Gloria Storm

Catalonia, Spain

DATES: 20-23 JANUARY 2020 | SATELLITE: SENTINEL 1 | CATEGORY: FLOODS

The storm named Gloria took place between the 20th and 23rd of January in 2020 on the Iberian Peninsula and in Northern Catalonia, with torrential rain along the Mediterranean coast and heavy snowfall in Aragón.

It caused great havoc and multiple incidents throughout the region and even took the lives of thirteen victims. This storm was the result of an easterly front, which meant it led to a great deal of precipitation. This caused an increase in the flow of the rivers, which added to the direct impact of the storm itself, thus affecting areas adjacent to riverbanks and all coastal communities.

To analyse this phenomenon through satellite images, we have used the data from the Sentinel-1 satellite from the Copernicus program. This satellite uses radar to capture data despite the prevailing weather conditions and even at night. Thanks to this radar, images could capture the very instant the storm occurred.

The effects on the Gloria storm on the Ebro Delta and the mouth of the Tordera River

The storm hit the Ebro River Delta especially hard, where waves reached over 14 metres high and seawater managed to penetrate up to three kilometres inland, occupying 3,000 hectares of rice fields.

In the Sentinel-1 satellite image, the blue tones denote bodies of water while the green and brown colours indicate areas not affected by the flood. Areas with rough waters are shown in light blue, while darker colours indicate the waters are calm. That is why there is a difference in colour between the two images.

Flood in the Ebro Delta during the storm Gloria on January 15th (left) and January 21st (right) 2020. Satellite image Sentinel 1. CC BY 4.0 Sentinel Hub EO Browser.

A comparison of these images shows the before and after of the Gloria storm and you can see how the Ebro Delta indeed was partially flooded. It is important to point out that during the storm the delta received water from the river, precipitation and the storm blowing in from the East. In this sense, you cannot tell the difference between saltwater and freshwater. As you can see in the image, it is impossible to distinguish between water coming from the sea and that which came from the overflowing Ebro River.

In the mouth of the Tordera River, 807 hectares were flooded, affecting the municipalities of Blanes, Tordera, Malgrat de Mar and Palafolls.

A large amount of debris consisting of organic material and plastics was flushed out by the Tordera River, ending up to the north of the Port of Arenys, precisely on Cavaió Beach, due to the coastal drift. Thousands of volunteers mobilised to clean up the remains of elephant grass, tree trunks and plastics that the waves washed up onshore.

The storm also affected the counties of Alt and Baix Empordà

Apart from the Ebro Delta, the storm caused other rivers to overflow their banks, such as the Ter. During the days that the storm lasted, various houses were evacuated and residents living on the lower section of the Ter River were trapped in their homes.

Flood in the Alt and Baix Empordà during the storm Gloria on January 17th (left) and January 22nd (right) 2020. Satellite image Sentinel 1. CC BY 4.0 Sentinel Hub EO Browser.

The radar images from the Sentinel-1 satellite also let us see the flooding of the flatlands in the county of Alt Empordà in the area of Roses. Here is the mouth of the Ter River in the county of Baix Empordà.

Other rivers were on the brink of overflowing, but never did, as was the case of the Onyar as it flows through the city of Girona.

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