ENC Perera

The recent construction boom taking place in the country together with the providence of facilities to the unprecedentedly rising arrivals of tourist due to the scenic beauty and mild environment, there is a dramatic increase of the development activities in hilly area of the island. Also it is noted that some of the communities living in congested cities and suburbs migrate to hilly areas in order to find a less congested residential areas. Due to these reasons, some of the slopes which were earlier at equilibrium, are becoming unstable due to modification of slopes and haphazard development occurring in the already unsuitable areas. However, for the sustainable development, all development activities must be in compliance with requirements of a hazard free environment. Hence, pre-identification of areas susceptible to landslides have become a timely requirement to eliminate possible hazardous situations.

Landslides were one of the major damage disasters which occur in the world. It frequently leads to serious problems in Hilly areas during the rainy season. In this present study, the multicriteria analysis techniques were used to determine the landslide Hazard zonation and also the various factors of different thematic layers such as geology, type of soil, land surface temperature, land cover, Level slope aspects of underground water and inclination of slope were integrated in GIS to outline landslide hazards. The critical hierarchy was used to find out the various weightage's values of different factors of thematic layers. The development of Landslide Hazard zonation map for Kotargiri was created on different techniques such as Ranking and weightages and overlay techniques. The developed landslide Hazard map of Kotagiriarea in India was divided in to exposed zones such as high, moderate, poor, very high. The resulted landslides hazarded zonation was further confirmed with field study and geospatial technology analysis. The results confirm that the elevation range in Kotagiri are highly prone to landslides. The final landslides hazards Zonation map can be used for the preventing landslide in that area.

Landslide is the main cause of massive damage in tectonically active hilly terrain of the Himalayan region including the state of Mizoram. It can be disastrous causing destruction to life and property, and may also lead to large scale landscape transformations. The main causes of landslide can be attributed to unplanned human activities in the areas that are liable to its occurrence. Such areas are commonly found within the township and cities where various infrastructural amenities and constructions are carried out without proper awareness of site safety and feasibility. Mamit is a small town, and is the headquarters of the recently formed Mamit district. In the present context, the landslide hazards areas are confined in few places due to the stable environment and limited anthropogenic activities within the town. However, the geo-environmental condition can become worst in this growing town unless proper planning for developmental activities is done. Therefore, the present study was taken up to investigate the Landslide Hazard Zonation (LHZ) of Mamit town using high resolution satellite data. Using Remote Sensing and Geographic Information System (GIS) techniques, thematic layers like slope morphometry, geological structures like faults and lineaments, lithology, relative relief and land use / land cover were generated. The weightage rating system based on relative importance of various causative factors was used for different classes of thematic layers. The classes were assigned the corresponding rating value as attribute information in the GIS environment. Each class within a thematic layer was assigned an ordinal rating from 0 to 10. Summation of these attribute value were then multiplied by the corresponding weights to yield the different zones of landslide hazard. A landslide hazard zonation map was prepared showing five different zones ranging from very low hazard zone to very high hazard zone which is essential for carrying out quicker and safer mitigation programmes, as well as for future developmental planning.

Saiha district, Mizoram is prone to natural hazards like landslide, earthquake, etc. Landslide is one of the natural disasters, which involves sliding of mass of earth or rock down the slope along a definite zone or surface. Landslide Hazard Zonation may be defined as a technique of classifying an area into zones of relative degrees of potential hazards by ranking various causative factors operative in a given area based on their influence in initiation of landslides. Landslide Hazard Zonation map is prepared based on the integration of data acquired from various geo-environmental thematic databases. Combining various controlling parameters by giving different weightage value for all the themes, the final map is derived in a GIS environment on 1:50,000 scale. The area and the map is then classified into Very high, High, Moderate, Low and Very low hazard zones. Very High Hazard Zone constitutes an area of 138.44sq. km and forms 9.89% of the total district area and High Hazard Zone occupies 340.85sq. km which is 24.35% of the total district area while Moderate Hazard Zone constitute an area of about about 598.07sq. km and occupies 42.72% of the total district area; Low Hazard Zone extends over an area of about 279.47sq. km and forms 19.96% of the total district and Very Low Hazard Zone covers an area of about 31.1sq km and forms 2.22% of the total district area

Landslides occur in hilly regions that are prone to activities of urban development, agricultural activities, construction of dams and road and railway network. The slope instability in hilly slope areas is due to construction activities, clearing the natural vegetation, unplanned resort development tourist activities, etc. The landslide susceptibility mapping is an effective tool for the development of hilly areas to analyse the slope stability along the road network. This paper attempts a GIS based multi-criterion methodology to identify landslide susceptibility zonation in CNG (Calicut -Nilampur -Gudalur) -37 ghat section in Nadugani, Gudalur taluk, The Nilgiris district. The environmental geological factors used for the landslide susceptibility analysis include, geology, weathering thickness, geomorphology, lineament, lineament density, lineament intensity, lineament buffer and slope. By applying and integrating the multi-criterion weights using ArcGIS software, a landslide susceptibility zonation is obtained and the study area is divided into five classes which include very low, low, moderate, high and very high regions. The susceptibility zonation map shows that 1.60% in Very low, 18.49% in Low, 40.39% in Moderate, 33.78% in high and 5.74% very high hazard zone. The landslide susceptibility zonation map is validated with landslide points which were collected from the field using high performance GPS. According to landslide inventory details 1.25% is located in very high, 24.27% in high, 55.66% in moderate, 18.83% in low and 0% in very low hazard zones.

Landslides are one of the critical natural phenomena that frequently lead to serious problems in hilly area, resulting to loss of human life and property, as well as causing severe damage to natural resources. The local geology with high degree of slope coupled with high intensity of rainfall along with unplanned human activities of the study area causes many landslides in this region. The present study area is more attracted by tourist throughout the year, so this area must be considered for preventive measures. Geospatial based Multicriteria decision analysis (MCDA) technique is increasingly used for landslide vulnerability and hazard zonation mapping. It enables the integration of different data layers with different levels of uncertainty. In this present study, it is used analytic hierarchy process (AHP) method to prepare landslide hazard zones of the Coonoor and Ooty, part of Kallar watershed, The Nilgiris, Tamil Nadu. The study was carried out using remote sensing data, field surveys and geographic information system (GIS) tools. The ten factors that influence landslide occurrence, such as elevation, slope aspect, slope angle, drainage density, lineament density, soil, precipitation, land use/land cover (LULC), distance from road and NDVI were considered. These factors layers were extracted from the various related spatial data's. These factors were evaluated, and then, the individual factor weight and class weight were assigned to each of the related factors. The Landslide Hazard Zone Index (LHZI) was calculated using Multicriteria decision analysis (MCDA) the technique based on the assigned weight and the rating is given by the Analytical Hierarchy Process (AHP) method. The final cumulative map of the study area was categorized into four hazard zones and classified as zone I to IV. There are 3.56 % of the area comes under the hazard zone IV fallowed by 48.19 % of the area comes under zone III, 43.63 % of the area in zone II and 4.61% of the area comes hazard zone I. Further resulted hazard zone map and landuse/landcover map are overlaid to check the hazard status, and existing inventory of known landslides within the present study area was compared with the resulting vulnerable and hazard zone maps. The landslide hazard zonation map is useful for landslide hazard prevention, mitigation, and improvement to society, and proper planning for land use and construction in the future..

International Journal of Geosciences, 2013

The paper presents a methodology for landslide hazard zonation mapping using GIS and remote sensing data. The study has been carried out along NH-1A-Udhampur to Banihal in Kashmir Himalaya as this terrain is prone to the landslide hazards. The present study has been made to derive and identify the important terrain factors contributing to landslide occurrences in the region and corresponding thematic data layers are generated in GIS domain. These terrain data are collected from the topographic maps, satellite imageries, field visits and available published maps. A GIS database is prepared by digitizing these maps along with tabular data and their corresponding weightage is assigned using Analytic Hierarchy Process (AHP) based criteria ranking method for determining the standardized scores of criteria expressing their factor of importance for a given decision problem in terms of thematic parameters, categories and their normalized weights. Statistically integrating weightages from these thematic maps, a specific landslide hazard map was developed on a GIS platform. The resulting landslide hazard zonation map delineates the area into different zones of six classes of landslide hazard zones i.e., severe, very high, high, moderate, low and very low.

Lawngtlai district, Mizoram is prone to natural hazards like landslide, earthquake, etc. Landslide is one of the natural disasters, which involves sliding of mass of earth or rock down the slope along a definite zone or surface. Landslide Hazard Zonation may be defined as a technique of classifying an area into zones of relative degrees of potential hazards by ranking various causative factors operative in a given area based on their influence in initiation of landslides. Landslide Hazard Zonation map is prepared based on the integration of data acquired from various geoenvironmental thematic databases. Combining various controlling parameters by giving different weightage value for all the themes, the final map is derived in a GIS environment on 1:50,000 scale. The area and the map is then classified into Very high, High, Moderate, Low and Very low hazard zones. Very High Hazard Zone constitutes an area of 221.82sq. km and forms 8.67% of the total district area ; High Hazard Zone occupies a fairly large area i.e, about 446.76sq. km which is 17.47% of the total district area; Moderate Hazard Zone constitute an area of about 1084.30sq. km and occupies 42.41% of the total district area; Low Hazard Zone extends over an area of about 597.0sq. km and forms 23.35% of the total district area and Very Low Hazard Zone covers an area of about 188.67sq km and forms 7.38% of the total district area.

IJIRST, 2014

A methodology for landslide hazard zonation mapping using an integrated remote sensing and GIS approach is presented. Landslides often affect Kodaikanal, a well-known tourist hill resort in south India, The hills in Kodaikanal have a fairly thick weathered overburden that tend to slide during heavy rainfall. Therefore the frequency of landslides in these areas is higher. This study represents the causative factors of the Kodaikanal landslides. Here The landslide inventory map shows that, during the past 10 years, out of 66 landslide incidences, 35 incidences were fallen along the Vatlagundu-Kodaikanal-Palani Ghat roads. Secondly thematic maps were prepared on the various causative factors that is geosystem parameters like geology, lineaments/faults, geomorphology, land use/land cover, drainage system, slope, etc. High resolution Geo-eye satellite data, LANDSAT-TM and ASTER images have been used to generate a few of these thematic maps. To identify the vulnerable areas, the above-mentioned parameters were analyzed in a GIS by assigning appropriate ranks and weights. The result is a landslide hazard zonation map showing regions with varying degrees of vulnerability to landslides. Detailed landslide vulnerability analysis along road corridor. This prepared hazard zonation map will enable to propose and implement suitable mitigating measures, thus preventing loss of life and property in the Kodaikanal hills. An additional study made over landslide vulnerability analysis along road corridor region, using lineament and drainage maps. Though the heavy rainfall is triggering landslides in western-Ghat region, the other causative factors in inducing landslides are anthropogenic activities, geosystem parameters like structure, geomorphology, land use practices, drainage system, etc.

With the increase in impact of landslide disaster to the human life, the government of Sri Lanka took a decision to implement a landslide clearance process in identified landslide prone areas (presently known as landslide risk assessment process). This decision was implemented in March 2011 with the issuance of circular under the Ministry of Disaster Management. National Building Research Organisation (NBRO) was given the authority to issue the landslide clearance certificate for development/ construction in identified landslide prone areas of the country by this circular. Since, landslide disaster has highly impacted on human lives, mapping of landslide hazard areas was initiated in 1989 by NBRO. This landslide hazard zonation mapping project undertook mapping of hazard areas in 1:50,000 scale and 1:10,000 scale. 1:50,000 scale maps covering the entire districts of Matale, Kandy, Nuwara Eliya, Bdulla, Kegalle, Ratnapura and Kalutara are available for the use of planners, developers, decision makers , and general public. As, there are safe slopes areas available within the identified landslide prone districts; government of Sri Lanka took a decision to exempt the safe areas from landslide clearance process. With the implementation of this decision, NBRO was asked to distribute 1:50,000 landslide hazard zonation maps to local authorities, to use them as safe area identification tools. Although, local authorities were given these maps to identify safe areas , it is not clear that whether these maps are really suit for exempting safe areas. This study analyses data from landslide clearance process and landslide hazard maps, and discusses the suitability of landslide maps and finally gives recommendations to the issues identified.