Major Engineering Geological Problems and Hazards in Nepal
The major tectonic divisions of Nepal viz. Indo-Gangetic Plains, Siwaliks, Lesser Himalaya, Higher Himalaya and Tethys Himalaya have different kinds of engineering geological problems:
· During construction of civil structures in Terai (Indo-Gangetic plain), the engineering geological problem which may arise will be associated with its unconsolidated sediments. The river deposit of Terai may suffer settlement and liquefaction during earthquakes or simply over time. The soils have low bearing capacity hence infrastructures should be designed considering these factors.
· The Terai region is prone to floods every year. The low gradient flat land and large rivers are the main cause of floods every monsoon. The projects in Terai should be aware of the flood hazards occurring almost every year.
· The Siwlaik region is the young sedimentary rock sequence of the Nepal Himalaya. The immature and fragile topography owing to alternating hard and soft rocks, seasonal rivers and geological structures make this area prone to soil erosion and mass movements. These hazards often result in halt of traffic due to damaged highways and difficulty in construction of infrastructures.
· The Lesser Himalaya with its variation in topography and geological condition is frequently afflicted by landslides, soil erosion and toe cutting by high gradient rivers. The southern slopes of the Lesser Himalaya receive more rainfall and more sunlight causing rapid weathering and erosion of these slopes resulting mass wasting.
· The Higher Himalaya of Nepal is known for rock falls and GLOF hazards. The presence of hard crystalline metamorphic rocks with adverse orientation and many glacial lakes, these both hazards pose a serious threat in projects both running and under construction.
· Tethys Himalaya is the rain shadow area of Nepal where landslides are rare due to lack of water. The main hazard is the soil erosion due to high wind. The rocks are sedimentary and their weathering produces fragile hills of unconsolidated sediments. The rare rainfall in these regions may cause flash floods and debris avalanches due to this unconsolidated soil mass.
Importance of the Engineering Geological Studies in Nepal
The Himalayan Range, the highest and the youngest mountain range in the world, is very fragile and delicate. Owing to the inherent geological, physiographic and climatic conditions, as well as recent excessive human interventions, the Himalayan region is quite vulnerable to mass movements, floods and earthquakes. These natural hazards make it a highly difficult place for infrastructure development and maintenance. About 83% of Nepal lies in this mountainous terrain.
Highly dynamic physical processes dominate the mountainous terrain of Nepal, and therefore, implementing infrastructure development projects is a challenge. Construction, maintenance and rehabilitation of infrastructure under the unique Himalayan condition require innovative and more pragmatic approach compared to less critical terrains in other parts of the world. Many earlier projects have faced various problems during survey, design and construction phases, and in the process invaluable experience has been gained during the last five decades. New concepts, approaches and techniques appropriate to this unique Himalayan terrain are gradually emerging. These techniques and experience are important and far reaching, and may be applicable in similar regions of the developing world. Over the years Nepal has gained a significant amount of experience in landslide studies and stabilization, survey, design and construction of roads, tunnels and dams; in the fields of hazard and risk assessment, low cost road (green road) engineering; and bio engineering. Infrastructure development in the Nepalese Himalayan region is a formidable task with considerable problems caused by washouts and failures resulting from floods, erosion, gullying and landslides. The combination of inherently weak geological characteristics and the strong south Asian monsoon rains make the Himalaya fundamentally one of the most fragile and delicate mountain ranges of the world. As a result, the mountains are highly vulnerable to landslides and other mass wasting processes.
The success and failure of the last five decades of engineering practices in Nepal need to be seriously anlayzed and lessons learnt must be carried forwards for the future projects.
Gradually, realizing the importance of the engineering geological study in a mountainous country like Nepal, such studies were extended also to other infrastructure development.
The major tectonic divisions of Nepal viz. Indo-Gangetic Plains, Siwaliks, Lesser Himalaya, Higher Himalaya and Tethys Himalaya have different kinds of engineering geological problems:
· During construction of civil structures in Terai (Indo-Gangetic plain), the engineering geological problem which may arise will be associated with its unconsolidated sediments. The river deposit of Terai may suffer settlement and liquefaction during earthquakes or simply over time. The soils have low bearing capacity hence infrastructures should be designed considering these factors.
· The Terai region is prone to floods every year. The low gradient flat land and large rivers are the main cause of floods every monsoon. The projects in Terai should be aware of the flood hazards occurring almost every year.
· The Siwlaik region is the young sedimentary rock sequence of the Nepal Himalaya. The immature and fragile topography owing to alternating hard and soft rocks, seasonal rivers and geological structures make this area prone to soil erosion and mass movements. These hazards often result in halt of traffic due to damaged highways and difficulty in construction of infrastructures.
· The Lesser Himalaya with its variation in topography and geological condition is frequently afflicted by landslides, soil erosion and toe cutting by high gradient rivers. The southern slopes of the Lesser Himalaya receive more rainfall and more sunlight causing rapid weathering and erosion of these slopes resulting mass wasting.
· The Higher Himalaya of Nepal is known for rock falls and GLOF hazards. The presence of hard crystalline metamorphic rocks with adverse orientation and many glacial lakes, these both hazards pose a serious threat in projects both running and under construction.
· Tethys Himalaya is the rain shadow area of Nepal where landslides are rare due to lack of water. The main hazard is the soil erosion due to high wind. The rocks are sedimentary and their weathering produces fragile hills of unconsolidated sediments. The rare rainfall in these regions may cause flash floods and debris avalanches due to this unconsolidated soil mass.
Importance of the Engineering Geological Studies in Nepal
The Himalayan Range, the highest and the youngest mountain range in the world, is very fragile and delicate. Owing to the inherent geological, physiographic and climatic conditions, as well as recent excessive human interventions, the Himalayan region is quite vulnerable to mass movements, floods and earthquakes. These natural hazards make it a highly difficult place for infrastructure development and maintenance. About 83% of Nepal lies in this mountainous terrain.
Highly dynamic physical processes dominate the mountainous terrain of Nepal, and therefore, implementing infrastructure development projects is a challenge. Construction, maintenance and rehabilitation of infrastructure under the unique Himalayan condition require innovative and more pragmatic approach compared to less critical terrains in other parts of the world. Many earlier projects have faced various problems during survey, design and construction phases, and in the process invaluable experience has been gained during the last five decades. New concepts, approaches and techniques appropriate to this unique Himalayan terrain are gradually emerging. These techniques and experience are important and far reaching, and may be applicable in similar regions of the developing world. Over the years Nepal has gained a significant amount of experience in landslide studies and stabilization, survey, design and construction of roads, tunnels and dams; in the fields of hazard and risk assessment, low cost road (green road) engineering; and bio engineering. Infrastructure development in the Nepalese Himalayan region is a formidable task with considerable problems caused by washouts and failures resulting from floods, erosion, gullying and landslides. The combination of inherently weak geological characteristics and the strong south Asian monsoon rains make the Himalaya fundamentally one of the most fragile and delicate mountain ranges of the world. As a result, the mountains are highly vulnerable to landslides and other mass wasting processes.
The success and failure of the last five decades of engineering practices in Nepal need to be seriously anlayzed and lessons learnt must be carried forwards for the future projects.
Gradually, realizing the importance of the engineering geological study in a mountainous country like Nepal, such studies were extended also to other infrastructure development.