Presentation Information
[T7-P-14]Field investigation of crevasse splay deposits associated with the 2024 Spain flood
*Masaki YAMADA1, Gen SASAMOTO1, Amy DRAEGER2, Hachem KASSEM2, Patricio Guillermo VILLAFAÑE3, Micaela DELLA VEDOVA4, Roland GARNIER5, Masashi WATANABE2 (1. Shinshu University, 2. University of Southampton, 3. Universitat de València, 4. CONICET–UNT, 5. AZTI)
Keywords:
River flood,Flood deposit,Crevasse splay deposit,Valencia
The flood that occurred in Spain on October 29, 2024, was one of the most devastating disasters observed in Europe in recent years, causing extensive damage over a wide area. More than 200 people lost their lives in southeastern Spain, including in major cities such as Valencia and Málaga, and tens of thousands of households were inundated. The flood also had severe impacts on agriculture and transportation infrastructure.
Field investigations of large-scale modern floods are crucial for understanding the magnitude of such events and the processes of river flooding. In Spain, the regional government of Valencia (Generalitat Valenciana) has published geographic data on flood extent and water depth related to the DANA (Depresión Aislada en Niveles Altos) event of October 29, 2024. These data provide valuable insights into the broad-scale flood dynamics, but they are insufficient for reconstructing localized overbank flows and sedimentary processes in detail.
Against this backdrop, we conducted a field survey from July 1 to 7, 2025, in a paddy field area on the right bank of the Túria River near Catarroja, Valencia. The site was selected based on interpretation of aerial photographs taken immediately after the event, which revealed large-scale crevasse splay morphology. According to the published geographic information from the regional government, the maximum inundation depth in the study area was approximately 1 meter. As nine months had passed since the flood, most flood-derived deposits had already been removed due to recovery efforts. However, through cooperation with local construction workers, a portion of the flood deposits, including the crevasse splay deposits, was left in place using heavy machinery, allowing us to investigate a 43-meter-long continuous sedimentary exposure oriented perpendicular to the river.
The exposed section was cleaned using hand tools (sickle with curved blade), followed by sedimentary description and thickness measurement at 1-meter intervals. A 3D record of the outcrop was also created using LiDAR scanning and photogrammetry with an iPhone 15 Pro Max and the Polycam app. In addition, sediment samples were collected at 5-meter intervals from the basal, middle, and upper parts of the crevasse splay deposit for grain size analysis.
The crevasse splay deposit was light brown in color and composed mainly of fine sand. The underlying paddy soil was dark in color, and the presence of charred rice stalk bases remaining on its surface after post-harvest burning allowed for easy identification of the stratigraphic boundary. The boundary was sharp and erosive, indicating typical characteristics of an event deposit. The deposit thickness varied substantially along the 43 m outcrop (ranging from 20 to 65 cm), despite the absence of significant topographic relief at the site. The crevasse splay deposit can tentatively be divided into three sedimentary facies: (1) a lower mud-rich sand layer showing climbing ripple lamination, (2) a middle sand layer with parallel lamination, and (3) an upper sand layer with cross lamination. As this abstract was prepared immediately after the fieldwork, detailed analytical results are not yet available. However, we plan to conduct further analyses of grain size distributions and sedimentary structures by the time of the conference, with the aim of discussing the formation processes of the crevasse splay deposit and the breach dynamics of the levee.
Field investigations of large-scale modern floods are crucial for understanding the magnitude of such events and the processes of river flooding. In Spain, the regional government of Valencia (Generalitat Valenciana) has published geographic data on flood extent and water depth related to the DANA (Depresión Aislada en Niveles Altos) event of October 29, 2024. These data provide valuable insights into the broad-scale flood dynamics, but they are insufficient for reconstructing localized overbank flows and sedimentary processes in detail.
Against this backdrop, we conducted a field survey from July 1 to 7, 2025, in a paddy field area on the right bank of the Túria River near Catarroja, Valencia. The site was selected based on interpretation of aerial photographs taken immediately after the event, which revealed large-scale crevasse splay morphology. According to the published geographic information from the regional government, the maximum inundation depth in the study area was approximately 1 meter. As nine months had passed since the flood, most flood-derived deposits had already been removed due to recovery efforts. However, through cooperation with local construction workers, a portion of the flood deposits, including the crevasse splay deposits, was left in place using heavy machinery, allowing us to investigate a 43-meter-long continuous sedimentary exposure oriented perpendicular to the river.
The exposed section was cleaned using hand tools (sickle with curved blade), followed by sedimentary description and thickness measurement at 1-meter intervals. A 3D record of the outcrop was also created using LiDAR scanning and photogrammetry with an iPhone 15 Pro Max and the Polycam app. In addition, sediment samples were collected at 5-meter intervals from the basal, middle, and upper parts of the crevasse splay deposit for grain size analysis.
The crevasse splay deposit was light brown in color and composed mainly of fine sand. The underlying paddy soil was dark in color, and the presence of charred rice stalk bases remaining on its surface after post-harvest burning allowed for easy identification of the stratigraphic boundary. The boundary was sharp and erosive, indicating typical characteristics of an event deposit. The deposit thickness varied substantially along the 43 m outcrop (ranging from 20 to 65 cm), despite the absence of significant topographic relief at the site. The crevasse splay deposit can tentatively be divided into three sedimentary facies: (1) a lower mud-rich sand layer showing climbing ripple lamination, (2) a middle sand layer with parallel lamination, and (3) an upper sand layer with cross lamination. As this abstract was prepared immediately after the fieldwork, detailed analytical results are not yet available. However, we plan to conduct further analyses of grain size distributions and sedimentary structures by the time of the conference, with the aim of discussing the formation processes of the crevasse splay deposit and the breach dynamics of the levee.