dune slack Flat-bottomed, hollow zone within a sand-dune system that has developed over impervious strata. The slack may result from erosion or blow-out of the dune system, and the flat base level is therefore close to or at the permanent water-table level. Characteristically, dune slacks have rich, marshy flora, with Salix species (willows) as typical woody colonizers.

dune slack A flat-bottomed, hollow zone within a sand-dune system that has developed over impervious strata. The slack may result from erosion or blow-out of the dune system, and the flat base level is therefore close to or at the permanent water-table level. Characteristically, dune slacks have rich, marshy flora, with Salix species (willows) as typical woody colonizers.