---

High Resolution Remote Sensing data characterization of geoaspects in a Himalayan Terrain and their implication on landslide occurrence in this region- A case study from Silcher-Aizwal Region, Mizoram, India

Dr. A.C Pandey, Mr. Gulab Singh,
'Dept of Remote Sensing , Birla Institute of Technology , Mesra, India
Ms. Hina Pandey, Ms. Poonam Seth
Scientist, IIRS , Dehra Dun, India
Email:- arvindchandrap@yahoo.com, hina@iirs.gov.in, poonam@iirs.gov.in

ABSTRACT:
Geology and geomorphology define the geo-aspects of a region. The development of drainage pattern to a large extent is controlled by the geological formation whereas the relief is the sum total of tectonic and geomorphic processes operated in the region in the geological past. Remote sensing is an important and effective aiding tool in geological- geomorphological mapping. Remotely sensed images provide a wealth of information of large areas of the earth's surface and permit evaluation of regional geological structures, broad lithological discrimination and spatial distribution of landforms. The study area lies in the Aizwal districts of Mizoram state. It is located between 92° 37’ 30’’E to 92° 45’ 00’’ E longitudes and 23° 40’ 00’’N to 24° 00’ 00’’ N latitudes and measures for about 472 sq. km in the Survey of India topographic sheets 84 A/9 and 84 A/10. Aizwal is the major township of the area. In this region severe erosion and concomitant land sliding in rainy season constitutes the main geo hazard. Since the intricate relationship of lithological, structural and geomorphic parameters are related to slope instability phenomena, the assessment of landslide proneness and soil erosion patterns requires appraisal of these factors. In the present work the geological and geomorphological investigations were carried out on a regional scale based on interpretation of IRS LISS-III and PAN merged satellite images on scale 1:25,000 scale. On a regional scale the area under investigation is surrounded north-south trending hill ranges comprising of rocks of Tipam and Surma group, consisting primarily of alternate sandstone and shale. The Silchaer-Aizwal region is characterized by a large number of lineaments, which represent regional joint patterns, major fractures, anticlinal or synclinal fold axes as well as faults. The landforms developed in the terrain of Silchar-Aizwal region are dominantly young and immature. It shows prominent relief features with steep slopes and is still undergoing active denudation in response to various exogenic and endogenic processes. Most of the landforms are erosional in nature with fluvial dynamics as the most dominating process involved in landform development. Based on image-interpretation and field investigations, a number of geomorphic landforms viz., hills and river valleys, river terraces, sand bars, flood plains, gully erosion, landslides etc. were identified. The landslide density analysis reveals that the rock of Upper Bhuban formation (sandstone with shale) exhibit high landslide density as (0.003) as compared to other lithological units present in the area. This suggests that the slope instability in the study area is largely influenced by the sandstone with shale association. Spatial distribution of lineament density shows that area of high lineament density corresponds to areas of high dissection index. Geomorphology governs the surface processes and play a significant role in inducing landslides and erosion. Landslide density analysis indicated that maximum landslide density as well as landslide frequency occurs in the areas, which are highly dissected. This is probably due to high rate of weathering and erosion in the dissected regions coupled with weak rock types.