Dericks P. Shukla

GIS-based morpho-tectonic studies of Alaknanda river basin: a precursor for hazard zonation

Abstract Alaknanda river basin is considered to be tectonically active where damaging earthquakes and landslides have occurred. The whole basin was divided into 8 sub-basins to carry out morphometric analyses, hypsometric integral (HI) analysis and valley floor width to valley height ratio (Vf) factor. The sub-basins 2 and 3 show that they are highly active, because of the higher values of bifurcation ratio, stream frequency asymmetric factor, and lower values of form factor, elongation ratio and circulatory ratio. In these areas, HI values are very low indicating that the landscape is highly eroded, deeply dissected and tectonically active. The result obtained from Vf was similar which classified both these basins as highly active. Morphometric analysis, HI and Vf analyses along with structural map of study area are used to prepare morpho-tectonic map classifying the whole area into very high, high, moderate and low zones of tectonic activity. This map clearly indicates that the areas near MCT II (Munsiari Thrust), MCT III (Ramgarh Thrust) and North Almora Thrust are tectonically very active which fall in sub-basins 2, 3, 4 and parts of 5. Various locations such as Chamoli, Birahi, Pipalkoti, Rudraprayag, etc. are situated in these zones where many earthquakes and landslides occur every year. Moreover, the data plotted for earthquakes and landslides occurrences are consistent with morpho-tectonic map and can be used as a precursor for demarcation of natural hazard vulnerable zones.

Geo-spatial Technology for Landslide Hazard Zonation and Prediction

Similar to other geo hazards, landslides cannot be avoided in mountainous terrain. It is the most common natural hazard in the mountain regions and can result in enormous damage to both property and life every year. Better understanding of the hazard will help people to live in harmony with the pristine nature. Since India has 15% of its land area prone to landslides, preparation of landslide susceptibility zo‐ nation (LSZ) maps for these areas is of utmost importance. These susceptibility zo‐ nation maps will give the areas that are prone to landslides and the safe areas, which in-turn help the administrators for safer planning and future development activities. There are various methods for the preparation of LSZ maps such as based on Fuzzy logic, Artificial Neural Network, Discriminant Analysis, Direct Mapping, Regression Analysis, Neuro-Fuzzy approach and other techniques. These different approaches apply different rating system and the weights, which are area and fac‐ tors dependent. Therefore, these weights and ratings play a vital role in the prepa‐ ration of susceptibility maps using any of the approach. However, one technique that gives very high accuracy in certain might not be applicable to other parts of the world due to change in various factors, weights and ratings. Hence, only one meth‐ od cannot be suggested to be applied in any other terrain. Therefore, an under‐ standing of these approaches, factors and weights needs to be enhanced so that their execution in Geographic Information System (GIS) environment could give better results and yield actual ground like scenarios for landslide susceptibility mapping. Hence, the available and applicable approaches are discussed in this chapter along with detailed account of the literature survey in the areas of LSZ mapping. Also a case study of Garhwal area where Support Vector Machine (SVM) technique is used for preparing LSZ is also given. These LSZ maps will also be an important input for preparing the risk assessment of LSZ.

Neotectonic activity and the origin of Tso Morari Lake using remote sensing and digital elevation model (DEM) derivative techniques

Neotectonics play an important role in the formation of lakes, especially near active suture zones. The best suited areas where such changes are observed are the tectonically active mountainous regions of Himalaya. However, in an inaccessible terrain like Higher-Himalaya, active tectonic studies related to development of newer and reactivated faults are less conceived. In this article, an attempt has been made to identify active faults and Neotectonic activity in the Tso Morari area in Ladakh, North-West Himalaya, with the help of remote sensing and digital elevation model (DEM) techniques. The results suggest that Tso Morari Lake is developed due to Neotectonic uplift in the region which created a fault scarp in E–W direction. The horizon blocking technique with the aid of elevation, slope and aspect map is used to demarcate the E–W trending younger fault. Moreover, the earthquakes foci also lie along this E–W direction which has restricted the seismic activity to its southern part.