The maximum flow of the Poyo in Torrent was equivalent to two Olympic pools per second in the dana and the narrowing downstream overflowed it, according to ICBiBE

Thus, the Poyo in Torrent recorded 5678 m3 per second (one m3/sec is equivalent to 1000 litres in a section of one metre by one metre, in one second); the maximum of the Magro in Carlet was 4198 m3/sec; and the Turia in Pedralba recorded a peak of 2596 m3/s.

"The average flow rate of the Poyo Creek by Torrent is equivalent to the water that would fill two Olympic pools every second (50 by 25 meters with almost three depth); or the water that could carry 300 tank trucks filled every second", explains Juan M. Soria, researcher at the Cavanilles Institute of Biodiversity and Evolutionary Biology (ICBiBE), located in the academic scientific area of the University of Valencia Science Park (PCUV), which has led this research published in the journal Water. The Ministry of Science, Innovation and Universities has recently awarded the scientific contribution of Juan Soria to the reconstruction after Dana.

The study identifies "bottlenecks" in the water drainage network. These critical points occur where the downstream section of a channel is significantly smaller than the upstream section. In the rambla of Poyo, the confluence with the ravine of the Horteta in Torrent threw a cross-section wet of 2271 m 2. However, the section is restricted progressively downstream, being reduced by a distance of 10 km to 205 m2 near Massanassa. This traffic jam was the cause of widespread flooding between Torrent and Massanassa, which resulted in material damage and numerous victims, details Rafael Muñoz, ICBiBE researcher and first signatory of the article.

"In the Rambla of Poyo, the confluence with the ravine of the Horteta in Torrent threw a cross-section wet of 2271 m 2. However, the section is restricted progressively downstream, being reduced by a distance of 10 km to 205 m2 near Massanassa. This traffic jam was the cause of widespread flooding between Torrent and Massanassa, which resulted in material damage and numerous victims", Rafael Muñoz, ICBiBE researcher and first signatory of the article

A prominent example is also the Magro river, where a drastic reduction in wet cross-section was observed: it went from 1679 m2 in Carlet to only 243 m2 in Algemesí. This reduction explains the massive overflow, estimated at 3590 m 3/sec, which flooded Algemesí and its surrounding areas. The validity of this empirical measurement procedure was rigorously tested by the Manning equation, which is widely used in hydrological calculation from variables such as slope, stream type and water section

From an ecological perspective, the impact on the Albufera of Valencia was severe, with a 82% drop in water conductivity below pre-DANA values. In addition, a substantial layer of sediment has been deposited at the bottom of the lagoon, a phenomenon that was already highlighted by preliminary sedimentation studies.

"The study highlights the urgent need to use these data obtained to update territorial planning tools, such as PATRICOVA, and implement structural interventions to improve the capacity of the channels.", Noelia Campillo, ICBiBE researcher and participant in this research

 "The study highlights the urgent need to use these data obtained to update territorial planning tools, such as PATRICOVA, and implement structural interventions to improve the capacity of the channels," says Noelia Campillo, ICBiBE researcher and participant in this research.

The 2024 event was the most important in the Poyo basin in the last 80 years, the second in the Turia and the third in the Júcar, according to the records consulted. The probability of a similar flood is 8.8% for the Júcar basin and 2.5% for the Turia and Poyo basins, says Juan Víctor Molner, who also signed the scientific article.

Section of the Rambla of Poyo in Torrent and map of the peak flows, in m3/s at various points of the rivers Turia and Magro and of the ravines that drain the Albufera of Valencia. Photo: UV News

Methodology

The researchers used an empiricalEvent to estimate peak flows at specific points in basins due to the sporadic and unpredictable nature of these phenomena and limitations of real-time data collection systems during extreme events such as the System Automatic Hydrological Information of the Júcar Hydrographic Confederation  (SAIH).

The approach was based on the analysis of physical evidence left by the highest level of flooding, using wet cross-sectional calculation at 25 key sampling points. Using the existing official flow data network, the average water velocity was estimated. The results provided estimates of peak flow rates at several sites, which greatly exceeded the transport capacity of the channels, resulting in major flooding and overflows.