Landslides in Nilgiris are mainly due to rainfall, but human intervention in the form of deforestation and plantation has turned this into a calamity.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/effect-deforestation-landslides-nilgiris-district
[2] http://admin.indiaenvironmentportal.org.in/category/author/s-vasantha-kumar
[3] http://admin.indiaenvironmentportal.org.in/category/author/v-s-bhagavanulu
[4] http://admin.indiaenvironmentportal.org.in/category/journal/journal-indian-society-remote-sensing
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/land-use
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/nilgiri
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/plantation-crops
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/tea
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/deforestation
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/natural-disasters
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/landslides
[12] http://admin.indiaenvironmentportal.org.in/category/thesaurus/remote-sensing
[13] http://admin.indiaenvironmentportal.org.in/category/thesaurus/tamil-nadu
[14] http://admin.indiaenvironmentportal.org.in/category/thesaurus/rainfall