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Floods in Nepal

Friday, 29 August 2008

Type of Event:
Floods
Location of Event:
Nepal
Date of Charter Activation:
29/08/2008
Charter Requestor:
UNOSAT on behalf of UN-ESCAP; UN-OCHA
Project Management:
ESA

Description of the event

The Koshi River breached an embankment on 18 August, causing displacement of some 50,000 people and sweeping away seven villages in the Sunsari District. Deteriorating weather in the days following the break worsened the situation as flooding spread to the state of Bihar in India where media reported 46 dead on 27 August. According to the Red Cross, as many as 1.5 million people may be affected by the violent flooding of the Koshi.

Satellite-detected flood water over South Asia, covering the eastern Indian States of Bihar and Assam and the whole of Bangladesh. Areas with likely standing flood waters have been identified from Modis Aqua and Terra satellite imagery collected from 1 to 8 September 2008. The flood water extent from August 2007 is also presented for a time comparison. Pre-flood water levels were measured for 1-10 May 2007. Of special note is the distinct area of flood water along the old Kosi river channel in the Indian state of Bihar, the result of an embankment breach in southern Nepal on 18 August 2008. Estimates of flood water area (km2) have been calculated for the affected Indian and Bangladesh administrative units (levels 1 and 2) and are presented in tabular lists. Note: only units with flooded area values over 100km2 have been included. Preliminary analysis not yet validated in the field.

Source: MODIS Terra and Aqua, 250 m/pixel resolution.
Acquired: 1-8/09/2008; 1-10/05/2007, 2-22/08/2007

Copyright: Credit NASA 2007, 2008
Image processing, map created 12/09/2008 by UNOSAT.

Flood waters in Chhatapur Town, Supaul District, Bihar State, 24/08/2008

Source: ENVISAT-ASAR IMM and IRS L-4, 150 m/pixel (Envisat ASAR); 5.0 m/pixel (IRS L-4) resolution.
Acquired: 22/06/2008, 27/07/2008, 31/08/2008 (Envisat); 24/08/2008 (IRS L-4)
A total of 108 village/building cluster sites identified in this map extent, including the Taluk HQ town of Chhatapur are either totally or partially submerged by Koshi River flood waters as indentified with IRS satellite imagery on 24 August 2008. Additional flood analysis from ENVISAT-ASAR radar data recorded on 31 August and 5 September confirm that this area remains severely flooded.
Preliminary analysis not yet validated in the field.

Copyright: ESA 2008, ISRO 2008
Image processing, map created 05/09/2008 by UNOSAT.

Flood Waters in Sunsari and Saptari Districts, Nepal, 31/08/2008

Source: ENVISAT-ASAR IMM and ALOS Palsar, 150 m/pixel (Envisat ASAR) 12.5 m/pixel (ALOS Palsar) resolution.
Acquired: 22/06/2008, 27/07/2008, 31/08/2008 (Envisat); 24/08/2008 (ALOS)
Satellite-detected flood waters on 31 August 2008 for the affected Districts of Sunsari and Saptari, Nepal following a retaining wall breach on the Koshi River on 18 August 2008. Flood water detection was made using a time series of ENVISAT-ASAR (IMM) radar data recorded on 22 June, 27 July and 31 August 2008. The length of the retaining wall breach was estimated at 1,500 meters from ALOS-PALSAR radar data acquired on 24 August 2008. Preliminary analysis not yet validated in the field.

Copyright: ESA 2008, JAXA 2008
Image processing, map created 03/09/2008 by UNOSAT.

Flood waters in Bihar State, 31/08/2008

Source: ENVISAT-ASAR IMM, 150m/pixel resolution.
Acquired: 22/06/2008, 27/07/2008, 31/08/2008
Satellite detected flood waters for Bihar State following the embankment breach on the Koshi River in Nepal on 18 August 2008. Flood water detection was made using a time series of ENVISAT-ASAR (IMM) radar data recorded on 22 June, 27 July and 31 August 2008. Estimated flood water area has been estimated for admin level 3 units in km2. Preliminary analysis not yet verified in the field.

Copyright: ESA 2008
Image processing, map created 01/09/2008 by UNOSAT.