# Storm Adam: satellite map of candidate flooded areas around Oliva, Pego and Gandia
**Event:** Torrential rain and river flooding from Storm Adam, a cut-off low (DANA), 17–19 October 2026
**Where:** La Safor and Marina Alta, Valencia and Alicante, Spain
**Event date:** 17–19 October 2026
**Imagery compared:** three Sentinel-1 radar passes and one Sentinel-2 optical image, each against an image from before the event
**Facts checked:** 2026-11-14 · **Analysis packaged:** 2026-11-13T18:00:56Z
**Status:** Satellite-detected surface water: candidate flooded areas, not a confirmed flood extent. Impact figures are as reported; several are provisional.
## The story in brief
Storm Adam, a cut-off low (DANA) named by Spain's state meteorological agency AEMET on 16 October, brought torrential rain to eastern Spain from 17 to 19 October 2026. The comarcas of La Safor (Valencia) and Marina Alta (Alicante) were among the hardest hit. AEMET recorded 634 litres per square metre in 24 hours at Pego, spread across 18 and 19 October, and media reports gave about 713 mm at L'Atzúbia and about 600 mm at Oliva over the episode. The Girona and Vernisa rivers and the Beniopa ravine burst their banks. On 19 October RTVE reported four deaths linked to the storm: two in Oliva, one in Sagunto and one in Cabrera de Mar, near Barcelona. The same day Spain's civil protection authority asked the Copernicus Emergency Management Service for rapid flood mapping (activation EMSR935).
Comparing satellite images from before and after the event, we found **10 candidate flooded areas covering about 7.43 km²** of low, flat ground in the study area. These are places where surface water appeared that was not there before. They are candidates, not a confirmed flood extent: the satellites passed days after the peak, so some water had already drained, and some new water may have other causes, such as irrigation or ponds being filled.
## What has been reported
The figures below are as published by the sources shown. Where authorities had not confirmed a figure, it is marked as provisional.
- **Deaths:** 4: two in Oliva, one in Sagunto (Valencia) and one in Cabrera de Mar (Barcelona) — as reported on 19 October; some later reports give higher totals that we could not confirm, so they are not used here. Source: [RTVE](https://www.rtve.es/noticias/20261019/dana-adam-tiempo-espana-lunes-19/17272241.shtml), 19 October 2026.
- **Heaviest rainfall:** 634 l/m² in 24 hours at Pego (AEMET); about 713 mm at L'Atzúbia and about 600 mm at Oliva over the episode (media reports) — AEMET figure official; episode totals as reported. Source: [AEMET; Euronews](https://www.aemet.es/es/conocermas/recursos_en_linea/publicaciones_y_estudios/estudios/detalles/lluvias_torrenciales_oct2026), October 2026.
- **Rescues and evacuations:** 496 rescues and 2,141 evacuations by the Guardia Civil — as reported. Source: [The Watchers, citing the Guardia Civil](https://watchers.news/2026/10/20/four-deaths-reported-as-dana-adam-flooding-prompts-more-than-1-000-rescues-in-eastern-spain/), 20 October 2026.
- **Stay-at-home orders:** residents of 145 municipalities, about 800,000 people, were told to stay at home; the order was lifted on 19 October — official, as reported. Source: [RTVE](https://www.rtve.es/noticias/20261019/dana-adam-tiempo-espana-lunes-19/17272241.shtml), 19 October 2026.
- **Copernicus EMS mapping (EMSR935):** Moraira area: 897.7 ha flooded and 210.8 ha of flood traces on 20 October; Gandia area: 129.7 ha flooded and 915 residential buildings affected — rapid mapping from very-high-resolution satellite images of 20 October; not validated in the field. Source: [Copernicus Emergency Management Service](https://mapping.emergency.copernicus.eu/activations/EMSR935/), 20 October 2026.
## What the satellites show
- **Candidate flooded areas:** 10 areas (7.43 km²).
- 2 areas (6.69 km²) were detected by two or more independent observations, each covering at least a quarter of the area: the strongest evidence.
- 8 areas (74.1 ha) were detected by one observation, or by several that each covered only a small part of the area.
- **Land cover under candidate water** (ESA WorldCover 2021): cropland 4.56 km², herbaceous wetland 2.02 km², grassland 58.3 ha, tree cover 16.2 ha.
- **Main roads:** about 3.1 km of OpenStreetMap main roads lie within 20 m of candidate water. This shows exposure, not damage or closure.
- **Water already present before the event:** 2.11 km² on land (not counting the sea or permanent lakes and rivers), shown in navy on the map and excluded from the candidates.
### Observations
- **Sentinel-1, 22 Oct (descending)** compared with 16 Oct: 1.11 km² of new surface water detected; valid data over 54% of the study area.
- **Sentinel-1, 23 Oct (descending)** compared with 11 Oct: 2.42 km² of new surface water detected; valid data over 100% of the study area.
- **Sentinel-1, 23 Oct (ascending)** compared with 11 Oct: 2.54 km² of new surface water detected; valid data over 100% of the study area.
- **Sentinel-2, 21 Oct** compared with 8 Oct 2026: 7.51 km² of new surface water detected; valid data over 96% of the study area.
### Largest candidate areas
| ID | Area (ha) | Confidence | Main land cover | Nearest mapped town or village | Main roads within 20 m |
|---|---:|---|---|---|---|
| AD0001 | 493.9 | higher | cropland | — | AP-7 Autopista de la Mediterrània / Autopista del Mediterráneo, CV-678 carretera del Mar |
| AD0002 | 174.9 | higher | cropland | el Verger (3.8 km) | — |
| AD0003 | 51.4 | moderate | cropland | Xeraco (2.0 km) | — |
| AD0004 | 8.3 | moderate | grassland | el Verger (4.6 km) | — |
| AD0005 | 3.4 | moderate | herbaceous wetland | — | — |
| AD0006 | 3.2 | moderate | grassland | el Verger (4.4 km) | AP-7 Autopista de la Mediterrània / Autopista del Mediterráneo |
| AD0007 | 2.6 | moderate | herbaceous wetland | — | — |
| AD0008 | 2.1 | moderate | grassland | Xeraco (1.8 km) | — |
| AD0009 | 2.1 | moderate | herbaceous wetland | — | — |
| AD0010 | 1.0 | moderate | grassland | Oliva (4.2 km) | N-332 Carretera de Cartagena a Valencia |
### Main roads closest to candidate water
- AP-7 Autopista de la Mediterrània / Autopista del Mediterráneo: about 1.9 km within 20 m of candidate water
- CV-678 carretera del Mar: about 997 m within 20 m of candidate water
- N-332 Carretera de Cartagena a Valencia: about 208 m within 20 m of candidate water
## How this compares with Copernicus EMS
The Copernicus Emergency Management Service mapped flooding in part of this area from very-high-resolution images ([Copernicus EMS EMSR935, AOI01 Moraira delineation map (SPOT-6/7, 20 October 2026)](https://mapping.emergency.copernicus.eu/activations/EMSR935/)). Inside the part of its area of interest that it analysed:
- Copernicus EMS mapped **7.60 km² of flooded area** and 2.10 km² of flood traces (ground that had been under water).
- Our candidates cover **65%** of the Copernicus EMS flooded area. At least one of our observations flagged 66% of it before the minimum-size and confidence rules were applied.
- 73% of our candidate area there falls inside Copernicus EMS flooded areas or flood traces.
The two products differ in timing and resolution. Copernicus EMS used a 20 October 2026 image at about 1.5 m resolution; our radar passes came later, at 20 m, after some water had drained. Treat Copernicus EMS as the better reference wherever both exist.
## How we did it
1. **Radar (Sentinel-1).** Radar sees through cloud. Calm open water reflects the radar beam away from the satellite, so it looks dark. We compared terrain-corrected VV backscatter after the event with an image from before it, smoothing over 3 × 3 pixels of 20 m to reduce speckle. A pixel was flagged as new water when it was -18 dB or darker after the event, was brighter than that before, and had darkened by at least 3 dB.
2. **Optical (Sentinel-2).** Where the sky was clear, we compared the modified normalised difference water index (MNDWI, green against short-wave infrared). A pixel was flagged when the index rose from 0 or below before the event to 0.1 or above after it. Cloud and cloud shadow were removed using the scene classification layer.
3. **Where water can lie.** Only flat ground was assessed: slopes under 5° and land no more than 15 m above the lowest ground within about 2–4 km (Copernicus DEM GLO-30). Permanent water, and water already visible in the before images, were excluded. Built-up land was excluded from the radar test, because buildings scatter radar strongly and hide water.
4. **Confidence and clean-up.** Each observation counts separately. Flagged pixels were grouped into patches, and patches smaller than 1 ha were discarded. A patch is higher confidence when two or more observations each flagged at least a quarter of it, and moderate otherwise. Each patch was turned into a polygon and attributed with land cover, nearby main roads and the nearest mapped town or village.
## Limits
- **Candidates, not a confirmed flood extent.** Rain on ploughed fields, newly flooded rice paddies, filled fish or shrimp ponds and wet sand can all look like new water. Wind-roughened water can look bright to radar and be missed.
- **Timing.** The satellites passed days after the heaviest rain. Water that had already drained is not shown, so the true extent at the peak was probably larger.
- **Hidden water.** Flooding under tree cover or in built-up streets is largely invisible to this method.
- **Resolution.** Pixels are 20 m across, so narrow channels and small patches are missed. Areas are planimetric.
- **OpenStreetMap completeness.** Road and place data are incomplete in places, so proximity figures are minimums.
## References
1. Copernicus Emergency Management Service, “EMSR935: Flood in Alicante-Valencia Regions, Spain (activation page and products)”, 19–20 October 2026.
2. Copernicus Emergency Management Service, “Flood in Alicante-Valencia Regions, Spain (EMSR935)”, October 2026.
3. AEMET, “Lluvias torrenciales de octubre de 2026 (study of the DANA Adam episode)”, October 2026.
4. RTVE, “DANA Adam: live coverage, Monday 19 October”, 19 October 2026.
5. Euronews, “At least five killed and thousands evacuated as Storm Adam batters eastern Spain”, 20 October 2026.
6. The Watchers, “Four deaths reported as DANA Adam flooding prompts more than 1 000 rescues in eastern Spain”, 20 October 2026.
## Data sources and licences
- Copernicus Sentinel-1 radiometrically terrain-corrected backscatter (from GRD) — Copernicus Sentinel data terms (free, full and open); RTC processing by Microsoft Planetary Computer, CC BY 4.0. Attribution: “Contains modified Copernicus Sentinel data [2026]”.
- Copernicus Sentinel-2 Level-2A surface reflectance — Copernicus Sentinel data terms (free, full and open). Attribution: “Contains modified Copernicus Sentinel data [2026]”.
- Copernicus DEM GLO-30 — Copernicus DEM licence (free, worldwide, with attribution). Attribution: “Copernicus DEM GLO-30 © DLR e.V. 2010–2014 and © Airbus Defence and Space GmbH 2014–2018, provided under COPERNICUS by the European Union and ESA”.
- ESA WorldCover 10 m 2021 v200 — CC BY 4.0. Attribution: “© ESA WorldCover project 2021 / Contains modified Copernicus Sentinel data (2021) processed by ESA WorldCover consortium”.
- OpenStreetMap main roads, places and rivers (Overpass API) — Open Database Licence (ODbL) 1.0. Attribution: “© OpenStreetMap contributors, available under the Open Database Licence (ODbL)”.
- EOX Maps WMS (OpenStreetMap locator) — OpenStreetMap data under ODbL; rendering by EOX and MapServer. Attribution: “Locator: data © OpenStreetMap contributors (ODbL); rendering © EOX and MapServer”.
- Copernicus EMS EMSR935, AOI01 Moraira delineation map (SPOT-6/7, 20 October 2026) (used for comparison only; not redistributed) — Copernicus EMS products: free use with attribution. Attribution: “© European Union, 2026, Copernicus Emergency Management Service (EMSR935)”.
Contains modified Copernicus Sentinel data [2026]. OpenStreetMap data © OpenStreetMap contributors, available under the [Open Database Licence](https://opendatacommons.org/licenses/odbl/1-0/). The map and derived candidate polygons are released by TechnicalGIS under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). OpenStreetMap-derived attributes in the GeoJSON and CSV (road names, place names) remain under the ODbL. Copernicus EMS products were used for comparison only and are not included in this package.
Prepared by TechnicalGIS Environmental News Desk. Package revision 1.