19 September 2018
Kodagu landslides in Karnataka, India: Planet Labs imagery
On 15th to 17th August, the Kodagu area of Karnataka in SW India suffered exceptional monsoon rainfall, inducing floods and landslides. Reports suggest that over 200 mm fell per day on three successive days. There were many fatalities and a high level of damage was inflicted. There has been considerable controversy in India as to the cause of the Kodagu landslides, with suggestions ranging from environmental degradation, release of water from a network of dams and even a previous earthquake. A team has been established to examine the causes; it will be interesting to see what they find.
These landslides received comparatively little attention in outside of India, but they were a very substantial event. Raj Bhagat P and Samrat Basak from WRI India, used Copernicus Sentinel data to examine the impact of the landslides.The Planet Labs image below shows the heart of the area affected by the landslides, prior to the event (image from 11th May 2018) – this is an area of forest with some human modification for farms and roads. It is hilly, but not mountainous:-
Compare that with the PlanetLabs image below, collected on 15th September 2018:-
The difference is dramatic – it is clear that many landslides were triggered across this area. These look to be shallow slides that have transitioned into channelised flows. In many cases multiple landslides have coalesced into the same channel. The area below is such an example:-
Each of the channels here has been fed by multiple smaller landslides, forming very dramatic channelised flows. There is extensive sediment deposition on the valley floor, which will have been disastrous for the farmers in this area. The reports of the loss of infrastructure is explained, at least in part, by the extremely damaging effects of these flows.
Acknowledgement and Reference
Kishor Cariappa first highlighted the extensive nature of these landslides, as evidenced by satellite imagery, on the website Kodagu Connect. Interpretation of satellite images of this event was first undertaken by WRI India, using modified Copernicus Sentinel data ; Processed by Raj Bhagat P, Samrat Basak.