Explain why the Himalayas is naturally active in terms of geomorphological processes.
The Himalayas is a mountain range in Asia that lies between the Indian subcontinent and the Tibetan Plateau. Its formation began around 45 million years ago and continues up until now. The Indo-Australian plate is moving into the Asian plate and the Himalayas is rising about 5 mm per year. Because of the plate movement the region of Himalayas is also seismically active. Along with the earthquakes, such natural hazards as floods, landslides, and erosions also happen in the Himalayas.
There are about 15000 glaciers on the Himalayan range, many of which are declining in size. The higher parts of the mountain range are covered with snow all year long. The snow as well as some of the glaciers melt and the water flows into several rivers, most of which compose two large basins: the Indus Basin the Ganges-Brahmaputra Basin.
Rainstorms and snow melts cause floods in the Himalayas. Sub-tropical climate together with high and steep landscapes and weakened rocks are responsible for landslide and erosion. Active tectonics cause many landslides, which occur nearly everywhere in the Himalayas. One of these events can cause a chain reaction. For example, an earthquake or heavy rainstorms can trigger a landslide; a landslide can block a river, create a dam, which will lead to a flood.
Explain how human activities have affected the rates of geomorphological processes in the Himalayas.
Deforestation is one of the main ways men can affect geomorphological processes. It causes soil erosion, degradation, and other negative effects. Some experts argue, that badly-run farming, terracing, deforestation of the Himalayas, and road construction have had impact on slope stability and lead to erosion and flooding. There is no doubt that human population has increased dramatically and the use of land has changed in the Himalayas over the recent decades. However, whether human activities really cause landsliding and floods is still debated. The region has always suffered from floods, however, it is possible that human intervention has made the situation only worse and has caused back-flooding. In addition to that, Himalayas’ forests have been cut down starting in the 1950s, which has caused, as some studies say, additional floods, landslides, and erosions.
Forests are able to absorb some of the heavy rains which fall during the monsoon seasons. Without forests, water rushes down taking soil with it. Much of the forests in the Himalayas were cut down in order to clear the land for agriculture, however, these agricultural lands have not been maintained properly. In the Himalayas, people use lands for agriculture for several years until the land stops being fertile, then move to another piece of land.
Some scientists point out, that due to deforestation, less water is stored underground. Because of human intervention sediment is redistributed downwards. It is possible that deforestation also causes drying of rivers and soil erosion.
Describe and suggest reasons why human impact varies.
Human activities affect mainly areas in the foothills of the Himalayas. There are some man-induced changes in the Himalayas on micro level, for example, in local watersheds. On large scale, it is more difficult to prove that there is correlation between what people are doing in the mountains and floods, erosions, landslides, etc.
The higher in the mountains the smaller the density of the population, and accordingly, there is less impact on the nature. People live mainly on the foothills of the mountain range. Hill-terracing, agriculture, and deforestation have definitely left their impact on the area. The changes have been noticed only close to the roads (slope degradation) and places where people live. In central Himalayas very few changes have been recorded.
Building of roads often causes landslides. Deforested catchments erode faster than they would otherwise. The land used for agriculture often becomes infertile soon and then is left without any vegetation. It is also possible to argue that human impact can be traced to the increased temperatures and melting of the glaciers, however, such effects are more difficult to trace and their impact also varies spatially.
Wu and Thornes, for example, state that hill terracing has positive rather than negative impact on the mountains. Moreover, some scientists agree that the power of nature is so much stronger than that of humans, that men could hardly have any significant impact on the natural processes in the Himalayas.
To what extent do you think deforestation in the Himalayas is a cause of flooding in Bangladesh?
The flooding in Bangladesh is not caused solely by human actions. The region has always had heavy seasonal rainstorms, landslides, and erosions caused by nature. The Himalayas has experienced rapid population growth over the last several decades, as a result, there have been changes in the land use and many forests have been destroyed. Previously, people living in the Himalayas have been blamed for the increased floods in Bangladesh, however, this opinion has been increasingly rejected and many experts point out that people cannot be solely responsible for the disastrous floods. Several studies have showed that processes in the Himalayas are not important for the floods in Bangladesh.
The level of flooding in Bangladesh does not seem to be correlated with what’s going on in the mountains. For example, during the years of most dangerous floods in Bangladesh the potential runoff from the Himalayas was below average. Moreover, when a flood originates high in the mountains it tends to level on its way to the lowland. Devastating floods have always occurred in Bangladesh and there is no evidence to believe that the situation has significantly changed in the last decades – both the magnitude and the frequency of floods in Bangladesh stayed approximately the same over the last 100 years. It is possible to suggest that climate change and global warning have an effect of floods and landslides.
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Works Cited
Champati Ray, P.K. and Joshi, D. D. “The Effect of Climate Change on Geomorphic Processes and Landslide Occurrences in Himalaya.” 2008. Retrieved from: http://saarc-sdmc.nic.in/pdf/publications/climate/chapter-5.pdf.
Hearn, G. J. and Lawrance, C. J. “Geomorphological Processes in Eastern Nepal as a Basis for Road Design.” 2000. Retrieved from: http://www.transport-links.org/transport_links/filearea/documentstore/221_Geomorphological%20processes%20in%20eastern%20Nepal%20as%20a%20basis%20for%20road%20design.pdf.
Hofer, Thomas. “What Are the Impacts of Deforestation in the Himalayas on Flooding in the Lowlands? Rethinking an Old Paradigm.” Retrieved from: http://www.fao.org/forestry/11721-05efcd431f314dec54fa94ae15aa32a82.pdf.
Food and Agriculture Organization of the United Nations. “Himalayan deforestation and downstream floods.” 2007. Retrieved from: http://www.fao.org/forestry/37244/en/.
