Garcés Rafael, Roca Mar, Martínez-Clavel Borja, Blázquez Ana M
Environmental and Marine Sciences Research Institute (IMEDMAR-UCV), Catholic University of Valencia, C/ Guillem de Castro 94, 46003 Valencia, Spain.
Institute of Marine Sciences of Andalusia (ICMAN), Spanish National Research Council (CSIC), Cádiz, Spain.
Sci Total Environ. 2023 Dec 20;905:167296. doi: 10.1016/j.scitotenv.2023.167296. Epub 2023 Sep 22.
Deltas and estuaries are formed through periods of marine transgression and regression, which are the continuity of a river and provide key information about its evolution. However, many of the world's deltas are increasingly exposed to the impacts of human activities. While changes affecting the subaerial parts of deltas have been intensively studied, much less is known of their subaqueous parts, the understanding of which is important in gauging overall potential delta vulnerability. This research evaluates the bathymetric changes in the submerged delta of the Turia river (Western Mediterranean, Spain) before and after the extreme flood event of 1957, after which the riverbed was diverted. Three nautical charts were processed (1878, 1988 and 2022), including georeferencing and Digital Elevation Model (DEM) generation. In order to evaluate changes before and after the event, models for 1878-1988 and 1988-2022 were compared and differences were quantified in order to assess erosion and aggradation trends. The results indicate a more aggradated submerged delta in the surroundings of the old river mouth, favored by the high sediment availability since the end of the Little Ice Age (LIA), and the presence of a smaller delta next to its current river mouth to the south of the harbor of Valencia. Bathymetric reconstructions also made it possible to map some incisions in the inner continental shelf as river channels that migrated eastwards when the sea level was lower during MIS 2. Finally, the comparison of bathymetric models also revealed the scarcity of sediments on the current shelf since 1988, which is attributed to anthropogenic action. The successive extensions of the harbor are increasingly distorting the distribution of sediments along the coast and are thus remodeling seabed sediment distribution. Knowing the sedimentation in deltaic systems means better predicting future alterations due to increased anthropization and of the climate change.
三角洲和河口是在海侵和海退时期形成的，它们是河流的延续，并提供了有关其演变的关键信息。然而，世界上许多三角洲越来越受到人类活动的影响。虽然影响三角洲陆地上部分的变化已得到深入研究，但对其水下部分的了解却少得多，而了解水下部分对于评估三角洲整体潜在脆弱性很重要。本研究评估了图里亚河（西班牙西部地中海）淹没三角洲在1957年极端洪水事件前后的水深变化，该事件之后河床被改道。处理了三张海图（1878年、1988年和2022年），包括地理配准和数字高程模型（DEM）生成。为了评估事件前后的变化，比较了1878 - 1988年和1988 - 2022年的模型，并对差异进行了量化，以评估侵蚀和淤积趋势。结果表明，在旧河口周围，淹没三角洲淤积更明显，这得益于小冰期（LIA）结束以来的高沉积物供应量，以及在巴伦西亚港以南其当前河口旁边存在一个较小的三角洲。水深重建还使得能够绘制内陆架上的一些下切河道，这些河道在末次冰期第2阶段海平面较低时向东迁移。最后，水深模型的比较还揭示了自1988年以来当前陆架上沉积物的稀缺，这归因于人为活动。港口的连续扩建越来越扭曲了沿海沉积物的分布，从而正在重塑海床沉积物分布。了解三角洲系统中的沉积情况意味着能够更好地预测由于人类活动增加和气候变化导致的未来变化。
