Sentinel-1 Aids Response to Namibia Flood

©ESA

Namibian Floods

While Sentinel-1A is clearly demonstrating its versatility for monitoring many aspects of Earth, it has already been used for practical purposes. One of the satellite's first images was crucial in helping Namibian authorities decide how to respond to a serious flood.

In recent years, floods in Namibia have affected hundreds of thousands of people, destroying homes and washing away vital crops and livestock.

In this region, floods also bring further suffering in the form of disease, such as malaria and cholera.

Monitoring these devastating floods is normally hampered by the weather because sensors on aircraft cannot see through the cloud and are limited to relatively small areas. Trying to access remote flood-stricken areas on the ground is also impractical.

The country was subjected to another event this April, shortly after the Sentinel-1A launch.

Pauline Mufeti, Head of Namibia's National Hydrological Services, said, "Currently, it's practically impossible to monitor the situation from the ground because accessibility is difficult and virtually impossible during the rainy season.

"During this last flood, we could not determine where the water inundating villages was coming from. "The flooding in the Zambezi disrupts the livelihoods of the people and increases the risk of waterborne diseases."

Observations and tools offering immediate views over large areas are essential to prioritising and planning emergency response.

Satellites carrying radars, with the capability of imaging through clouds and during the dark, are essential for monitoring floods.

The National Hydrological Services use the Water Observation Information System, which was developed through ESA's Tiger initiative, to contribute to a daily Flood Bulletin for various national Namibian agencies.

Exploiting satellite data, this forecasting and monitoring capacity has been developed to map flooded areas in near-real time. Furthermore, the tool provides flood hazard assessments based on historical flood mapping.

The potential of the system was clearly demonstrated when the Zambezi River bust its banks a few weeks ago and flooded the border between Namibia, Zambia and Botswana.

Triggered by a flood alert from the Namibian Flood Bulletin, Sentinel-1A acquired one of its first images over the Caprivi flood plain on 13 April. The image was acquired in the satellite's main 'interferometric wide swath mode', which has a swath width of 250 km able to capture large floods such as this.

The data were downloaded and processed within less than three hours, showing how fast the mission can respond to such emergencies.

With the help of the Water Observation Information System, the scans were converted into a flood map, which helped the Namibian authorities to assess the situation and make decisions.

"Despite the bad weather and cloudy conditions we had been experiencing, Sentinel-1A could clearly depict the Zambezi flood plains from space," added Pauline Mufeti.

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