3.9 ECOLOGICALLY FRAGILE AREAS

A discerning study and analysis of all natural determinants of the valley has revealed the various environmental zones of the valley. By the process of overlaying all the maps and analyzing other related information we can identify the most sensitive environments within the valley. These must be preserved.

The map on ecologically fragile zones shows the most sensitive environments, which have to be protected, conserved and managed.

The identified zones are the Forests, Marshlands, Riparian Zones, Lower River Terraces and the areas with 30% slopes and above.

All the above-mentioned zones within Municipal Corporation limits are facing severe threats from uncontrolled growth. Forest lands are getting cleared and encroached upon for urban uses. The Riparian Zones have been totally destroyed along most of the river, and stream stretches, within the City Core area. These streams and rivulets act as sewage drains. Marshlands are either garbage disposal sites, or are taken up for urban activities. Barren, steep slopes are carved out for roads without stabilizing the topsoil. The Lower River Terraces are in demand for industries and residential land uses.

Development is inevitable and must be accommodated. However uncontrolled growth is destructive. Conservation principles can avert destruction, and can ensure enhancement of the city’s environment.

These zones are the functional centers of the natural systems. Suitable land uses for these zones can be identified through development suitability analysis using a “Suitability Matrix.” Such a matrix and its description and use is presented here in the report.

A road construction on barren hill slopes which are above 30% slope.


A construction site within the Riparian Zone of Wang Chhu near Dechencholing


Sewage and Solid Waste Pollute the Wang Chhu and it’s tributaries

MAP NO. 3.10 FRAGILE ECOLOGICAL AREAS(Click to view the map)


3.10 DEVELOPMENT SUITABILITY MATRIX

The Suitability Matrix is a comprehensive chart, which determines the levels of inter-compatibility between urban land uses and the natural / environmental determinants. Here each land use was tested against all others to determine compatibility and incompatibility. This is an attempt to seek multiple compatible land uses, rather than a single optimum land use. For example, an area suitable for agriculture could support orchards, recreational land uses, farmhouses and other agro-based land uses, but may not support industries and mining, thus determining the compatible and incompatible land uses of the same area.

The second matrix is between the land uses and the environmental determinants, which identifies the resources necessary for the prospective land uses, and also determines the permitted level of interaction between the land use and natural determinants.

For example, agriculture requires a flat terrain and rich soil, so the best suitable natural determinants are flat to gradual slopes (0-10%), and Lower River Terraces (geological determinants). The incompatible determinants are steep slopes, fog and snow sensitive climatic regions.

Urbanization requires flat and gradual slopes (0-10% slopes), but it is not suitable in areas above 30% slopes. Apple orchards require slopes in the range of 20-30 %, and are not suitable at very steep slopes.

The third matrix shows the consequences and impacts, which will arise due to the prospective land uses. For example, industrial land uses will cause air, water and noise pollution. Development on steep slopes will cause soil erosion and landslides.

The overall outcome of the matrix determines that the Alluvial Fan Deposits of the valley floor are the most suitable areas for prospective urban land uses, while the Lower River Terraces of the valley are most suitable for recreation, and the forest areas are most suitable as wilderness preserves.

This matrix allows us to plan, utilize and manage the valley with an understanding of nature and how we can live in harmony with the environment.

Applying the results of this Development Suitability Matrix to land use planning in Thimphu Valley results in balanced development between urbanization and the natural and environmental determinants, thus harmonizing the development with the natural system.

TABLE 3.5: DEVELOPMENT SUITABILITY MATRIX(Click to vie the Table)