Model for a dune field with an exposed water table
GEOMORPHOLOGY, (2012)DOI: 10.1016/j.geomorph.2012.03.021
Abstract
Aeolian transport in coastal areas can be significantly affected by the
presence of an exposed water table. In some dune fields, such as in
Lencois Maranhenses, northeastern Brazil, the water table oscillates in
response to seasonal changes of rainfall and rates of
evapotranspiration, rising above the ground during the wet season and
sinking below in the dry period. Understanding dune mobility in an
environment with a varying groundwater level is essential for the study
of long-term evolution of many dune fields. Here we apply a model for
aeolian dunes to study the genesis of coastal dune fields in the
presence of an oscillating water table. We find that the morphology of
the field depends on the time cycle, T-w, of the water table and the
maximum height, H-w, of its oscillation. Our calculations show that long
chains of barchanoids alternating with interdune ponds, such as those
found at Lencois Maranhenses, arise when T-w is of the order of the dune
turnover time, whereas H-w dictates the growth rate of dune height with
distance downwind. (c) 2012 Elsevier B.V. All rights reserved.