APPLICATIONS OF REMOTE SENSING & GIS IN DISASTER MANAGEMENT
- Space technologies and disaster mitigation communities work together to develop effective and accurate methods for prevention, preparedness and relief measures.
- Disaster prevention is a long-term phenomena that can be best studied with the help of satellite monitoring of various relevant factors such as change in land use.
- Disaster preparedness focusses on warnings and forecasts of impending disasters and entails processes that are dynamic and result in "rapid onset" disasters.
- Disaster relief occurs after (and sometimes during) the emergency.
- Satellite monitoring involves assessment of damage incurred during the disaster.
- Satellite technology helps in identifying escape routes and location for storage of temporary housing.
- Remote sensing and GIS are among the many tools available to disaster management professionals.
- None of the existing satellites and their sensors have been designed solely for observing natural hazards. The spectral bands in VIS (VISible), NIR (Near Infra Red ), IR (Infra Red), SWIR (Short Wave Infra Red), TIR (Thermal Infra Red) and SAR (Synthetic Aperture Radar) provide adequate spectral coverage. This data can be enhanced using a computer and used for effectively managing disasters.
- Repetitive or multi-temporal coverage is justified since the data can be used to study dynamic phenomenon whose changes can be identified over time. For example:
- Natural hazard events
- Changing land use patterns
- Hydrologic and geologic characteristics of a region
- Experts in disaster management:
- Monitor the situation
- Accurately simulate complex natural phenomena and devise better prediction models
- Suggest appropriate contingency plans and
- Prepare spatial databases
- The following are the characteristics of remotely sensed images:
- Spatial continuity
- Uniform accuracy and precision
- Multi-temporal coverage
- Complete coverage regardless of site location
- Use of remotely sensed data:
- Quickly assess severity and impact of damage due to flooding, earthquakes, oil spills and other disasters
- Planning efficient escape routes
- Charting quickest routes for ambulances to reach victims
- Locating places for shelter for victims or refugees
- Calculating population density in disaster prone areas
- Rapidly identifying hardest-hit disaster areas in order to provide early warning of potential disasters.
- Pre-disaster assessments to facilitate planning for timely evacuation and recovery operations during a crisis
- Monitoring reconstruction or rehabilitation after a major disaster
- Developing, maintaining or updating accurate base maps.
Earthquakes: Remote sensing techniques can add to information available through seismic techniques.
- Faults associated with earthquakes can be identified on good resolution satellite imagery.
- Land-use and geological maps give vital pointers towards potential earthquake zones.
- Satellite sensors that are active in VIS (VISible) and NIR (Near Infra Red) spectral bands are useful for the above mentioned purpose.
- IRS, NOAA, SPOT, LANDSAT and IKONOS collect required data. However, LANDSAT imageries are popular as they have a huge historical archive data and are cost effective.
- Earthquakes can trigger landslides of unconsolidated sediments at high elevations.
According to the seismic classification of India, Zone V that covers the following locations is most prone to earthquakes:
- North-East India
- Jammu & Kashmir
- Himachal Pradesh
- Uttarakhand (Due to movement of Indian and Asian plate) and
- Gujarat
Tsunami
- Tsunamis are water waves or seismic sea waves caused by large-scale sudden movement of sea floor. This could be triggered by earthquakes, volcanoes, landslides or man-made explosions.
- Tsunamis can cause serious damage to thousands of kilometers from causative faults.
- They are less than 1m surface height in mid ocean where they originate. They travel at speeds touching 900 kmph.
- As they approach land, the speed decreases and energy is transformed into wave height of almost 25 - 30m
- Time between successive waves is almost 20 to 40 minutes.
- Near the coastline, sea receedes lower than the lowest tide and then rises as a giant wave.
- Satellite or aerial photography when combined with a good GIS database of an area, provides critical information to emergency managers.
Floods : Floods are a result of excess run-off, which could increase or decrease depending upon various factors such as:
- Intensity of rainfall
- Snow melt
- Soil type
- Soil moisture condition
- Land use / Land cover
Every monsoon, some part of India is under floods. In normal rainfall, Uttarakhand, Uttaranchal, Maharashtra & Bengal are flooded.
Flood plains and flood prone areas can be identified on remotely sensed imagery.
Remotely sensed imagery is used for:
- Flood mapping using images of peak flood and post flood
- Flood forecasting based on cloud patterns
For flood mapping purposes, a pre-flood scene and a peak flood image should be compared to delineate the inundated area and based on the land use, classification of the damages in terms of property and crops is established.
The major hurdle in recording floods is that optical satellites cannot penetrate clouds that are present in atmosphere during rainfall.
Optical satellites perform passive remote sensing while Synthetic Aperture Radar (SAR) uses remote sensisng which is
active remote sensing.
Fire:
Fire detection by satellites provides a highly efficient means of detecting and eradicating forest fires without large number of ground based workers.
Thermal Infrared imagery shows 'HOTSPOTS' that may be distinguished from clouds of similar 'Albedo'.
