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Thiruvananthapuram, India

Vijith H.,Kerala University | Vijith H.,Curtin University Australia | Prasannakumar V.,Kerala University | Krishnan M.V.N.,Institute of Land and Disaster Management | Pratheesh P.,Kerala University
Georisk | Year: 2015

ABSTRACT: Neotectonic activity in Mahe (Mayyazhi) river basin and its implication in landform development and stream characteristics were investigated with the help of the digital elevation model-derived geomorphic indices. The analysis is based on the commonly used geomorphic indices such as hypsometric curve and integral, drainage basin asymmetry, transverse topographic symmetric factor (T), stream length (SL) gradient index and longitudinal profiles of the stream. Hypsometric integrals indicate that the basin has reached the base level and lesser amount of material remains for erosion and transportation. The basin is asymmetric and has a south-south-east directional tilt, but with a probable spin caused due to the presence of major strike slip fracture, the mouth portion of the Mahe river has been tilted towards north-north-west. The SL index with sudden and non-uniform variations supports the finding and indicates the relative tectonic activity and its influence over the river networks in the area. Longitudinal profile of the stream also reveals gradational changes in the profile with the presence of knick points. Cross comparison of the analysed geomorphic indices points towards neotectonic activity in the basin, which modified the river basin to the present morphology and is reflected in the characteristics of the river and the basin as a whole. © 2015 Taylor & Francis.

Vijith H.,Institute of Land and Disaster Management | Vijith H.,Curtin University Australia | Prasannakumar V.,Kerala University | Mohan M.A.S.,Kerala University | Pratheesh P.,Kerala University
Geocarto International | Year: 2015

The anomalous channel pattern in the midland stretch of the river Karamana, having highly sinuous and incised course with varying floodplain, is analysed to determine the different stages of evolution of the river channel in response to the structural disturbances in the area. Geometric analysis of foliation, geospatial analyses of sinuosity index, hypsometry, channel and streamline changes, river channel cross-profile, longitudinal profile and derivation of fold structure from satellite images were attempted in evaluating the characteristic features of the selected river segment. Datasets used in the analysis were collected through the detailed fieldwork, structural mapping and interpretation of satellite images and satellite-derived digital elevation data. Systematic analysis of the channel pattern of the selected reaches of the river, in 1915, 1968 and 2008 classifies the river as tortuously meandering. Implications of tectonic disturbance can be inferred from the presence of channel incision, unpaired terraces, younger terrain with intense erosion, knick points, convex river long profile, and high hypsometric integral, oscillating and unpaired character of the river channel. Structural analysis along with GIS and remote sensing studies proved the presence of a major fold with a NW–SE-trending axial surface. An evolutionary model is proposed to elucidate the channel planform changes in response to the deformation and tectonic uplift of the region. © 2015 Taylor & Francis.

Vijith H.,Kerala University | Vijith H.,Curtin University Australia | Prasannakumar V.,Kerala University | Pratheesh P.,Kerala University | And 2 more authors.
Arabian Journal of Geosciences | Year: 2016

Geomorphic expressions embedded within the bedrock channels, originating from the southernmost part of the Western Ghats, India, are quantitatively characterized through well-defined geomorphic indices using digital elevation models (DEM) and geographical information system (GIS) tools. Drainage basin asymmetry (Af), transverse topographic symmetry factor (T), longitudinal profile, stream length gradient index (SL), hypsometric integral and curve (Ihyp), spatial parameters like drainage density (Dd) and dissection index (DI) are used for extraction of information related to the characteristic pattern and behaviour associated with the Karamana river and its two major tributaries. The independent and cumulative analysis of each geomorphic indices indicates adjustment of Karamana river in response to the tectonic activities. Karamana basin, while showing symmetric character as a single unit, exhibits segments of asymmetric nature associated with the terrain tilting and is evidenced from the variable directional oscillation from E, SSE, S, NW and W. Varying characteristics of the longitudinal profiles and abrupt change in the SL index suggest knick points and uplift of the terrain due to tectonic processes. The influence of tectonic process over the stream characteristics is confirmed by identifying higher levels of SL anomalies in unique lithology. The inferences correlate with the low drainage density and high dissection index zones in the region with varying influence of tectonic processes. Though, the Karamana river basin as a single unit shows old age characteristics in the hypsometric analysis and symmetric nature, the longitudinal profile-assisted SL and SL anomaly indices are found to be capable of revealing evidences of differential effects of tectonic activities over the stream characteristics. The deductions are in agreement with field observations on landforms and channel attributes. © 2016, Saudi Society for Geosciences.

Illiyas F.T.,Institute of Land and Disaster Management | Mani S.K.,Tata Institute of Social Sciences | Pradeepkumar A.P.,Kerala University | Mohan K.,Institute of Land and Disaster Management
International Journal of Disaster Risk Reduction | Year: 2013

Human stampedes have been identified as a major hazard that could occur during mass gathering events in India, as well as anywhere in the world where people crowd together. This study compiles and analyses stampede data from religious, entertainment and political gatherings over the last five decades in India to derive an effective risk reduction framework for mass gatherings. Religious gatherings and pilgrimages have been venues for 79% of the stampedes in India. Noticeable occurrences and casualties have been reported from 15 Indian states and there have been instances of recurrent stampedes at certain locations. Risk management strategies to tackle stampedes during religious festivals are quite inadequate and have failed consistently in India because of the large crowds and the constantly widening spread of the venue. The triggers of human stampedes have been identified from case studies and it is concluded that a simple accident, an intentional act or even a rumor can trigger a crowd disturbance. Hence the organizers have to take into consideration the causes of crowd disturbance for ensuring safety in mass gatherings. The vulnerability of religious gatherings is also increased due to venue inadequacies like remote or hazard-prone setting, poor facilities, or lack of basic infrastructure and medical care centers. The risk factors identified from the study of past incidents have lead to the development of a basic framework aligned on four interlinked compartments for inter-agency cooperation and multi-disciplinary contemplation ranging from hazard identification to the execution of mitigation measures for human stampede risk reduction. © 2013 Elsevier Ltd.

Vijith H.,Institute of Land and Disaster Management | Krishnakumar K.N.,Kerala University | Pradeep G.S.,Institute of Land and Disaster Management | Ninu Krishnan M.V.,Institute of Land and Disaster Management | Madhu G.,Cochin University of Science and Technology
Georisk | Year: 2014

The study aims to prepare a landslide susceptibility zonation (LSZ) map and quantitative validation of the result at a scale of 1:50,000 for the upland catchment of river Meenachil, Kottayam district, Kerala, India by recognizing and mapping the palaeoslide locations and the associated terrain attributes. A bivariate statistical method, known as the weights of evidence modeling, which offers a flexible way of testing the importance of input factors used for landslide susceptibility assessment, were used for the analysis. Fourteen terrain parameters namely, geomorphology, drainage density, soil type, soil thickness, land use, Normalized Difference Vegetation Index (NDVI), slope, aspect, relative relief, slope length, profile curvature, plan curvature, flowpath length and topographic wetness index were generated and its weights were determined. The conditional independence of the evidential themes was assessed by 'Omnibus test' and those themes which found to be conditionally independent were integrated to produce the final LSZ map. The results shows that areas having slope less than 16° is classified as stable areas since the active geomorphic processes are absent there, areas covered by side-slope plateau and denudational hills constitutes the very high and high susceptible region and is contributed by the slope between 16° and 45°, facing southwest, west and northwest directions, with extended influence from relative relief, slope length, flowpath length and compound topographic index. The reliability and accuracy of the LSZ map was assessed by the receiver operating characteristic curve analysis and the model shows a prediction accuracy of 89.2% (area under the curve = 0.892). In order to enhance the utility of the results of the present study, a panchayath-wise (the lowest administrative body) susceptibility map was produced and it shows that, among these panchayaths, highly susceptible areas are found in Munnilavu, Talanad, Tikoy and Poonjar Thekkekara. Suggestions are also drawn to optimize the hazard assessment for the region having high landslide susceptibility. © 2014 © 2014 Taylor & Francis.

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