Landslide Forecasting and Warning Mechanism

Transcription

1 Annual Conference of Relief Commissioners, Disaster Management 18 May 2018, Vigyan Bhawan, New Delhi Landslide Forecasting and Warning Mechanism Dr. Saibal Ghosh Director, GSI, New Delhi Understanding landslide Landslide - an individual phenomena Causes are complex and non-linear Each landslide is unique An event can trigger one or many landslides Inventoried active landslides are many 2 1

2 Society vs Landslide Viewed as an individual problem Ignorance/lack of awareness Less priority due to other societal obligation Society accepts the risk and live with it Makes Society more vulnerable 3 Landslides: Indian Scenario 1.4 lakh sq. km. 1.0 lakh sq. km. 1.8 lakh sq. km 116 Districts 366 Taluks Villages/ Settlements lakh sq. km. is landslide prone (12.6% of the Indian landmass) 2. Varied geo-environments & varied failure mechanisms 3. India contributes to about 8% of global landslide fatalities 4 2

3 Can we forecast a landslide? Theoretically YES.. for an individual landslide Prediction through instrumentation highly cost intensive there are thousands of active landslides!!! CHALLENGE for a large area & new failures Conditions and slopes conducive for landsliding Pin Pointing the event in space and time rainfall threshold modeling 5 What vital information we have (GSI s National Landslide Susceptibility Mapping Project) Total NLSM Target = 4.2 lakh sq. km Priority 1 = 2.8 lakh sq. km Priority 2 = 1.4 lakh sq. km (highly inaccessible and high-altitude areas) Priority 1 already completed till March 2018 = 1.71 lakh sq. km (61%) Priority 2 already completed/ data acquired = sq. km. (49%) Project Completion = March 2020 Data already uploaded in public domain = 70,000 sq. km. Data to be uploaded by June 2018 = another 49,000 sq. km. Landslide polygons already mapped = ~ 30,000 Landslides detailed attributes updated from field = ~ 13,

4 Landslide EWS model No out-of-the-box system available. Villages located in remote areas and landslides occur at night. Effective EWS needs four inter-related key elements: (1) risk knowledge; (2) monitoring, analysis and warning; (3) dissemination and communication; & (4) preparedness for timely response. Making the four interrelated key elements of EWS to function in sync across all sectors seems quite challenging 7 The communication of daily rainfall to BDMO/DDMC can be via telephone or Short Messages Service (sms) or WhatsApp group. The message text here may be Limbhudhura raingauge rainfall 15.2 cm on 12 Sept. 8 4

5 People-Centric L-EWS Community Science (1) risk knowledge (2) monitoring (3) analysis and warning (4) communication (5) preparedness 1. Preparation of rainfall threshold. 2. Selection of villages for L-EWS. 3. Awareness generation through CBDMP. 4. Communication through billboards and contact programmes. 5. Integration and development of L-EWS model with the local level participation. Kurseong and Mirk subdivisions of Darjeeling district, WB 9 Selection of villages 1. Selection of village clusters based on the available macro-scale landslide susceptibility maps (NLSM). 2. Selection of villages based on landslide vulnerability and discussion with the local administration. 3. Data collection through risk assessment survey for the selected villages. Selected two villages based on risk assessment study for development of L-EWS model 10 5

6 Total villages/clusters 50 villages Step-1 16 villages Step-2 06 villages Step-3 02 villages 11 Transfer of Risk knowledge Landslide awareness The aim was to convey the findings of landslide risk assessment to impart a basic knowledge on L-EWS and also the risk scenarios at local levels. a. Learn, b. Monitor, c. Interaction and demonstration, d. Maintain and e. Report. 12 6

7 5/6/2018 Transfer of Risk knowledge 7

8 Monitoring, Analysis & Warning Day Daily rainfall (cm) Amount of rainfall required for ALERT warning Amount of rainfall required for ALARM warning Day So the Day-4 needs 15.6 So the Day-4 needs 17.6 cm of Day-2 6 cm of rain for ALERT rain for ALARM warning. Day-3 The communication 2 warning. of daily rainfall to BDMO/DDMC can be via telephone or Short Day-4 Messages If the area Service is having (sms) forecast WhatsApp of heavy group. rainfall, The message then six hourly text here rainfall may data be is to be measured Limbhudhura and before raingauge reaching rainfall the15.2 cumulative cm on 12 rainfall Sept. to 15.6 cm/17.6 cm, an ALERT/ALARM is to be issued accordingly. 15 Conclusions 1. Regional L-EWS though challenging, can be attempted provided - A bottom-upward approach is followed involving local community from the very beginning Close spaced rain gauge network in hills is prerequisite The communication of daily rainfall to BDMO/DDMC can be via telephone or Short Messages Service (sms) or WhatsApp group. The message text here may be Similarly rainfall forecast models of higher spatial resolution Limbhudhura raingauge rainfall 15.2 cm on 12 Sept. can definitely improve such models further. 2. Use of landslide susceptibility maps is a must for planning and designing all infrastructure projects in landslide prone areas 16 8

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