“GSI has simply accomplished a macro scale landslide susceptibility mapping in 2020 for all the landslide-prone areas of 19,300 sq. km. in components of 13 districts of Kerala”
“A regional land use planning might be began instantly in Kerala with the obtainable macro-scale landslide geo database to scale back the chance to a terrific extent,” says Dr. Saibal Ghosh, Director (Geology), Geohazard Analysis and Administration Centre, Geological Survey of India (GSI), in an e-mail interview to The Hindu because the State continued to face the rising risk of disasters induced by landslide occasions.
With landslides on the rise in Kerala following excessive climate occasions, is it not time for the State to make land use zoning regulation necessary?
In hilly/ mountainous terrains, it’s potential to know or map areas with various levels/ probability of susceptibility to initiation of landslides or comparable mass losing processes, which might act as an important geo data instrument to be used in land-use zoning rules. Nonetheless, the provision of that specific spatial geo data and its scale of mapping is essential to the planners and directors for implementation.
GSI has simply accomplished a macro scale (1:50,000) landslide susceptibility mapping in 2020 for all the landslide-prone areas of 19,300 sq. km. in components of 13 districts of Kerala. Whereas making ready the landslide susceptibility map, GSI has additionally collected field-based information of 1395 nos. of landslide incidences. The above spatial geo data on a 1:50,000 scale can be utilized for regional planning functions of land use zoning rules. Nonetheless, for the implementation of local-scale land-use zoning rules in a extra particular manner on a smaller space, bigger scale (not less than 1:10,000 or bigger) landslide susceptibility or hazard maps are required.
Now after finishing the nation-wide baseline information era process on the 1:50,000 scale, GSI, in session with the State governments involved is stressing extra on finishing up mesoscale (1:10,000) landslide susceptibility mapping in essential sectors in all of the landslide-prone states within the nation, together with Kerala. GSI has a perspective plan to cowl about 200 such essential sectors on a 1:10,000 scale by the following 4-5 years in India. I feel with all of the above instruments collectively, possible land-use zoning must be tried within the fragile hilly/ mountainous terrains sooner or later in all of the landslide-prone States.
What are the teachings learnt from the GSI’s landslide susceptibility mapping programme carried out in Kerala?
Spatial areas with the various probability of susceptibility to landslide initiation (Low, Average, and Excessive) on a baseline macro-scale (1:50,000) at the moment are delineated and recognized. The distribution of historic landslides can be recognized, which provides a proxy to the prevalent landslide susceptibility situations in an space. Nonetheless, this stock is getting up to date yearly with the prevalence of recent/ recent landslides within the State.
The macro-scale (1:50,000) landslide susceptibility mapping supplies a superb baseline geoinformation instrument for understanding landslide situations over a regional space. This additionally facilitates the identification of essential areas for taking on upscaled (1:10,000/ 1000) research additional.
Additionally it is necessary to notice that, the traditional landslide susceptibility maps can solely mannequin the zone of initiation or supply areas of any future landslide, and this can be a systemic limitation of any landslide susceptibility mannequin; nevertheless, like different areas, and in Kerala too, many damages have been observed due to linear particles flows, the place comparatively secure slopes within the landslide runout and/ or accumulation zone, situated a lot away from the supply areas additionally turn out to be severely hazardous/ deadly, and thus have to be modeled too to understand the whole hazard state of affairs in an space, which isn’t solely tough but in addition may be very difficult too. That’s the reason, in mesoscale (1:10000) landslide susceptibility mapping, GSI can be making an attempt particles stream runout influence mannequin outputs within the landslide susceptibility mannequin to make it extra inclusive, applicable, and helpful at that bigger scale.
Landslide susceptibility fashions are developed utilizing rated and weighted pre-disposing geofactor maps that are principally static in nature, however landslides are in the end triggered by some dynamic triggering issue (e.g., rainfall, earthquake). In India, landslides are predominantly triggered by rainfall, occurring principally throughout the monsoon interval. In any terrain, the triggering of a landslide is determined by the terrain-specific rainfall threshold. If these particular areas out of the blue obtain a particularly excessive quantity of intense rainfall, which is far greater than the native rainfall thresholds, there might be the possibilities of prevalence of maximum landslide occasions in that space, and which will closely transgress into the average, and even low vulnerable areas too. In India, in lots of landslide-prone States in latest occasions, the identical has been skilled typically, the place the triggering rainfall was 5-10 occasions greater than the traditional peak monsoon rainfall depth of that particular space, and that triggered extreme damages by rockfall, slides, and flows, even in low to average areas. This explicit excessive state of affairs may be very tough to mannequin.
The short-term and long-term options for the State to keep away from such disasters sooner or later?
Landslides are pure phenomena, and the identical can not often be averted in hills/ mountains. What we are able to do is to scale back its threat to a terrific extent by implementing the next duties in a deliberate phase-wise method.
Land-use zoning rules are required in Indian hills/ mountains, and for which all of the obtainable scientific information must be used. This must be applied phase-wise by prioritising probably the most weak districts and sectors within the State (each brief and long run).
In every district of the State, all of the essential sectors for mesoscale (1:10,000) landslide susceptibility and hazard mapping, and important landslides for site-specific remediation have to be recognized for planning and prioritising landslide remediation, mitigation, and administration work (brief time period)
To take up complete landslide mitigation and administration, some pilot districts within the State are to be recognized first; and a complete mitigation technique for these districts be deliberate and applied by making an allowance for all of the obtainable scientific information/ data; if new information is to be generated, the identical could also be prioritized to be used; association for unique funding association for such mitigation duties be made beforehand in a DPR mode; execution of mitigation work additionally must be monitored intently by an professional group (each brief and long run). The recognized pilot district be made a mannequin district for implementing complete landslide mitigation and administration duties.
Simultaneous implementation of regional rainfall threshold-based landslide early warning system, and site-specific landslide early warning system utilizing in-situ devices for just a few essential landslides within the pilot district be deliberate and applied within the recognized pilot district too (each brief and long run).
Landslides severely have an effect on the neighborhood, and they’re the first-level responders. Any related endeavour for landslide catastrophe threat discount (DRR) thus requires the involvement of the neighborhood proper from the starting stage. Subsequently, any measures deliberate to be applied must be designed and executed by involving the native stakeholders, and the neighborhood from the very starting in order that their understanding of landslide dangers, their capability, and resilience are improved altogether, to realize an acceptable landslide DRR in that space.