What is a landslide?
- Landslide is a physical phenomenon when a part of rock, and/or debris/ soil fall due to the action of gravity.
- It is caused by a set of terrain-specific geofactors (e.g., slope, lithology, rock structure, land use/ cover, geomorphology etc.) and in general is triggered by heavy rainfall or earthquake tremors.
- In Indian terrain, landslide events are mostly triggered by monsoonal rainfall but examples of earthquake-triggered landslide is also not uncommon in India (e.g., Uttarkashi Earthquake, Chamoli Earthquake, Sikkim Earthquake etc)
Which part of India is landslide-prone?
- The entire Himalayan tract, hills/ mountains in sub-Himalayan terrains of North-east India, Western Ghats, the Nilgiris in Tamil Nadu Konkan areas are landslide-prone (~ 0.42 Million Sq. Km.; including the permafrost regions it becomes 0.49 Million Sq. Km)
What is landslide inventory?
- Each landslide has a specific spatial and temporal attributes. GIS is the only tool through which it’s spatial, temporal and other attributes can be linked and be kept in a georeferenced spatial database.
- Landslides are also of varied types, involving different types of material, different types of movement etc.
- Apart from the above, a lot of spatially-associated attributes about its causal geofactors can also be observed which can be linked to a landslide incidence.
- All the above information in such a georeferenced spatial database (e.g., GIS) can exhibit the landslide inventory of an area.
What is landslide susceptibility analysis?
- Techniques to predict spatial locations of future landslide occurrences. That mean it answers where a future landslide can occur.
- This requires prior knowledge about the landslides that occurred in any area.
What is landslide hazard analysis?
- Techniques to predict both spatially and temporally the locations of future landslide occurrences of certain magnitudes. This means that this predictive analysis answers where, when and how large the future landslide could be.
- For landslide hazard analysis, availability of historical information on past landslides is essential.
What is landslide risk analysis?
- Techniques to predict or estimate monetary losses caused to an element-at-risk (roads, buildings) or estimation of losses to human lives due to any landslide hazard. This is the ultimate aim of any landslide hazard studies and mostly be useful to planners and insurance agencies.
- However, the above analysis is extremely difficult due to non-availability of both spatial and temporal information of landslide occurrences.
- Like many landslide-prone countries, India is also having the similar problems. That is why landslide hazard and risk analysis in truest sense are rare in India.
- To remedy the above and to prepare a dynamic, and spatially-distributed national landslide repository, the Web based National Landslide Incidence Inventory project of GSI has been taken up which will ultimately prepare a comprehensive nation-wide landslide database.
What is Landslide Risk Management?
- It is the whole gamut of exercise in landslide studies starting from identification of a landslide-related problem, knowing its susceptibility (predictions of spatial locations), hazard (combination of spatial, temporal and magnitude predictions) and estimation of risk (loss estimation), followed by risk evaluation and process to define and implement ground-level actions towards reduction of the risk.
What is the main role of GSI in the landslide risk management?
Scientifically GSI's main role or position in the Landslide Management Framework is as follows.
From the Landslide management Framework, it is clear that GSI acts the most fundamental and pivotal role in the overall Landslide Risk Management Framework i.e. analysis of landslide hazard. GSI can partly contribute in Landslide Risk Analysis but as far as risk analysis in totality is concerned, role of social scientists, engineers and planners are also required.
Describe the specific roles of GSI in the landslide risk management
Pre-disaster landslide management
- Landslide Susceptibility/Hazard Mapping
- Rainfall based threshold analysis and early warning (work on experimental mode is in progress)
- Risk analysis (Work on experimental mode has been attempted)
- Instrument-based landslide monitoring and early warning (a project with Defence Terrain Research Laboratory has taken up which will be operational on ground w.e.f. FS 2015-16)
Post-disaster landslide management
- Landslide Inventory Mapping
- Site-specific landslide monitoring and detailed mapping
- Assessment of safe route
- Suggesting both short-term and long-term remedial measures for site-specific landslides.
- Monitoring of some conspicuous landslides.
Landslide Hazard Information Management
- Web based landslide incidence inventory map service
- Organising Workshops, Seminars and Awareness Programmes
Coordination and Cooperation
- To maintain a close liaison with the National Disaster Management Authority (NDMA), Ministry of Home Affairs (MHA), Central and State Government agencies and to coordinate and facilitate implementation of landslide Disaster Management (DM) programmes through the NDMA.
- Played a pivotal role in framing the Landslide and Avalanche Guidelines of NDMA (2009).
- Organising Contact Programmes.
- Organising Landslide Workshops/ Seminars.
- All sorts of technical assistance to Ministry of Mines, Govt of India, Technical Advisory Committee (TAC), State Governments, local authorities on all sorts of landslide related issues etc.
- Created an exclusive Cell for Geohazards Research & Management (GHRM) under the direct supervision of DG, GSI. This Specialised Cell is being engaged in GSI in augmenting the expertise in the field of landslide research and managing all sorts of landslide activities/ programmes of GSI, assisting DG, GSI in coordinating with all stakeholders on matters related to landslide hazards etc.
When India can have such full-fledged web-based map service in a GIS platform?
- GSI is already having the database structure prepared with a provision of storing as many as 41 different attributes per landslide incidences, which is currently operational and anybody can access about 281 such data in GSI Portal.
- GSI has taken up Region-wise compilation programme at its Geohazards Research & Management Cell, Kolkata with an aim to update a substantial inventory data in the portal by March 31, 2016 (the amount could be additional 2000 landslide incidences).
- The web-based inventory will also have spatial locations of all the landslides that are being mapped in the on-going National Landslide Susceptibility Mapping (NLSM) programme of GSI which is expected to collate/ map thousands of landslides in different landslide-prone areas. The NLSM Project envisages completing its target of seamless landslide susceptibility map generation of the entire 0.42 Million sq. km landslide-prone areas in India by March 31, 2020.
- All the major and prominent landslides will be linked with maximum number of ancillary attributes (max. 41 attributes).
Whether any work on landslide early warning has been done by GSI?
- GSI has recently signed an MOU with Defense Terrain Research Laboratory (DTRL) - a DRDO Organization for an instrument-based landslide monitoring and early warning project in Uttarakhand. The project is of 3 years and will initiate w.e.f. FS 2015 - 16.
What kind of preventive and remedial measures are being taken by Govt. of India to minimize damages caused by landslides?
- As per the Disaster Management Act 2005, the Union Government is engaged more in strengthening nation' s preparedness to prevent any hazard rather that stressing more on relief and rehabilitation.
- In this line, the task of multi - scale landslide hazard zonation is an important geo - information tool to the planners and administrators to minimize such losses due to any landslide hazard.
- To accomplish this target, the nodal Ministry/ Department - MOM / GSI has taken up NLSM Programme to complete macro-scale (1:50,000) landslide susceptibility mapping of the entire landslide prone areas of India in a planned manner which are likely to be completed by 2020.
- Similar studies on meso (1:10,000) and micro (1:2000/1000) scale at specific problematic sites are also being taken up by GSI as per the requests received from the State Governments and Road Maintaining Authorities.
- Off late GSI has also embarked on taking up projects on landslide monitoring and early warning (e.g., GSI - DTRL Collaboration).
- GSI, being the nodal agency is engaged in conducting awareness programmes, workshops in different landslide - prone Regions. In this year, one such awareness programme was held in Kerala.