Drones to generate flood inundation models in Guntur (other cities should take a cue)


For many years now, Guntur (Andhra Pradesh) has been at the mercy of heavy rainfall and flash floods. During a 24-hour period between September 21 and 22, Machilipatnam, a city in Krishna District, recorded 117 mm of rain. Between September 23 and 24, Dachepalli in Guntur recorded 171 mm of rain, and in Pulipadu around 155 mm.

Since the traditional approach for surveillance or mapping involves manpower, areas that are flooded or inundated are inaccessible at times or very difficult to survey. In this connection, the Andhra Pradesh Government decided to utilise civil unmanned air craft systems [especially drones] for real-time governance to enable effective and efficient service delivery to the citizens. As part of this initiative, ideaForge was approached to engage its drone (UAVs), to provide end-to-end services for flood inundation modelling. ideaForge deployed its VTOL NETRAv2 drone above the town of Guntur to assess and simulate the damage that took place after the area experienced above average or heavy rainfall.

The project’s main aim: Produce a high-resolution photographic simulation of the town’s surrounding geography and terrain at progressing levels of flooding, and asses the area of land that could be affected or would be inundated.

How it works
ideaForge’s flagship product, NETRAv2 offers huge advantages over conventional methods of inspection, monitoring, surveillance and mapping. It can be utilised in every part of geospatial studies including exploration, planning, mapping, operation, inspection and reclamation. Since NETRAv2 has a long endurance and long range, it allows the user to cover a large area at higher altitude. Images captured by UAVs span thousands of hectares of land in a single flight without the cost and hassle of manned services. The images produced are also of far greater quality than that of the satellite imagery.

After processing the images, they are transformed collectively into one large ‘geo referenced orthomosaic’ image, which helped in creating efficient plans resulting in better decision making capabilities for site planning engineers, generate detailed modelling and imagery of topography resulting in better management, model geophysical & watershed or catchment areas and monitor and report progress.

Along with the mapping of inundation, the project used the NETRAv2 drone to monitor the crops in the area. Using the drone fitted with sensors that can capture infrared spectrum, large expanses of field were monitored to estimate the effect the flooding had on the crop health. One of the prominently used indices is Normalized Difference Vegetation Index (NDVI), which measures the degree of vigour of the plant. This provides enough information to produce conclusions surrounding the soil quality, nutrition and other environmental factors. Once the map reflectance of NDVI is generated, analysis can determine areas that had severe crop damage due to the flooding, from leeching of minerals and soil erosion.

The project proved UAVs to be extremely successful and useful in completing aerial surveys for disaster-hit areas. NETRAv2 produced incredibly high quality data in a cost-effective manner, in a short span of time. The project also demonstrated the flexibility of aerial platforms, and specifically demonstrated NETRAv2’s all-terrain performance capability.

The project produced the following results:

  • The highly-affected areas were surveyed and recorded.
  • Areas that experienced sedimentation, water logging and soil and land damage were identified and recorded.
  • Mapping and analysis provided information on impact on residential, commercial and agricultural areas.
  • The high quality and clarity of images helped identify possible rescue locations for future flooding rescue and relief operations.
  • Aerial images helped identify fields impacted for government authorities to plan for compensation.
  • The information can be used for effective water management.
  • The processed images can be used for watershed, drainage basin & water flow mapping.
  • The analysis of data over a period can help identify flood patterns and help the government plan future infrastructure projects, drainage systems, land allotment and others accordingly.
  • Recording of flood patterns will also help agriculture, mining and other industries implement preventative measures in respect to cropping, mining and others.

The Andhra Pradesh State Fibernet Ltd (APFSL), alongwith the Andhra Pradesh Government, can now use the maps for urban planning. The data will also help pinpoint the areas in Guntur that require measures to prevent future flooding. The amount of detail will also assist government bodies in identifying suitable areas for the implementation of proper drainage systems. In a worst-case scenario, if the area faces future destructive flooding, the mapping will be a source of information for the government, in providing flood relief funding. In conclusion, the flood inundation modelling proved to be a successful project, and will hopefully provide enough data for the government to act in respect to a future flood crisis. Flood-prone cities like Mumbai can take a cue from the Andhra Pradesh Government.