Note4Students

From UPSC perspective, the following things are important :

Prelims level: Land Subsidence

Mains level: Read the attached story

joshimath

Many families living in Uttarakhand’s Joshimath has shifted to safe places after their homes developed deep cracks, leaving them in a panicked state.

Joshimath Crisis

Joshimath lies on an ancient landslide, resting on a deposit of sand and stone, not rock.
The rivers Alaknanda and Dhauli Ganga play their part in triggering landslides, by eroding the river banks and mountain edges.
It is believed that increased construction activity and growing population have contributed to frequent landslides in the area, the 1976 Mishra Committee Report had pointed out.

What is Land Subsidence?

Land subsidence is when the ground sinks or settles.
It can happen because people are taking too much water or minerals from the ground, which causes the ground to sink.
It can also be caused by natural processes, like soil compaction or the movement of the earth’s crust.
Land subsidence can cause problems like damage to buildings and roads, and can make it more likely for flooding to occur.

Joshimath is a deposit of sand and stone — it is not the main rock — hence it was not suitable for a township.
Vibrations produced by blasting, heavy traffic, etc. has led to a disequilibrium in natural factors.
Lack of proper drainage facilities also leads to landslides.
A lot of water has been percolating down into the porous crystalline rocks beneath the surface, softening them further.
When water is not allowed to flow down its natural course, it creates a lot of pressure, either over the ground, or underneath.
The existence of soak pits, which allow water to slowly soak into the ground, is responsible for the creation of cavities between the soil and the boulders.
This leads to water seepage and soil erosion.

Overt tourism: The place is now the hub of tourists headed to at least three important shrines — Badrinath, Hemkund Sahib and Shankaracharya temple — as a result of which major infrastructure development has taken place.
Ignoring topography: There are lots of loose soft rocks, moraine (material left behind by retreating glaciers), and sediments. The soil is, therefore, not ideal for large constructions.
Seismically active area: Added to this is the fact that the area falls in a highly seismic zone, and experiences regular tremors, making the top soil unstable.

1976 Mishra Committee Report suggested-

Imposition of restrictions on heavy construction: Construction should only be allowed after examining the load-bearing capacity of the soil and the stability of the site, and restrictions should also be imposed on the excavation of slopes.
Keeping the boulders: In the landslide areas, stones and boulders should not be removed from the bottom of the hill as it would remove toe support, increasing the possibility of landslides.
Sealing of cracks: Cracks which have developed on the slopes should be sealed. The toe of a landslide is its bottom-most point.
Conserving of trees: It has also advised against cutting trees in the landslide zone, and said that extensive plantation work should be undertaken in the area, particularly between Marwari and Joshimath, to conserve soil and water resources.
Agriculture on the slopes must be avoided: Activities like ploughing loosens the soil thereby triggering the scope for landslides.
Preventing water seepage: To prevent any more landslides in the future, the seepage of open rain water must be stopped by the construction of a pucca drainage system.
Cobbled roads: Roads should be metalled and without scuppers, that drain away the water from the road surface.
River training: The construction of structures to guide the river’s flow should be carried out. Hanging boulders on the foothills should be provided with appropriate support.

Ensuring safety of people: This should be immediate priority. State government should establish a clear and continuous communication channel with the affected people.
Time-bound reconstruction plan must be prepared.
Continuous seismic monitoring must be done.
A risk sensitive urban development plan for Joshimath should also be developed.