Disaster Management and Risk Reduction: Multidisciplinary Perspectives and Approaches in the Indian Context

Rainfall-triggered landslides are a major geohazard in the Guwahati region which cannot be convincingly addressed by conventional slope stability approaches. This study attempts to address this issue with the help of advanced analysis considering the concepts of unsaturated soil mechanics involving transient/steady-state phenomena aided by the variation of pore water pressures for providing a predictive model for the potential instability under rainfall infiltration process. It is observed that the matric suction and its effect on the variation of permeability and degree of saturation, as well as the intensity and duration of rainfall, are critical factors in assessing the state of instability. Although landslides in the stated region involve relatively smaller volumes of soil (~100–400 m³), the presence of proximal urbanized areas can possibly induce significant damage to infrastructure and life loss. This study presents the applicability of physically-based models (TRIGRS, SHALSTAB and SINMAP) for assessing the regional-scale landslide susceptibility and hazard in the Guwahati region. The advantages and limitations of the different models are discussed, and the significant results are compared on the basis of the observed landslides. It is concluded from the study that physically-based models can incorporate the quantitative hydrogeological factors (e.g., soil characteristics, rainfall and areal topography) for a successful regional-scale rainfall-induced landslide hazard assessment.

The Meriema Landslide is a kind of circular failure where unconsolidated materials comprising mostly of broken rock masses of shale are found moving downslope en masse. The bedrock where this landslide occured comprised of shale belonging to the Disang Group. To be able to decipher the causes of such kinds of slumping down of pieces of broken rocks en masse geological, structural and geotechnical investigations are carried out. It could be established that the majority of the joints are radial to the length of curvature surface of the crown of the landslide. It is found plausible that the thrusting activity near the slide area caused the already developed joints particularly those perpendicular to the length of the failure surface are widen. It is also observed that the majority of the joints also dip at high angles; mostly clustering between 60–80°. From the circular surface of the crown, the maximum thickness of overburden above the failure surface at the deepest point (before slide) is also found with the help of a total station survey. The maximum vertical pressure the rocks suffered at the deepest point is then calculated which comes out to be 0.701 MPa. Comparing this value with an average shear strength of 8.32 MPa for samples of the bedrock found out from geotechnical investigations, it is learnt that the rock didn't fail on account of the load. In the rainy season during incessant rain, the rocks are saturated with water; filling all the open spaces of the joint planes with water making the friction reduced considerably, and hence the body of jointed rock mass above the failure surface could not withstand the weak shear stress. The broken pieces of rock masses could slump down over the circular surface of failure developed because of a mosaic of closely spaced and interconnected numerous joint planes dipping at various angles and directions. The Meriema Landslide is thus considered to have been controlled by lithology and structure.

The study of Saron Veng landslide is situated at the eastern limb of the Aizawl anticline. The landslide occurred on 13th June 2017 at 7:00–8:00 A.M. It swept away one residential building where seven families lived, and a link road between Saron Veng and Tuithiang Veng was blocked for more than a month. The improper drainage system, weak lithology, and high permeability also enhance the triggering factor for a landslide. The landslide covers an area of 3500 m², measuring 101.49 m in length and 44.196 m in width. The lithology of the site is composed of siltstones and sandstones, which were overlain by a thick regolith. Geological and geotechnical fieldwork was done based on various parameters like in-situ rock strength, particle size distribution for soil classification, seepage water quality, Atterberg’s limit, Direct Shear test, and analyses based on Limit Equilibrium Method (LEM). The primary soil type is coarse to very coarse sand. Water analysis shows that seepage water is fit for drinking. The average in-situ rock strength is 18N/mm²; soil can be classified as ‘slightly plastic’ from Atterberg’s values. Direct shear shows that the soil has weak cohesion. The safety factor ranges from 0.372 to 0.391, indicating that instability slope. It can be concluded as ‘debris slide,’ soft plastic type of soil, weak cohesion, and an ultimate bearing capacity of 631.88 shows that unsafe for any structure. The seepage acts as a lubricant for sliding, added by rainfalls. Benching to reduce load and decrease shear strength and proper drainage system are suggested as mitigation measures.

Landslides are the most frequent worldwide natural disaster. In landslide prone area, repetition of landslides may be observed; however, landslides may also occur in a fresh area. In the present study, a fresh landslide was observed during March 2022, at Pangthang, East Sikkim. Analysis through Geospatial Technology, ground survey and soil investigation were carried out for  the estimation of landslide susceptibility at concerned location, and it was obtained as non-susceptible; however, the landslide occurred after a prolonged untimely precipitation with high intensity, which may be the Impact of Climate Change. The analysis of the concerned slope was carried out by Bishop (1955) Method, with and without considering the effect of precipitation, and obtained the failure of slope with the effect of precipitation, because of pore water pressure. An attempt was made to provide an eco-friendly and low-cost remedial measure. To reduce the pore water pressure, sand drain has been proposed to arrest the subsurface water and to drain out through the bottom of the slope. The surface of the slope was dressed up and mixed with the vetiver grass seeds, on top of which a layer of Jute Geotextile has been placed, to arrest the surface scouring. The reinforcement of the slope has been done by using Sal-Bullah, as indigenous technology and material, which led to the sub-division of the slope height and reduction in surcharge load.

Landslides are one of the noteworthy threats to human lives and induce huge loss in terms of economical particulars. Landslide is the mass movement of debris, rocks or a slope failure, which occurs due to heavy rainfall, snow melting, earthquakes, etc. So, it is most important to scrutinize and explore the landslide susceptible zones. Accurate Landslide Susceptibility Mapping (LSM) is a pre-requisite for the development of landslide mitigation strategies. Uttarakhand, Sikkim, and Darjeeling in India are witnessing the highest landslide-prone region due to its geographical and topographical conditions. In this research paper, LSM for Sikkim and Darjeeling regions was generated with the help of Support Vector Machine (SVM) learning algorithm. For accurate LSM generation, fourteen landslide causative factors (Elevation, Slope, Aspect, Lithology, Geology, Geomorphology, NDVI, Rainfall, Soil type, Land use Land cover, Distance to roads, rivers, faults and lineaments) have been considered and respective layers were used for the LSM generation of Uttarakhand region. This generated result using Analytic hierarchy process (AHP) is fed to the machine learning model for the prediction of susceptibility mapping. The predicted LSM model is found to be 95% accurate. The proposed technique would be useful for rapid generation of LSM in highly landslide-prone regions.

Landslides are common in the North-Eastern Himalayan state of Sikkim. Landslide is a serious geo-environmental disaster causing loss of life and property. Short duration high-intensity rainfall is one of the major factors driving these slope instabilities. Out of several such landslides, the Chanmari landslide has been susceptible to major mass movements for many years and rainfall infiltration is the triggering factor for these slope movements. To mitigate landslide disasters, stabilization of the slope is of utmost importance. Installation of horizontal drains within the slope is an effective way of stabilizing the slope by reducing the pore water pressures. Horizontal drains have already been successfully installed in residual soil slopes. A numerical study was carried out to understand the effect of horizontal drains on the Chanmari slope under rainfall infiltration. Parametric studies were conducted to find out the best possible layout of the drains. The slope failed within a few minutes due to the high-intensity rainfall. The drain installed at the middle of the slope kept the minimum factor of safety of the slope higher than the slope without a drain by lowering the water level within the slope. Multiple drains placed at the middle proved to be an effective drainage system.

Rockfall constitutes one of the most disastrous hazards as it involves very rapid movements of rock blocks. Chunks of rock detach from steep slopes and undergo several kinds of motion like falling, rolling, bouncing and sliding due to gravity. Rockfall behavior is greatly influenced by the slope geometry, rock properties and contact properties. These hazards are characterized by certain rockfall parameters like bounce height, maximum runout distance, velocity attained and kinetic energy of the moving rock blocks that can be determined from their simulation. It is therefore prudent to understand the effect of characteristics like shape, size and density of the falling rock blocks on these rockfall parameters. Hence, in the present study, an attempt has been made to establish rockfall hazards through the characteristics of rock blocks. The slope geometry and other properties have been taken from the literature. It has been found that density of the rock blocks does not influence the propensity of the rockfall hazard but their shape and size acts as primary influencing factors. Additionally, sharpness of the edges of the rock blocks was also found to have a marked influence on the rockfall parameters. The impact energy exerted by the falling rocks on the barrier was also studied considering the effect of their shape and size characteristics.

Sivok-Rangpo Rail Line Project (SRRP) is traversing along the Teesta River Valley through the seismically active Darjeeling and Kalimpong Hills in between MBT and MCT of Darjeeling-Sikkim Himalaya (DSH). Therefore, many environmentalists and geologists claimed that this project dominated by tunnels may invite natural disasters and the tunnels will not be safe under seismic events. From the studies like empirical correlations between measured peak ground accelerations (g) and observed damage in tunnels, the following tendencies have been revealed: (a) up to a peak acceleration of 0.2 g, slight damage, (b) from 0.2 g to 0.6 g, serious damage in unlined tunnels and in tunnels devoid modern lining, (c) from 0.6 g to 0.9 g, serious damage on tunnels having plain concrete lining (unreinforced). Though most severe earthquakes in Sikkim and adjoining areas had peak ground acceleration ranges from 0.15 g to 0.45 g only, which indicate that the modern lined tunnels constructed by NATM are very much safe under massive earthquakes, and NATM designs have all considerable factors for earthquake-induced ground movement in them. The transportation tunnels ensure less damage to the environments and biodiversity and are also used to avoid instable slopes which fail during earthquake-induced ground vibration. Therefore, tunnels are considered as safe and useful in sustainable infrastructural developments in this seismically active Himalayan region.

Normal life is regularly disrupted in Kohima, the state capital of Nagaland, due to frequent incidences of land instabilities. Six unstable and two stable areas sharing similar geology in different parts of the town were selected for electrical resistivity study. Vertical Electrical Sounding (VES) was carried out to determine the subsurface conditions by analyzing variations in the resistivity values following the Schlumberger configuration. The objective of the present study is to evaluate the influence of subsurface conditions on surface instabilities. The VES data show three to five subsurface geo-electric layers, comprising of the topsoil followed by various rock layers that are found to be weathered and fractured. K type is the dominant curve which indicates higher saturation at the lower strata. Existing borehole data were used to validate the results of the VES. Thickness of soil overburden, types and condition of the subsurface rocks, the depth of water table have some influence on the type and incidences of slope instabilities.

On February 7 2021, a debris flow in Dhauliganga and Rishiganga Valley in Chamoli (30.2937° N, 79.5603° E) wreaked havoc on the downslope. This debris flow caused the death of at least 80 people and the missing of 124 people. It nearly swept away the Rishiganga hydropower plant and severely damaged the Tapovan Vishnu gad Hydropower. The initial claim was that the cause of this disaster was ‘Glacial lakes outburst flood’ (GLOF). However, geologists and glaciologists scrapped this claim after studying the images before and after the event. There was no detailed experimental research or modelling to understand the origin of the flash flood in this paper. In this review, an attempt has been made to understand the cause of the flood event and challenges to the infrastructural project. Such an attempt is significant for the North-eastern region of India. The mountains in this region have a similar composition as those in the Chamoli district. Studies have shown that rapid infrastructure in this region of the country harms its mountains. Hence, the lesson learnt from the Chamoli disaster will help to shape the disaster risk reduction programs and future mitigative measures in the northeast region.

The Critical Zone thickness (CZT) is defined as the depth from the top of the canopy to the topmost zones of the water table. Critical Zone monitoring is important, as it is the most dynamic part of our atmosphere and it is very vulnerable and suffers the most due to human influence. In this study, we have derived the CZT of Assam. CZT was derived by adding the vegetation height and water table depth. The analysis shows that the CZT for Assam varies from 5.228 m to 78.638 m. The vegetation height varies from 1.632 m to 74.529 m. We have classified the region as having low, medium, and high CZT. Based on the comparison with the Landslide Hazard Zonation map derived from the previous literature, it was found that the CZT correlates with the Landslide Hazard Zonation map. Hence, this study could prove substantial for Disaster Management authorities to take necessary steps for mitigation purposes.

Civil engineers can play a crucial role by contributing to the field of disaster management in two important ways. First is by setting of design and safety standards, and second by actually designing and constructing infrastructure such as to prevent damage and losses caused by hazards. Past earthquake case histories show that structures supported by different types of foundations are affected in a different manner depending upon the type of earthquake and the type of foundation. Thus proper seismic investigation of already existing structures along with conducting seismic studies while designing new structures has become very important. In this research work, static pushover analysis is conducted on different piles embedded in stratified soil having different combinations of surrounding soil layers. An attempt is made to incorporate static pushover analysis, which is simple and less time consuming into the seismic requalification procedure provided by Krishna et al. (2014), to simplify the entire process of estimation of the damage level of the foundation and determine if seismic requalification is required. The seismic analyses are conducted in OpenSees PL which has the ability to reproduce SSI effects due to earthquake loading computationally and thus can be used to conduct FE computations to obtain realistic results of seismic analyses.

Artificial neural networks and the mode shape curvature technique are used to assess the severity and locations of damages using experimentally recorded displacement mode shapes as input data. The Bruel and Kjaer instrument with an impact hammer is used to obtain frequency responses such as displacement mode forms with varied damage levels. Three-mode forms are first considered. It is shown that without further investigation, the recorded frequency response (displacement mode shapes) is insufficient to localize the damage. Artificial neural network training processes are utilized to reduce measurement error from the measured frequency response data set. Using central difference approximation, the training data sets are then used to generate the mode forms curvatures.

Solid waste is one of the many factors that negatively affect the environment. Plastic is an important type of solid waste with a strong environmental impact and is difficult to recycle and reuse. In order to decrease the plastic waste, many researchers have conducted various researches on concrete and have come up with innovative ideas of using plastic waste in concrete which not only helps in mitigating plastic waste problems but also helps in enhancing the compressive characteristics of a concrete. In this study, conventional concrete is studied under compression loading and compared with modified concrete samples having horizontally oriented plastic strips (MC-H). Three different arrangements of PET strips are considered. In the first arrangement, two layers of PET strips spaced at an equal distance of 50 mm between the concrete grades of M30. In the second arrangement, five layers of PET strips placed at an equal distance of 25 mm are placed. And lastly in the third arrangement, eleven layers of PET strips, each being separated by a distance of 12.5 mm. From load and deflection control tests, it is concluded that plastic (PET) strips positively contribute to concrete behavior in terms of increased stiffness and higher strength.

A massive catastrophic landslide wiped out the Malin village on July 30, 2014. The occurrence of such landslides cannot be prevented, but its effects can be minimized by taking timely preventive measures. This event has revealed the mismanagement of vulnerable hills of India. The 2014 Malin landslide has taught the lesson that the disaster management fraternity is yet to evolve in terms of pre-disaster mitigation strategies. There is an ardent necessity to start working on strategies to prevent a repetition of such costly disasters in nearby future. In this critical review, various aspects of the catastrophe are elucidated and the mitigating measures are described. A perspective towards the future direction of management is also provided. Such an attempt is important especially for the north-eastern region of India as the regional hillslopes are tremendously wetted by prolonged, incessant and recurrent rainfall. Hence, the lessons learned from the 2014 Malin landslide should help to develop an efficient preventive system against such similar occurrences in the future.

North-East (NE) India has experienced several devastating earthquakes in the past decades. The seismic susceptibility of reinforced concrete frame buildings has been exposed by these earthquakes. In this region, most of the existing buildings are non-ductile as they are built before the introduction of modern seismic design codes. Seismic safety and resilience of these non-ductile structures can be increased by the use of a reliable retrofitting scheme. Therefore, buckling-restrained braces (BRBs) are designed to withstand earthquake-induced cyclic lateral loadings as a passive control system. In this study, the influence of BRBs in reducing the seismic risk of non-seismically designed frame is discussed. A finite element model of a 3-story 3-bay low ductility moment-resisting RC frame is developed. Nonlinear time-history analyses are carried out using a suite of ground motions to incorporate record-to-record variability. For both as-built and BRB retrofitted frame seismic fragility curves are obtained. For seismic risk assessment, the site-specific seismic hazard curve of Guwahati city giving relationship between annual probability of exceedance and peak spectral acceleration at 1.0 s is obtained. The estimation of seismic risk reduction as a result of the application of the BRBs retrofit within the bare frame is done by convolution of the seismic fragility curves with the regional seismic hazards for the Guwahati region. The findings of this study present the significance of BRBs on the seismic performance of the building, as well as the efficacy of a BRB retrofit for the NE region.

Disaster Management is thought to start only after a disaster has struck. But that is only a part of the overall management strategy. We are increasingly waking up to the fact that Disaster Management should start much ahead and avoiding disasters is the best way to manage them. This calls for building a resilient society. For the last few decades environmental irregularities have become more frequent across the globe, which scientists claim to be the signs of an irreversible climate change. Scientists are clamouring for the need to build mitigating and adaptive measures in local, national and global policies to face this challenge. In this paper, we start with a broad outline of disasters, resilience, damage costs and avoidance costs. We also explain why we find resilience planning to be generally underfunded in developing countries. We then discuss the consequences of such under-preparedness using three case studies of cyclone management in India to understand the complexities of resilience planning and extreme event management policies. We also examine how the pandemic had affected resilience activities during one of the extreme events chosen for study. In the final section we outline the lessons learned from this experience and the policy response that may be put in place to deal with such situation—which looks to become increasingly regular in near future. The paper helps in bringing to limelight the problems faced during multiple extreme events.

In the context of flood management, Blue-Green Infrastructure (BGI) can be defined as the network of natural & designed landscape components that include blue and green spaces, and green spaces are designed to turn blue during extreme rainfall & flood events. BGI provides multifunctional benefits like less urban water discharge, better climate change adaptation, less water pollution, increased biodiversity, and water storage. Even at an individual level, green space promotes good health, well-being, and better physical & mental development. Developed countries like Europe & North America have promoted the use of Green Infrastructure (GI), emphasizing more on environmental sustainability. Copenhagen mandated the use of green roofs as a BGI measure in 2010 which absorbs 50–80% of their annual rainfall, delays discharge & reduces the urban heat island effect. In Portland City, the Downspout Disconnection project (1993–2011) alone can attribute to 1.2 billion gallons of stormwater discharge reduction. In Toronto City, building with greater than or equal to 2000 m² area must apply green roofs in 20–60% of their area. Japan mandated green roofs in all the newer constructions. The developed countries are taking benefits both in terms of cost & ecology by shifting from grey to green. But in India, the main focus is on housing & transportation development. In the Indian context, it is challenging to implement BGI because of the rapid urbanization and the hierarchical model. Thinking & implementing BGI had already begun in metropolitan cities like Ahmedabad and Mumbai. But, until now, no proper general framework has been available. Our study area is focused mainly on Guwahati City. The city is a major commercial and educational hub of Assam and the gateway for the north-eastern region of India. The city witnesses flooding as a recurrent event. The focus of our work is to identify the possible improvements for the Guwahati Smart City by analyzing the existing infrastructural gaps in the city, the objectives of the Smart City Programme & how Guwahati plans to develop its own Smart City. The study aims to see what could have been the critical GI implementations in the Smart City Project to obtain its objectives & whether the BGI implementation was done fractionally or not.

A considerable portion of the farmers and people in rural areas, especially in Assam, involved in agricultural practices are solely dependent upon climatic factors for producing crops. Crops, too, are sensitive to climatic conditions and other environmental factors and failing to provide the right environment at the right time eventually leads to loss of productivity. Hence, it is prudent that a system is devised in the form of an early warning system such that farmers can be made aware of any irregularities in rainfall in advance, thereby avoiding massive losses to crops. A long-term precipitation analysis over 120 years is performed for the Kamrup Rural region using gridded data provided by the Indian Meteorological Department. The MK-test, Sen's Slope and EMD method which is proposed as an effective alternative for trend identification of series, has been used for trend analysis. Additionally, an attempt is made to develop a rainfall forecasting model using recurrent neural networks such as Long Short-Term Memory.

In a view of increasing fire incidences and risk of climate change on the ecosystem, current study has been carried out in Mizoram state of north east India which is one of the fire-prone states in the country. The study is carried out to analyse the effect of climatic variables (precipitation, temperature and humidity) on forest fire occurrence using trend analysis (MK test) and spatial relation between the two. Active fire points (MODIS) from 2003 to 2020 and gridded climate data (ERA 5 & FLDAS) were used for spatial analysis. Significant (at 95% confidence level) trend analysis showed an increase in temperature (1.97–3.03) and humidity (1.98–3.18) in monsoon and post-monsoon seasons. Precipitation was observed to decrease in September for Lawngtlai (−2.05) and Mamit (−1.97). Overall forest fire occurrence in the state was found to be decreasing while spatial analysis over the state showed an increasing trend in parts of Mamit, Lunglei and Lawngtlai districts. The same region was found to have negative relation for temperature in winter season while rest of the state had positive relation with fire occurrence. Precipitation and humidity both were having negative relation to forest fire occurrence with exception of areas mentioned earlier, with positive relation in winter, premonsoon (precipitation) and monsoon seasons (humidity). Despite the major role of anthropogenic activities in forest fire in the state, the variability in results suggests that forest fire occurrence may be due to the response of climatic conditions, but it is restricted to certain areas.

Groundwater is essential for energy and food security, human health, and ecosystems. The precise prediction of groundwater depth is essential for the adequate utilization and management of groundwater resources. The present study aims toward the temporal trend analysis of groundwater depth for pre and post-monsoons by performing Mann–Kendall’s (MK) test and linear regression method for Greater Guwahati Area (GGA). The study also aims to prepare spatial groundwater table fluctuation using a geographic information system (GIS) by using spatial interpolation techniques for different years. The current study shows that the average annual groundwater level (GWL) during all the monsoon seasons in the southeastern parts of the study area has fallen below 8 m below ground level (bgl), highlighting low rainfall infiltration and excessive exploitation of groundwater. The average water level ranges from 1.24 m to 20.07 m during the pre-monsoon and from 0.33 m to 10.96 m during the post-monsoon season. The study revealed that the water level during pre-and post-monsoon seasons lies between 4 and 8 m bgl in 23% of the wells. Spatial variation maps describe that the GWL in the southeastern parts of the basin falls by more than 8 m in all monsoon seasons. Pettitt’s change point tests also depict that most change points occurred during the 2012–2014 period in the GGA. Therefore, this study suggests implementing a large-scale rainwater harvesting system in the GGA to augment groundwater resources.