Tidal depressions in coastal wetlands: a new look to an old geomorphologic feature.

PERILLO, G.M.E.

Shanghai

Congreso; ECSA 2017 Where land meets ocean: the vulnerable interface; 2017

East China Normal University

Tidal depressions, otherwise known as ponds, pans, pools, etc., are any surface concavity in a wetland either originated by tidal processes or another origin, which evolution depends on the geomorphologic and biologic characteristics and tidal-influenced dynamic processes acting on the wetland (Perillo, in press). Even though the earlier researchers have recognized their importance as both geomorphological and biological features, the interest in their study has decayed significantly in the last century to come out again in the open within the last decades, but still maintaining a low profile.We introduce a new classification of tidal depressions based on size range (only depth (d) and area (A) since shape is very variable) in : a) Tidal pans: intermittently inundated depressions, d ≤ 5 cm, A ≤ 2 m2; b) Tidal ponds: permanently inundated depressions, d ≤ 50 cm, 2 m2 < A < 20 m2; c) Tidal pools: large depressions d > 50 cm, A≥ 20 m2; d) Tidal scour holes: deep depressions at the intersection of tidal courses.In the present context, we also analyze different mechanisms of tidal depression formation and evolution, and their relationship with tidal courses as well. New techniques based on unsupervised segmentation and shape extraction from satellite and aerial images are presented that provide statistical approaches to understand their complex distribution and patterns, especially in tidal flats, where depressions have been highly neglected.