Comparative spit dynamics. The case of deltaic river mouth spits

Zăinescu, I.F.; Vespremeanu-Stroe, A. and Tătui, F., 2016. Comparative spit dynamics. The case of deltaic river mouth spits. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 800–804. Coconut Creek (Florida), ISSN 0749-0208. This paper presents a comparison of evolution and dynamics of selected representative deltaic spits. Although recently receiving more attention, deltaic barrier spits still remain poorly understood in terms of long term evolution. Water, sediment and wave interactions at the river mouth are highly nonlinear such that hydrodynamic groin effects and sediment trapping mechanisms generate behaviours such as cyclic lobe progradation, as it is the case of some deltaic lobes, or conversely impose river mouth deflection when the wave influence becomes dominant. River mouth spits can be part of a prograding lobe (e.g. Sacalin and the paleo-spits of the Danube Delta lobes, Ba Lat spits) or can be a sign of lobe abandonment due to lobe switching, geoengineering or extreme reduction in sediment supply (e.g. La Banya, Ebro; Gracieuse, Rhone; Damietta, Nile). Human-induced reductions in river solid discharge have affected the majority of Mediterranean deltas and there is a wealth of other examples worldwide (e.g. Krishna & Godawari deltas). Dependent on the wave climate and especially the wave direction, cuspate features, migrating sand waves or flying spits form at the downdrift side of lobes. Comparison of dynamics shows that spits experience high temporal (inter-decadal), spatial (alongshore) and inter-landform variability. Dynamics is complex, often resulting from different interrelating effects which importance in control can change over time.