Due to its diverse geo-climatic conditions and on account of it being an intertropical convergence point, India witnesses recurring tsunamis, floods, cyclones, droughts, landslides, and earthquakes every year. A report titled Human Cost of Disasters by the United Nations Office for Disaster Risk Reduction (UNDRR) states that 79,732 people lost their lives and 1.08 billion people were affected by 321 natural calamities in India over the course of 20 years (1999-2019). Further, the country suffered economic losses of $79.5 billion from 1998-2017, according to a UNDRR report titled Economic Losses, Poverty and Disasters.
However, technological developments in the field of Earth Observation (EO) are now helping incubate both new imagination and ever more powerful applications of geospatial technologies in managing disasters.
Data obtained from meteorological satellites is used to track cyclones, asses their intensity, make landfall predictions, and forecast extreme weather events. This data is then used for monitoring disaster events and assessing damages. The main responsibility for providing guidance to ACWCs (Area Cyclone Warning Centres) for issuing cyclone warnings lies with the Indian Meteorological Department (IMD).
EO satellites used by IMD:
“RSMC (Regional Specialized Meteorological Centre) at New Delhi issues cyclone advisories every three hours to 13 countries in the WMO-ESCAP Panel,” a senior IMD official told Geospatial World. He added that satellite data is now the single most important component of the Global Basic Observing Network (GBON) for Numerical Weather Prediction (NWP). The GBON paves the way for a radical overhaul of the international exchange of observational data, which underpin all weather, climate and water services and products.
The improvement in the quality of satellite data and assimilation techniques in the numerical models over the years has brought significant improvement to the quality of forecasting instruments.
The official noted that through the use of the Global Hydro-Estimator (GHE) and MicroWave adjusted Global Hydro-Estimator (MWGHE) — both products of the National Oceanic and Atmospheric Administration (NOAA) — in the recently operationalized South Asia Flash Flood Guidance System, significant improvements were made in assessing the hydro-meteorological parameters required for generating flash flood guidance to the South Asian member countries.
On the advantages of using satellite observations, he said the satellite observations include filled observational gap over large oceanic areas, (which are otherwise inaccessible), are continuously monitored through polar (twice daily) and geosynchronous (half hour or less) satellites. An observational gap is a time during which observations are suspended while either other operations are performed or when there is no spatial scope to cover it.
These observations provide an added advantage to meteorologists during the process of weather forecasting. Derived products like Cloud Motion Vectors (CMVs), Outgoing Longwave Radiation (OLRs), and Sea Surface Temperature (SST) are important parameters to observe various weather phenomena like monsoons, thunderstorms, fog, etc.
According to experts, the intensity of severe cyclonic storms occurring in the North Indian Ocean has increased in the past four decades, owing partly to global warming. While almost all states lying on India’s coastal regions are prone to cyclonic activity, Odisha, West Bengal, Andhra Pradesh, Tamil Nadu, Kerala, Maharashtra, and Gujarat are most impacted by them.
Odisha alone is exposed to cyclonic storms almost every year. Most recently, it was affected by the cyclone Yaas, which made landfall in May 2021 and was the 96th tropical cyclone to hit the state in 130 years. P.K. Mallik, Chief Executive, Odisha Space Application Centre (ORSAC), explained that for Odisha, the National Remote Sensing Centre (NRSC) under the Department of Space provides maps of flood inundated areas to the Special Relief Commissioner, Government of Odisha, and the defense personnel engaged in relief and rescue operations. “NRSC provides damage assessment maps related to crop loss, infrastructure loss, etc., to various departments for effective damage control action by the government,” said Mallik.
Pre-disaster datasets are regularly used by state departments, the Special Relief Commissioner (SRC), and the Odisha State Disaster Management Authority (OSDMA) for awareness, evacuation planning, relief preparatory activities, and other resource allocation purposes. Mallik explained that the state administration used satellite images generated by the Department of Space, Government of India, and derived flood layer datasets of the state during the Fani, Amphan and Yaas cyclones. The flood layer datasets were generated using near real-time satellite that passed over the area during the disasters. Various satellites from India and other countries (such as RADARSAT of Canada) were used for generating these flood layer datasets of disaster affected areas in the quickest possible time and sent to state nodal centers, the Special Relief Commissioner and OSDMA. The flood area datasets received by SRC, OSDMA and ORSAC online were connected to a map format with a projection system and scale. The achieved digital vector data available at state centers (block/village boundary, settlement, road, rivers/permanent water bodies, etc.) were overlaid on the flood layer data and flood maps were generated along with gross statistical estimation of the submerged areas.
Mallik said, “ISRO (Indian Space Research Organization) provided satellite derived outputs to ORSAC during the Fani, Amphan and Yaas cyclone periods. The satellites that provided the vital data were Sentinel-1A SAR, Sentinel-2A SAR, IR/ESA satellite images, Sentinel-1A and TerraSAR-X Satellite images.”
According to research by the Asian Development Bank, floods account for more than half of climate-related disasters in India and have cost the country well over $50 billion since 1990. The country has experienced a total of 278 floods in the span of 20 years (1980-2018), affecting more than 750 million people.
Prof. Mahendra Bisht, Director, Uttarakhand Space Application Centre (USAC), cited the usefulness of satellite data in helping quickly identify the zones of active hazards, particularly in the mountainous terrain of Uttarakhand. This data, along with saving time, helped in search and rescue operations. “The data helps us to identify potential hazard zones, namely landslides, creeping zones, Glacial Lake Outburst Flood (GLOF) features, and active forest fire areas. Very high resolution (VHR) data also provides us with information to find out diseases in crops as well as crop estimations,” said Bisht.
“In the aftermath of the February 7, 2021 Dhauliganga disaster, an international charter was invoked for assessing satellite data from various sources. USDMA was provided interpretations pertaining to damages caused and the cause of the floods, together with results of continuous monitoring of the lake formed during this event on Rishiganga,” he added.
According to Prof. Bisht, “Initially, the data provided by ISRO was only from LISS IV and CartoSAT. Later, we purchased VHR data from Maxar. The satellites that provided this information were Cartosat, IRS, WorldView and IKONOS.”
Dr. Piyoosh Rautela, Executive Director, Disaster Mitigation and Management Centre (DMMC), said the Uttarakhand State Disaster Management Authority (USDMA) is using satellite data for generating Digital Elevation Models (DEM) to study terrain characteristics; create landuse/landcover maps; create base maps for field studies and other mapping purposes; conduct hazard, risk, and vulnerability studies; and carry out landslide investigations.
Dr. Rautela said that during the recent mishap that occurred on February 7, 2021 at Rishiganga, a huge mass of ice and rock flowed and caused heavy destruction at Reni village and Tapovan hydro project site, killing at least 200 workers. At that time, USAC was able to help the state authorities by providing first-hand information through high resolution satellite data procured from NRSC Hyderabad.
In August 2018, 13 of Kerala’s 14 districts witnessed severe flooding, affecting 1.3 million people. According to reports, the state could not calculate the severity of the flooding because it did not have any information system to effectively manage the crisis. At that time, EO data from optical (Worldview-3, Sentinel-2) and SAR (Sentinel-1) satellites was used to analyze the flood event. However, to understand flood progression and recession, the multi-temporal Level-1 Ground Range Detected (GRDH) Sentinel-1 SAR images that were acquired before, during and after the heavy rainfall were used. The analysis proved to be helpful in flood mitigation measures and in the preparation of contingency plans for future flood events.
With climate change showing its effect in the form of more severe natural disasters, EO data has been providing vital information to scientists and is helping them gain comprehensive understanding of the Earth from Space. And as advanced tools and machineries are developed, new satellites are launched every year with advanced functionalities and data collection tools, so that scientists can make more informed decisions and help save lives during major mishaps.
According to ISRO, India has plans to launch three more satellites by the end of 2021, which will further earth observation and, in turn, provide qualitatively and quantitatively better satellite-derived data for disaster mitigation.