National Remote Sensing CentreIndian Space Research Organisation

Dept. of Space, Govt. of India

Annual Flood Inundation

http://bhuvan.nrsc.gov.in

National Remote Sensing CentreIndian Space Research Organisation

Dept. of Space, Govt. of India

Hyderabad-500 037

January 2012

Annual Flood Inundation – Assam and Bihar

http://bhuvan.nrsc.gov.in

National Remote Sensing Centre

Assam and Bihar

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Document Control Sheet

Document Number NRSC-RS&GISAA-DMSG-DMSD-JAN.,2012-TR-374 Title Technical Note on Annual Flood Inundation Layers

Type of Document Technical Report-Ver.1 Number of Pages 5

Author(s) DMSD,DMSG Reviewed by Group Head, DMSG Approved by DD (RS&GIS-AA), NRSC

Abstract Information on flood affected areas is important for planning relief activities. Decision Support Centre (DSC), DMSD, NRSC kept a constant watch on the flood situation in the country and major floods were mapped and monitored using satellite remote sensing data. The flood inundation layer was delineated from optical and microwave satellite data by applying suitable classification techniques. About 13 years (during 1998-2010) of annual flood inundation layers were prepared by integrating different flood waves in a calendar year. This document briefly explains the methodology adopted in the generation of flood inundation layers for Assam State.

Controlled by Head, DMSD Distribution Unrestricted

Reproduction Rights The report and its contents are the property of National Remote Sensing Centre (NRSC)/ISRO.

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ANNUAL FLOOD INUNDATION LAYERS

INTRODUCTION Flood is one of the most severe disasters affecting the people across the globe. India is the worst flood-affected country in the world after Bangladesh and accounts for one-fifth of global death count due to floods. Nearly 75 per cent of the total Indian rainfall is concentrated over a short monsoon season of four months (June-September). As a result, the rivers witness a heavy discharge during these months, leading to widespread floods. About 40 million hectares of land in the country is liable to floods according to National Flood Commission, and an average of 18.6 million hectares of land is affected annually. The annual average cropped area affected is approximately 3.7 million hectares. The most flood-prone areas in the country are the Brahmaputra, Ganga and Meghana River basins in the North and North-east India. Though flood is an age-old phenomenon and cannot be stopped, its damages can be minimized by proper flood plain management measures. Flood disaster management demands efficient planning measures, implementation and policy making decisions, application of modern scientific and communication tools for smooth functioning of the system. For effective flood management, the concerned flood control departments require information on the spatial extent of the affected area for taking decisions on the relief and rescue operations that need to be carried out immediately and a flood inundation map helps the decision-maker to make a scientific assessment for better management of relief activities. In this context, satellite remote sensing plays an important role in delineating flood affected areas. Satellite remote sensing from their vantage position has unambiguously demonstrated their capability in providing important information and services for flood disaster management. The evolution of Indian remote sensing program over the past two decades, providing a variety of remote sensing- based solutions for national development, is an apt and timely national initiative. ISRO/DOS has launched a Disaster Management Support (DMS) Programme for integrating operationally the space technology inputs and services on a reliable and timely basis for strengthening India’s resolve towards disaster management. Towards enabling the operational services, a Decision Support Centre (DSC) is established at National Remote Sensing Centre, (NRSC), Hyderabad, as a single window provider, interfacing with the National / State disaster management agencies. The major components of the DSC include satellite/ aerial data acquisition, derivation of information in user required formats, output generation, dissemination of information to the users through the network, development of support functions such as digital database, query shells, hazard zonation, etc.

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METHODOLOGY Following are the major steps involved in preparation of flood inundation layer from the analysis of satellite data.

• Satellite data Planning and Acquisition: Satellite data from Indian Remote Sensing Satellites (IRS) and microwave satellite data from Radarsat satellites was acquired during the flood season of 1998-2010. The water levels observed at different gauge stations were closely monitored during floods and attempts were made to program the satellite data during peak/near peak situations. Satellite data was also programmed and procured during progression and recession of the flood wave for studying the impact of the flood.

• Rectification: The acquired satellite datasets were geo-rectified to Lambert Conformal Conic projection system with Modified Everest Datum for achieving positional accuracy.

• Flood inundation layer: Using image processing classification algorithms, water layer was extracted from the satellite data and integrated with the pre-flood river and water bodies layer to derive flood inundation layer. Fig 1 shows the methodology for extraction of flood inundation layer from satellite data.

• Annual Flood Layer: The flood inundation layers generated for different flood waves in a calendar year were integrated to generate the maximum flood inundation extent observed in that year.

Fig 1 Extraction of Flood Inundation layer from Satellite data

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DATASETS The Multi-date satellite datasets of 13 years(1998-2010) comprising of either IRS WiFS(188m) / IRS P6 AWiFS (56m) / Radarsat ScanSAR Wide / Narrow (100m & 50m) acquired during the flood season of that particular calendar year are used. SUGGESTED USE The flood maps can be used at broad level for the following purposes:

• Identification of frequently flooded areas. • Regulate land use in the flood plain areas. • Identification of Flood relief shelters

DISCLAIMER

• The satellite datasets acquired during the calendar years of 1998-2010 are available with DSC, NRSC.

• Most of the flood inundation layers were derived from microwave data since optical data was found to be cloudy during flood season. However, partially cloud-free datasets were considered for analysis.

• The satellite coverage may not correspond to the peak flooding in all cases. Further, all river gauge stations need not record the peak situation on a single day.

• For areas with gentle slopes, the flood inundation remains same for few days, even after the peak has passed. Hence, in most of the cases, satellite data acquired even after the flood peak resembles the peak situation.

• Observed flood inundation includes flooding due to embankment breaches and also due to rainwater accumulation in low lying areas.

USER RESTRICTION

I. Database could be used up to 1:250,000 scale. II. User of this data/information will consult NRSC to commercially exploit/use the

intellectual property generated in the Projects. CONTRIBUTORS S.NO NRSC-PROJECT MANAGEMENT PERSONNEL 1 DSC-Flood Team V Bhanumurthy, G Srinivasa Rao, P Manjusree,

C M Bhatt, SVSP Sharma, Asiya Begum, Sunil S Kulkarni, Vinod Kr. Sharma and S Mamatha

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CONTACT INFORMATION Deputy Director, RS &GIS Applications Area, National Remote Sensing Centre, ISRO, Department of Space, Balanagar, Hyderabad-500 625 Telephone: +91 40 2388 4211 Fax: +91 40 2387 5932 Email: ddapp@nrsc.gov.in CITATION Annual Flood Reports, DSC-Flood Project, Disaster Management Support Programme, RS&GIS AA, National Remote Sensing Centre, ISRO, Hyderabad ACKNOWLEDGEMENT Use of data in any form is to be duly acknowledged as shown below: I/We have used the flood inundation information for my/our research work from DSC-Flood Project, Disaster Management Support Programme, RS&GIS AA, National Remote Sensing Centre, ISRO, Hyderabad, India. REFERENCES

1. Manual on Flood Inundation Mapping - Service under Disaster Management Support Programme, Manual (July 2007) NRSC.

2. NRSC, (2011), Flood Hazard Atlas for Assam State- A Geospatial Approach, ISRO/DOS, Hyderabad http://ndem.nrsc.gov.in/hazard/