Landslides kerala context

A study on lanslides & a case study from kerala

1. LANDSLIDES Submitted By - Mohammed Jasir ( Roll no 24) - Merin Mariya George (Roll no 23)

2. LANDSLIDES A landslide is defined as the movement of a mass of rock, debris, or earth down a slope. Also known as Landslips or Slope failures

3. REASON Slope movement occurs when forces acting down-slope (mainly due to gravity) exceed the strength of the earth materials that compose the slope

4. CAUSES Due to the verge of - Movement by rainfall Snowmelt Changes in water level Stream erosion Changes in ground water Earthquakes Volcanic activity Disturbance by human activities Vibrations from machinery, traffic, blasting and even thunder may trigger failure of weak slopes In shallow soils, the removal of deep-rooted plants can cause failure of slopes or any combination of these factors.  Earthquake shaking and other factors can also induce landslides underwater. These landslides are called submarine landslides. Submarine landslides sometimes cause tsunamis that damage coastal areas. 

5. TYPES Common types are Rotational & Translational landslides

6. Types of Landslides FALLS Falls are sudden movements of loads of soil, debris, and rock that break away from slopes and cliffs. Falls landslides occur as a result of mechanical weathering, earthquakes, and force of gravity.

7. Types of Landslides, cont…. SLIDES This is a kind of mass movement whereby the sliding material breakaways from underlying stable material. The kinds of slides experienced during the type of landslide like rotational and transitional. Rotational slides are sometimes known as slumps since they move with rotation. Transitional slides consist of a planer or 2 dimensional surface of rupture . They involve landslide mass movement following a roughly planar surface with reduced rotation or backward slanting. Slides occur when the toe of the slope is undercut. They move moderately, and the consistency of material is maintained. Translational Rotational

8. TOPPLES Topple landslides occur when the topple fails. Topple failure encompasses the forward spinning and movement of huge masses of rock, debris, and earth from a slope . This type of slope failure takes place around an axis near or at the bottom of the block of rock Types of Landslides, cont….

9. SPREADS They are commonly known as lateral spreads and takes place on gentle terrains via lateral extension followed by tensile fractures. FLOWS This type of landslide is categorized into five; earth flows, debris avalanche, debris flow, mudflows, and creep, which include seasonal, continuous and progressive . The most prevalent occurring landslides are rock falls and debris flow. Types of Landslides, cont….

10. Kuranchery landslide Kerala 2018

11. A portion of a hill on the Machad forest range came down in the landslide around 6.45 a.m. on August 16 and washed away four houses killing 19 people . “It happened like a bullet shot. Along with the hill, water, rocks and uprooted trees came down the hill . according to the officers of geology department who inspected the area, a portion of the soil above huge rocks came down after water percolated into the soil in three days of relentless rain . As many as 20 earth movers and the same number of tippers took part in the rescue operation that went on for three days from August 16.

12. Clause from Post disaster assessment study report by kerala govt.Disaster management board Many of the landslides that occurred during the first two weeks of August 2018 brought down a considerable portion of the mountainside. these slides will continue to creep upslope as the precipitation and instability of the slopes continue.

13. Mitigation measures Land Assessment. Slope Stabilization and Development Prepare Slope Stability Maps Prepare Landslide Inventory Database. Redirect Debris Channel . Vegetation Dewatering Soil Reinforcement

14. Kerala Post Disaster Needs Assessment Floods and Landslides - August 2018 issued on FEB 2019

15. PRECAUTIONARY MEASURES The natural drainage shouldn’t be disturbed or blocked on the slope. Water shouldn’t be allowed to accumulate or percolate on the slope. For support wall, wider base and slightly incline (towards hill) are to be provided. Weep holes are must Weep holes should weep. This can be achieved with proper backfilling i.e. coarser material at the bottom and successive finer layer . Care should be taken for anything that may move/fall downward. Exposing a very high vertical face should be avoided. Avoid adding load very close to the edge of the slope.

16. PRECAUTIONARY MEASURES, cont … The review and revision of the building rules for urban and rural areas needs to be prioritised . Update the existing land-use maps with respect to the multi-hazard map . Make landslide-hazard zonation maps available in a scale appropriate for planning at the local level (1:5,000 at least) for all municipalities and panchayats in the hill zone . Initiate a major shift in land-use policies demarcating certain areas as ‘no development zone’ and ‘construction restricted zone’. Appoint geologists in all municipalities and panchayats in the hilly regions to ensure adequate technical support to the regulatory authorities for enforcement of the building rules People may be incentivized to move from hazardous zones to safety . Disincentives could be in terms higher taxes or ineligibility for any relief or compensation in the event of future natural hazards.

17. PRECAUTIONARY MEASURES, cont … Where resettlement is needed, the government should also explore the transfer of development rights (TDRs), with the government acquiring lost/ hazard-prone land, at market rates to ensure that the vulnerable locations are not encroached upon in future . Resettlement compensations can be adapted from the existing Rehabilitation and Resettlement (Kerala) Rules 2015

18. PRECAUTIONARY MEASURES, cont …

19. A view of Kavalappara , in Pothukal panchayath Kerala 2019

20. A view of Puthumala at Meppadi panchayatpanchayat Kerala 2019

21. After effects  Economic Decline Landslides certainly cause damage to property . This brings losses to the economy of a country. Economic rehabilitation is also needed in the area that has experienced a landslide. This would cost a lot and some of the offending country economy. Damage To Infrastructure. Landslides can lead to damage to property resulting from the force flow or mud. Infrastructure land such as buildings, roads, places of leisure and so on can be destroyed by the landslide occurred. Loss Of Life. Loss of life is a dangerous effect upon the occurrence of a landslide and it is difficult to avoid. Many lives will be lost upon the occurrence of landslides

22. After effects, cont… Changes In The Surface Landscape. Landslide causes significant changes in the landscape of the earth's surface. Pile of soil and mud from the landslide activity caused the high ground may be flat and settling sediment can become thick very quickly . Consequently, dam rivers or lakes become more shallow to hold a lot of water.  Water level becomes higher and the ground becomes waterlogged areas Landslides can also cause soil or rock slope becomes increasingly steep and unstable Effects on Fauna Although most kinds of wildlife are able to retreat fast enough to prevent direct injury from all but the fastest-moving landslides, all wild creatures are subject to habitat damage and destruction. Fish are probably most affected because they depend on stream access and water quality for their livelihood, both of which are commonly influenced in the short term by landslides.

23. METHODS – in short Landslide hazard, vulnerability, and risk assessment Multi-hazard conceptualization Landslide remediation practice Research and development, monitoring and early warning Knowledge network and management Capacity building and training Public awareness and education Emergency preparedness and response Regulation and enforcement DISASTER MANAGEMENT

24. Puthumala and kavalappara are warning signs. If we fail to act now, catastrophic disasters will wipe the state off the map MADHAV GADGIL