Strategy for landslide risk reduction

Devastating landslides in the Dima Hasao district in Assam disrupting road and railway communication and claiming several lives have exposed critical gaps in landslide disaster risk reduction in the state. A catastrophe is waiting to happen if urgent measures are not initiated for stabilization and mitigation of landslides in the hill district as well as other areas of the northeast region. The National Landslide Risk Management Strategy formulated by the National Disaster Management Authority lays down the basic framework of landslide risk management, but the scale of devastation is a pointer that effective application of the strategy is not yet visible. The document highlights north-eastern states being vulnerable to landslides due to fragile geology, active tectonics, high relief, critical slopes, intense rainfall as well as anthropogenic activities at various locations of these states. The region falls in seismic zone V amplifies the risks in landslide zones. One of the gaps listed in the strategy document is slope cutting and blasting activity for construction and widening of hill roads are triggering many landslides, which are in many cases merely 10-30 metres wide. "Such small landslides are often life-threatening on hill roads and are difficult to depict on 1:50,000 scale LSZ (Landslide Susceptibility Zonation) maps," it states. It also points out that landslide zoning maps so far available in India are mostly LSZ maps. However, in most cases, they are termed Landslide Hazard Zonation (LHZ) maps despite not having any connotation about the magnitude and predicting the time of occurrence of a landslide. The NDMA strategy lists several other gaps addressing which are crucial for correct risk analysis and undertaking effective risk mitigation. Non-availability of Landslide Susceptibility Management (LSM) maps, for all areas for which LSZ maps are available, is one such gap, it states, and adds that even the available LSM maps are lacking site-specific structural and non-structural mitigation measures since most of such LSZ maps are on 1:50,000 scale. Besides, most of the existing LSZ and LSM maps are lacking administrative boundaries such as district, Tehsil, block and village boundaries superposed on hazard zones. "The available LSM maps address the anthropogenic intervention (in landslide-susceptible zones) very casually by suggesting measures such as "avoid further construction" etc. This makes it difficult for the authorities to ensure strict adherence to land use regulations such as a complete ban on construction activity in a landslide hazard-prone area", states that document. It also mentions that the mitigation measures recommended in the existing LSM maps are generalized ones, such as "afforestation" and "biotechnical measures" without any mention of the particular varieties of the fast-growing trees and useful grasses to be grown or a list of biotechnical measures to be taken for stabilizing the hill slope. Existing LHM maps do not address the crucial aspects of overloading and or undercutting of hill slope due to anthropogenic activities and therefore, provide no clear guidelines for removal of those manmade constructions in particular which are overloading or undercutting the hill slope or blocking, diverting or narrowing the natural drainage courses, the strategy paper explains which warrants the attention of the Central and the State governments in the region. Harping on the need for the development of landslide monitoring and early warning system, the national strategy emphasizes exploring two triggering factors – rainfall and seismicity for sounding an early warning. Landslides are often triggered by intense rainfall or earthquake, and it is observed that seismic high hazard zones and high rainfall areas coincide with high landslide hazard zones, it explains. The lack of safe shelter and alternate route maps for landslide hazards for important road sections and settlements has been listed among the gaps in landslide management. The strategy calls for a National Landslide Mitigation Policy (NLMP) and states developing strategy of area/problem specific but reflecting the national policy. It insists that slope instability management, reflecting the potential for sliding and landslide management, representing the ongoing event/process should be two separate components of the National Landslide Management Strategy and existing bye-laws/regulations at the local body or state level should be incorporated into the NLMP and NLMS and they should not contradict each other. Expressing concern that the present engineering practice relies on "fragmentary approaches involving quick-fix treatments of landslides, which end up in their recurrence, year after year, at the very same locations" and paucity of funds, absence of delivery capacity, and urgency to deal with immediate landslide danger are generally cited as reasons for this continuing practice. The permanent solutions to landslide problems may appear at the face value to be capital intensive and even unaffordable, but in the true analysis, the benefits of permanently fixing landslides will far overweigh, recommends the NLMS. States in the region and the Central Government aligning the landslide management activities for reducing the risk with NLMS is the urgent need of the hour.