Geospatial Approach for Delineation of Landslide Susceptible Areas in Karnaprayag, Chamoli district, Uttrakhand, India

Transcription

1 Geospatial Approach for Delineation of Landslide Susceptible Areas in Karnaprayag, Chamoli district, Uttrakhand, India Ajay Kumar Sharma & Anand Mohan Singh

2 Overview Landslide - movement of a mass of rock, debris or earth down a slope due to gravitational force India North-Eastern Himalayas highly prone to landslides come under very high to high hazard zones North-Eastern part of India render to highly landslide prone - Due to the complex geological setup with contemporary crustal adjustment, highly varying relief and ever increasing human interference The landslide susceptibility assessment was carried out based on the combination of maps in a GIS environment, considering the knowledge of local experts (Mariana Madruga de Brito, et.al., 2015). The present paper deals with thematic data layer generation and their spatial analysis in GIS environment for landslide susceptibility mapping

3 Data and Technology used Data Used: Resourcesat 1, LISS III satellite data from Bhuvan Cartosat DEM from Bhuvan GSI Geological Map Technology used: ArcGIS for data integration & analysis ENVI to generate slope aspect, slope degree etc.

4 Methodology

5 Results For Landslide susceptibility mapping, following maps have been prepared using visual interpretation of satellite imagery Lithological Map Geomorphological Map Hydrological Map Soil Type Map Slope Aspect Map Slope Degree Map Structural Map Rock Weathering Map Landslide Map Landuse/Landcover Map

6 Information Value Calculation method Statistical method for spatial prediction of an event based on the parameters and event relationships. The Calculation for Information Value method area as follows: Where, DrA = SiA/Ni (1) NrA = StA / Nt (2) IV = log (NrA/(DrA) (3) DrA = Ratio of active slide area and total study area NrA = Ratio of active slide area and area of a particular unit in thematic map StA = Active Slide Area, Nt = Total Unit Area SiA = Total Active Slide Area, Ni = Study Area IV = Information Value More the total information value the more is the degree of landslide susceptibility.

7 Results Landslide hazard zonation map based on old and active slide S.No Landslide Hazard Zones Active Slide Old Slide 1 Very High Hazard Zone to to High Hazard Zone to to Moderate Hazard Zone to to Low Hazard Zone to to Very Low Hazard Zone < <

8 Results Hazard Zones Very High Hazard Zone Lithology Quartzite, Limestone slate, dolomitic limestone & slate Geomorphology Highly dissected denudostructural hill Slope Degree 45-60, >60 Slope Aspect N-W, N-E, W, N Facing Rock Weathering Moderate to very high Landuse/ Landcover Forest blank, Grass land, degraded land, degraded vegetation, build up area Soil type Loamy soil, Loamy skeletal soil High Hazard Zone Moderate Hazard Zone Slate with quartzite band & unconsolidated sediments Crystalline marble, Thin band of slate, Dolomatic crystalline limestone slate & quartzitic band, Dolomatic limestone & Slate metabascis, unconsolidated sediments Alluvial fans & Flood Plains Moderate dissected denude structural hill 25-35, >60 SW, W Facing N-W, S-W, E & N Facing Moderate Low to moderate Degraded vegetation, medium vegetation Agricultural land, degraded vegetation, build up area Loamy soil, Clayey soil, Loamy skeletal soil Loamy soil, Clayey soil, Loamy skeletal soil Low Hazard Zone Crystalline marble, Thin band of slate, Dolomatic crystalline limestone slate & quartzitic band, Low Dissected denudostructual hill N-E, N-W & E Facing Low to moderate Scrub grass land, Scrub land, Medium vegetation Loamy soil, Clayey soil, loamy skeletal soil Very Low Hazard Zone Quartzite & limestone River Terraces 0-15 Flat, N-W, W, E Facing Nil Barren Land, Dense vegetation, Rocky land Loamy Soil

9 Conclusion Landslide susceptibility evaluation involves a high level of uncertainty due to data limitations and model shortcomings The accuracy of susceptibility assessment is lower, when different types of slope movement are considered as a whole, because those landslides may have different spatial incidence, and distinct threshold conditions concerning preparatory factors This difficulty may be resolved by defining types of landslides prior to the susceptibility assessment. Different types of landslides are not equally conditioned by the instability factors. Information value scores show that lithological unit is the main preparatory condition for rotational movements Shallow translational slides have the strongest spatial correlation with slopes with gradients higher than 25

10 Conclusion In any event, different types of landslides neither have the same magnitude nor equal damaging potential. Deeper and larger slope movements (rotational and translational) may produce serious damage to properties and structures, while shallow translational slides are only responsible for minor road disruptions. The technical strategies to mitigate landsliding also depend on landslide typology. These are additional reasons to discriminate between different types of slope movements when assessing landslide susceptibility and hazard.

11 Discussion/ Q&A

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