towards development which disturbs the balance and harmony of nature could lead to devastating consequences like landslides, soil erosion, pollution of natural water bodies and atmosphere, silting of rivers, floods and earthquakes.
All human developments should consider and understand the determinants of the natural system. Topography, climate, geology, hydrology and vegetation are the primary determinants of the natural system and they are the prime factors for healthy planning of a city.
Cities that have ignored natural determinants while undertaking developmental measures, are today facing severe environmental crisis. Take the case of the Garden City of Bangalore, which was once considered to be the most habitable city of India is today unable to supply potable water to more than half its population. They have to pump drinking water from fifty kilometers away. This, despite the fact that the city receives ample rainfall and has a number of lakes and tanks to its credit, clearly is a case of bad town planning. Metropolitan coastal cites like Chennai also, which boasts of several natural and man made water channels, that flood during the monsoons have to depend on polluted water sources. Most natural water bodies in Indian urban centers are dry and serve the city as sewage and solid waste disposal sites. Many perennial water sources have depleted into dry seasonal water bodies. The majority of inhabitants in urban centers suffer from respiratory disease and related health disorders. All the above-mentioned facts are the price paid for reckless actions against the natural system, due to a lack of focus and understanding of the natural determinants and cycles of ecological balance.
Apart from understanding the determinants and functioning of the natural systems, utilization and management of the natural resources is another factor to be addressed in planning a city. The uncontrolled utilization of natural resources like water and forests resources at a rate at which the natural system cannot regenerate will lead to depletion of these resources, which would leave the future generations with little natural wealth.
Thus understanding the determinants of the natural system and management of natural resources are two essential components of the Structure Plan preparation for the city of Thimphu.
3.3.1 NATURAL DETERMINANTS OF THIMPHU VALLEY
Topography, climate, geology and surface hydrology are the major determinants creating the basic form of the valley. An understanding of the interrelation between the geological formations, topography and the surface drainage, aids in understanding the basic physiographical zones of the valley. After understanding the basic zones of the valley a study on soil, slopes, aspects, vegetation, fauna and avifauna of the valley determines the interrelationship between the natural determinants.
Analyzing these interrelations of the natural determinants against the prospective land uses determines the land uses suitability of the valley, which is well explained, through a development Suitability Matrix later in this section.
3.3.2 TOPOGRAPHY AND CLIMATE
Thimphu city is located at 27 Degrees, 30 Minutes (N) Latitude and 89 Degrees 30 Minutes (E) in a narrow linear valley of the Wang Chhu. The altitude of the valley ranges from 2248 meters to 2648 meters within the city limits and the surrounding hills range up to 3800 meters. These altitude ranges, categorize the valley between warm temperate (2000 meters – 3000 meters) and cold temperate (3000meters – 3800meters) climatic zones. Altitude ranges, and the climatic zones, determine the habitable zones and vegetation typology for the valley. The Thimphu Chhu or the Wang Chhu and its tributaries cutting across the mountains largely mould the topography of the valley and the surrounding mountains. The eastern ridge of the valley is steep and starts immediately from the riverbed and most of the valley floors occur on the western banks of the river. The slopes of the western ranges are gradual between Dechencholing and Simtokha, predominantly due to the number of streams flowing down to the river. Facilitated by the general north-south orientation of the mountain range, monsoon winds reach the inner Himalayas through the lower valleys, which provide a passage for the moist winds. Rainfall is not evenly distributed in the valley. Mountain ranges stand in the way of approaching moist winds, creating windward and leeward sides. Thimphu Valley lies in the leeward side of the mountains and the valley area is relatively dry, and has a distinctively different type of vegetation than the windward side. Hence Thimphu Valley is covered with coniferous trees, which require less moisture. Broad-leaved trees dominate the windward side of Punakha.
The city part of the valley enjoys
a warm, temperate climate with an average rainfall of 500 to 1000 mm. The Average
daily winter temperature varies between 5 deg C to 15 deg C and the average
daily temperature during summer varies between 15 deg C to 30 deg C. The southwest
monsoon brings rainfall to the valley during the month’s mid-June to September.
The rainfall is marked with lightning and thunder, cumulus-nimbus clouds and
light showers dominate the weather. Rainfall in this region can continue for
several days causing landslides along roads. Streams and rivers swell up carrying
huge amounts of debris from forests. Deep puddles, thick mud, and landslides
along roads form barriers to transportation. Cold winds, low temperatures at
night, and moderate temperatures during the day, cloudiness, light showers and
snowfall mark winter weather in this zone. Fog causes poor visibility, which
poses a threat to vehicular traffic. As spring approaches, the landscape is
marked by violent winds and relatively dry and clear skies.