Aeolian dynamics of transgressive dunefields on the southern Mozambique coast, Africa

Abstract

A relatively unknown coastal zone of southern Mozambique in Africa is covered by vast mobile and stabilized dunefields. The aeolian dynamics of these transgressive dunefields are studied based on mobility and stability models, statistical analysis of climate data and topographic profiles. Detailed analyses of regional winds, rainfall records, atmospheric temperature records and annual monitoring of dune migration rates helped to find reliable data about instantaneous aeolian sand transport rates, wind drift potential, dune mobility and dune migration rates. The data obtained suggest that the coastal transgressive dunefields are controlled by the southeast winds, availability of loose sediments on the beach, the presence of headland boundary between Maputo and Gaza provinces and the appropriate deposition spaces between the coastline and lacustrine‐lagoon systems. Two distinctive segments of transgressive dunefields were identified in the region studied, including the northern segment of Maputo province with active (mobile) and semi‐vegetated dunes that migrate 23 m/yr landward, and Gaza province dunefields with stabilized (vegetated) and semi‐vegetated dunes. The data obtained in this research have considerable potential to make a valuable contribution to the study of coastal dunefields. Copyright © 2018 John Wiley & Sons, Ltd.

The morphodynamics of transverse dunes on the coast of South Africa

“…This relationship is not observed at Kaysers Beach or Rockclyffe-on-Sea where there are no significant incoming rivers, but the role of other site-scale factors cannot be excluded for other beach-dune systems (e.g. Miguel and Castro, 2018).…”

“…As such, transverse dunes can be clearly distinguished from foredunes that are broadly aligned parallel to the shoreline and that are located at the back of the beach. Many studies have examined the nature of windflow over transverse dunes, from in situ field measurements and numerical modelling (van Dijk et al, 1999;Reffet et al, 2010;Melo et al, 2012;Araújo et al, 2013;Jiang et al, 2014;Jackson et al, 2020), but there are fewer studies of the morphometry and morphodynamics of transverse dunes (Hunter et al, 1983;Miguel and Castro, 2018;Knight and Burningham, 2019). This includes calculations of dune migration rates, based on field or remote sensing data, which can be linked to the development of the dune bedform with respect to wind forcing (Tsoar and Blumberg, 2002;Miguel and Castro, 2018;Knight and Burningham, 2019).…”

Late Holocene evolution of a coastal barrier system at Bilene, Mozambique

“…The dune migration observed in the study area is oriented from the southeast to the northwest facilitating the transport of aeolian sediments towards the hinterland, often promoting the silting or filling of the lacustrine-lagoon systems (Miguel & Castro, 2018). The monthly wind speed average, mostly influenced by the monsoon system in the North, and the SE and SW trade winds in the central and southern coasts, may reach 11 m/s with predominant frequencies from the NE, E, SE, S and SW (Miguel et al, 2019).…”

“…It is almost parallel to the coastline, which shelters back-barrier lakes and lagoons from a sea connection, forming a barrier-lagoon system. It is believed that the local Limpopo River (located northward of Bilene Barrier-Lagoonal System) and Incomati River (located southward of Bilene Barrier-Lagoonal System) are responsible for the high sediment supply to Bilene, also benefiting from large quantities of unconsolidated aeolian sands in the littoral zone (Miguel & Castro, 2018). The association of sand supply, mobile dune fields and the SE blowouts and somewhat from the SW have been responsible for building-up one of the largest transgressive dune fields of Africa with about $150-m height above the present-day mean sea-level.…”

“…In addition, wind regimes acting in Mozambican coast are mostly influenced by the monsoon system from the North, and the SE, and the SW trade winds in the central and southern coasts (Miguel & Castro, 2018). Its persistent action associated with the conditions in the south intertropical region favours the occurrence of progradation process of barrier systems along the coast of Mozambique (Miguel & Castro, 2018). The persistent action of wave climate, favoured by the mesotidal regime and winds predominantly from the southeast and those from the southern quadrants with speeds above 6.0 ms À1 (Miguel et al, 2019), favours the development of sandy coastal ridges, barrier islands, barrier-lagoon systems, transgressive dune fields and extensive beaches.…”