Short-term relatively deep sedimentation on the Ebro delta coast. Opening the closure depth

摘要

Morphologial changes at the shoreface of the Ebro delta have been analysed with emphasis on the trabucador barrier, usign two types of approximations: (i) an aggregated-scale approach, i.e. by evaluating the depth of closure from comparison of beach profiles from a data set of 4years and, (ii) a process-oriented one, where changes are analysed in terms of driving factors and resulting sediment transport from a small scale experiment. Results frm the depth of closure analysis show that acting processes are restricted down to an average depth of 6.5m, with an important spatial variability. A year with high energy contents gives same results than using the whole data set. a sedimentation of about 7 cm was detected during the small scale experimetn at 8.5 m and 12.5 m depth under the passage of several storms. The analysed velocity field and sediment flux showed that onshore transport close to the bottom and offshore rtransport in the upper part prevailed under storms. These forcing conditions were similar to the registered in previous analysis although no morphological changes were previously detected. Results show that the depth of closure analysis is a good starter point to define morphological activity in the nearshore profile, but it has to be complemented with other type of approaches such us the process-oriented one to accurately define the limits for morphological activity.