Impacts of extreme rainfalls in the year 2006 to the vegetation cover on different geomorphological units of the central Kaukausib catchment, southern Namib Desert (Namibia)
The dynamic and tempo-spatial development of land cover changes focussing on vegetation development as a result of extraordinary rainfalls in the hyper-arid southern Namib Desert in 2006 is analysed through the use of mid-scale remote sensing satellite imagery (Landsat 5) and the derivation of two vegetation indexes (NDVI & MSAVI2). Interpretation is supported by the analysis of morphometric parameters of the landscape derived from a Digital Elevation Model (Aster GDEM v2). Archived climate weather maps provide meteorological information of the synoptic situation of the atmosphere, forcing strong rainfalls in the southern Namib Desert between April 16 to 22, 2006. The results show, that rainfall was triggered by an Cut-off-Low from the temperate climate system of southern Africa reaching unusually far north and a Temperate Tropical Trough reaching unusually far south at the same time. Vegetation density vitality has its maximum three months after the strong rainfall, where in some regions of the study area a rather dense cover of annual and ephemeral grass occurred. In addition to intense changes in vegetation cover, the Anib and Arasab pans as part of the Kaukausib catchment were flooded for several months. The tripartite approach integrating meteorological, morphometric and biological aspects allows us to use this case study as one of the very rare opportunities to study regional scale vegetation changes in a hyper-arid area by the use of remote sensing techniques.
Evidences for a recurrence of this phenomenon during the last 30 years in this region based on the study of archived data show that they have an interval between 5-11 years. Although the region gets mean annual average precipitation of less than 50 mm, it shows that these strong rainfalls are a common feature and might have a high significance for the regional and over-regional ecosystems. The understanding of this is very important, as the southwestern part of Namibia marks the critical boundary zone of sub-tropical to temperate frontal zones and is therefore a highly sensitive region with regard to climate changes and past circulation patterns, but also to predict future situations.
Henselowsky, Felix,Pflueger, Ole,Bubenzer, Olaf. Impacts of extreme rainfalls in the year 2006 to the vegetation cover on different geomorphological units of the central Kaukausib catchment, southern Namib Desert (Namibia)[J]. ZEITSCHRIFT FUR GEOMORPHOLOGIE,2019-01-01,62:161-181