Figure 2. Correlation of linear progradation rates of the four delta systems.

Summary of the main intervals of delta growth of the Ebro, Rhone, Po and Danube systems, reporting their maximum rates as orders of magnitude (see Supplementary S1 and S3). Note that the time window is in two scales with 1 kyr steps, before 1500 AD, and 20 yr steps, onwards; delta growth rates are also summarized against a linear time scale in Figure 3. Two major and substantially synchronous phases of delta construction correspond to the expansion from 300 yr BC to 250 yr AD, and the last ca. four centuries, matching the Little Ice Age. Retreat of major delta fronts occurred after the Roman Empire and impacted almost all delta lobes during the last 50 yr (red bars).