Signatures of sea level changes on tidal geomorphology: experiments on network incision and retreat.

How do tidal networks respond to changes in relative mean sea level (RMSL)? The question on whether the morphological features of a tidal landscape retain signatures of past environmental forcings, or are in equilibrium with current ones, is critical to our prediction of the fate of residual tidal landforms. In the case of tidal networks, the issue is quite relevant owing to their fundamental role on landscape eco-morphodynamic evolution. Here we explore the response of tidal networks to cyclic variations in RMSL triggering tidal prism changes on the basis of laboratory experiments carried out in a synthetic lagoonal environment. A decrease in the tidal prism leads to network retreat and contraction of channel cross sections. Conversely, an increase in the tidal prism promotes network re-incision and re-expansion of channel cross sections: Network retreat and expansion tend to occur within the same planar blueprint. Our results show that the drainage density of tidal channels is linearly related to the landscape-forming prism, although this relation is speculated to hold with reasonable approximation as a statistical tendency rather than as a pointwise, instantaneous adaptation. Changes in tidal prism rapidly influence network efficiency in draining the intertidal platform and the related transport of water, sediments, nutrients and pollutants. This bears important consequences for quantitative predictions of the long-term ecomorphological adaptation of the