Studies on land disturbances due to soil piping affecting the critical zones in Western Ghats of Kerala (A project funded by the Kerala State Disaster Management Authority) Final Report Submitted to State Disaster Management Authority Government of Kerala ESSO-National Centre for Earth Science Studies (Ministry of Earth Sciences, Govt. of India) Thiruvananthapuram 695011 January 2020 Studies on land disturbances due to soil piping affecting the critical zones in Western Ghats of Kerala (A project funded by the Kerala State Disaster Management Authority) Final Report Submitted to State Disaster Management Authority Government of Kerala ESSO-National Centre for Earth Science Studies (Ministry of Earth Sciences, Govt. of India) Thiruvananthapuram 695011 January 2020 Studies on land disturbances due to soil piping affecting the critical zones in Western Ghats of Kerala (A project funded by the Kerala State Disaster Management Authority) Project team G. Sankar Senior Consultant Dr. D. S. Suresh Babu Principal Investigator Midhun T. M. Project Scientist (2017-19) Sarath Kumar Project Scientist (2016) January 2020 ESSO-National Centre for Earth Science Studies Thiruvananthapuram 695011 DOCUMENTATION PAGE NATIONAL CENTRE FOR EARTH SCIENCE STUDIES 1. REPORT NUMBER NCESS-PR-01-2020 2. TYPE OF REPORT PROJECT FINAL REPORT 3. TITLE STUDIES ON LAND DISTURBANCES DUE TO SOIL PIPING AFFECTING THE CRITICAL ZONES IN WESTERN GHATS OF KERALA G. Sankar, D. S. SureshBabu, 4. AUTHORSHIP T. M. Midhun, Sarath Kumar 5. KEY WORDS Land disturbance, Soil Piping 6. ABSTRACT Western Ghats often experiences flooding, mass-movements in the form of landslides and land- subsidence. Studies conducted by NCESS revealed that land subsidence is often due to a process occurring in the subsurface known as soil piping or tunnel erosion. Land disturbances due to soil piping are noticed in all districts in Kerala except Kollam and Alappuzha. In 2016 NCESS in collaboration with SEOC has completed a 3 years long study funded by the NDMA, GoI on soil piping related problems in the State. This study has been carried out as a follow up of the NDMA funded programme. NCESS has identified more than 139 regions in the Western Ghats severely affected by soil piping. A detailed field related study to demarcate areas affected was needed to know the extent of damages occurred due to soil piping. This project was taken up to fulfill some of the missing aspects in the NDMA funded programme. The critical zone in the Western Ghats which is the permeable near surface layer from the top of the trees to the bottom of the saturated zone is a very important layer where various geo environmental parameters interact. This zone is very often subjected to changes by many processes such as anthropological activities, neo-tectonic activities, natural hazards etc. during high rainfall seasons like monsoons. It is recommended that site-specific and detailed studies are required to understand the soil piping affected areas in the state for proposing mitigation plans at each affected location. In the affected areas the laterite mining should be discouraged or the depth of the mine to be restricted 1m above the lithomarge clay. In no case the clay should be mined or exposed. It is recommended that usage of hydrated Lime along with the fertilizers should be encouraged to neutralise dispersive sodium in the clay at the already affected localities. Major developmental projects should be taken up in highlands only after proper geologic / geophysical studies to rule out existence of subsurface tunnels. The soil survey department may take proper initiatives to determine the areas where dispersive soils are present in the State. The areas where earth dams are present in the state should be watched closely to rule out the presence of dispersive soils. Since dispersive soils are located nearby the Banasurasagar Dam in the Wayanad district, the location should be supervised carefully for any possible soil piping erosion. Dewatering is the best method to deescalate the formation of soil pipes. Overland flow may be diverted to a nearby nala / stream without allowing to infiltrate the affected zone will reduce pipe development. 7. DISTRIBUTION STATEMENT FOR LIMITED CIRCULATION 8. INSTITUTION NATIONAL CENTRE FOR EARTH SCIENCE STUDIES ESSO, MINISTRY OF EARTH SCIENCES, GOVERNMENT OF INDIA P.B.NO,7250, AKKULAM, THIRUVANANTHAPURAM-695011 Phone: 0471-2442454 Fax: 0471-2442280 Acknowledgements This project is a follow up project of the project “Studies on the soil piping in the Highlands and Foothills of Kerala to avoid the disaster” funded by NDMA and carried out in collaboration with SDMA by NCESS in 2016. The Project Team expresses profound thanks to all those, who have directly or indirectly helped in the successful completion of the project. First of all, we thank the Director, NCESS Dr Purnachandra Rao for his constant support to this programme. The investigators also express their sincere thanks to Dr Sekhar Kuriakose, Head, SEOC and Member Secretary KSDMA, Govt. of Kerala for his encouragement and keenness in the project. Dr. D.S.Suresh Babu, Scientist-F, NCESS is thanked for giving all the administrative support for the research team. He is the main force behind the successful completion of the National workshop and field training on soil piping held in NCESS during 6-8 July 2017. The project team thank SDMA for funding the Project and recognised the importance of this pilot study. All the staff members of the mitigation team of SDMA are thanked for their sincere support and encourage given to this project. Dr S. Venu IAS, Additional Chief Secretary, Revenue & DM department is thanked for his patronage and support. The staff members of SEOC, Revenue and Disaster Management department is thanked for their valuable support at various stages of implementation. The support given by Shri Pradeep, Hazard Analyst, SEOC is duly acknowledged. The village, taluk and the district administration had helped this team by providing data of new events. The project team would like to thank fellow researchers and staff members of NCESS, without their cooperation it would not have been possible to successfully complete this work. The help rendered by Sri Prasobh. P Rajan, Project Assistant CrP is specially thanked for contributing to this work continuously. Sri Eldhose K helped this team in carrying out electrical resistivity Surveys. Smt. Panjami, Asst Professor, Department of civil Engineering FISAT is thanked for the geotechnical studies carried out for this project. G Sankar Senior Consultant (2016-18) For the Project Team I Contents Page no. 1. Chapter -1 Problem statement 1 1.1. Soil piping or tunnel erosion: definition, Formation 2 1.2. Literature survey 4 1.3. Previous studies 15 2. Chapter -2 Objectives and Methodology 16 2.1. Classification of soil pipes 17 2.2. Classification of study area 20 3. Chapter- 3 Soil piping affected areas in Kerala 22 4. Chapter- 4 Soil piping in the state-district wise analysis 33 4.1. Kasaragod 33 4.2. Kannur 63 4.3. Malappuram 78 4.4. Wayanad 99 4.5. Idukki 109 4.6. Thrissur 136 4.7. Kozhikode 146 4.8. Palakkad 155 4.9. Pathanamthitta 163 4.10. Ernakulam 170 4.11. Thiruvananthapuram 177 4.12. Kottayam 185 4.13. Kollam 190 4.14. Alappuzha 196 4.15. Soil piping Hazard Zonation of the State 202 5. Chapter- 5 Geotechnical Investigations and Mitigation work 205 6. Chapter- 6 Conclusion 216 7. References 222 II List of Tables Table 3.1 Soil piping affected Districts in Kerala Table 3.2 Location details of the soil pipes reported Table 4.1 piping locations in Kasaragod District Table 4.2 Areal extent of soil piping affected regions, Kasaragod Table 4.3 piping locations in Kannur District Table 4.4 Areal extent of soil piping affected regions, Kannur Table 4.5 piping locations in Malappuram District Table 4.6 Ground investigation details, Klari, Malappuram Table 4.7 Areal extent of soil piping affected regions, Malappuram Table 4.8 piping locations in Wayanad District Table 4.9 Areal extent of soil piping affected regions, Wayanad Table 4.10 piping locations in Idukki District Table 4.11 Analytical report of soil samples, Idukki Table 4.12 Major element data of samples from piping location, Idukki Table 4.13 Exchangeable sodium, calcium, magnesium of piping location, Idukki Table 4.14 Textural analysis of soil samples, Idukki Table 4.15 Peak list of soil samples, 1A Idukki Table 4.16 Peak list of soil samples, 2A Idukki Table 4.17 Peak list of soil samples, 4A Idukki Table 4.18 Peak list of soil samples, 5A Idukki Table 4.19 Peak list of soil samples, 5B Idukki Table 4.20 Peak list of soil samples, 5C Idukki Table 4.21 Peak list of soil samples, 5D Idukki Table 4.22 Peak list of soil samples, 5E Idukki Table 4.23 Estimation of major elements by XRF and Calculated CIA Table 4.24 Areal extent of soil piping affected regions, Idukki Table 4.25 piping locations in Thrissur District Table 4.26 Areal extent of soil piping affected regions, Thrissur III Table 4.27 piping locations in Kozhikode District Table 4.28 Areal extent of soil piping affected regions, Kozhikode Table 4.29 piping locations in Palakkad District Table 4.30 Areal extent of soil piping affected regions, Palakkad Table 4.31 piping locations in Pathanamthitta District Table 4.31 Areal extent of soil piping affected regions, Pathanamthitta Table 4.32 Piping locations in Ernakulam District Table 4.33 Areal extent of soil piping affected regions, Ernakulam Table 4.34 Piping locations in Thiruvananthapuram District Table 4.36 Areal extent