Floods can occur in the Kunene River basin following heavy rains within the catchment, and serious flooding occurs when these coincide with heavy rain fall on the plateau in the Upper Kunene at the same time. A record wet season flow rate exceeding 1 750 m³/s was measured at Ruacana in March 2011, but peak flows are usually in the range 350 to 450 m³ per second.
Floods, when they happen, occur in the wet period of the year, from December to June, with rainfall peaking in the months of February and March. Serious flooding has occurred every year from 2007 to 2011.
In 2007 the floods came in January, following early heavy rains from the end of 2006 and right in the middle of a Cholera outbreak. In 2008 floods occurred in March and were relatively moderate.
The Kunene River basin has been hit by floods every year since 2007.
Source: IFRC/IPS 2009
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The floods of 2009, however, were dramatic, causing widespread destruction throughout the Kunene Province in Angola, where 125 000 people were directly affected and 25 000 people lost their homes, and along the northern parts of Namibia, where 276 000 were displaced. These floods resulted in the loss of crops, houses, schools, medical centres and road, and exacerbated a cholera outbreak in the Kunene Region in Namibia, and a direct rise in reported cases of Malaria. They were among the worst natural disasters to have hit the region in living memory. They struck again in March 2010, resulting in over 12 000 people affected by flooding.
Floods in the Upper Kunene sub-basin are generally local and of limited extent, due to the steep river gradient and well defined riverbed. In the Middle Kunene however, wide floodplains, known as the Kunene Flats, characterise the western bank of the river and flooding occurs in most wet seasons. Areas of up to 150 000 ha may be inundated, extending for nearly 150 km along the river, with maximum widths of 15 km. The depth of the river can increase from less than 1 m during low waters to 4.5 m during floods. The main tributaries, such as the Kaculuvar and Mucope rivers, add to the flood.
Flooding in northern Namibia in 2008.
Source: GTZ 2008
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Flooding in March 2011
In a previous geological era, the Kunene River basin was ‘endoeric’ (meaning that the main river outlet was not ending in the sea), and the main river flowed into the then permanent Etosha Lake. At some point in history, the main flow broke through to the west, where the Ruacana Falls are now, and then cut through to the sea. Gradually the main river incised itself in the landscape and the flows to Etosha disappeared, resulting in this becoming the ephemeral Etosha Pan, which very rarely contains water, only after very good rains and floods in the normally dry Cuvelai delta.
There has always been speculation as to whether heavy floods in the Kunene River would overflow the banks and contribute to the flows and floods in the channels of the Cuvelai delta, locally known as ‘iishana’. In early March 2011, a period of sustained heavy rains in the basin caused a flood wave exceeding 1 750 m³/s, seemingly the highest ever recorded. The satellite image below shows the area between Xangongo and Naulila where such overflow was considered possible but was not occurring. The image shows how the main channel incises against the high left bank (which is to the east on the image), with the typical depressions that are not connected with the Kunene River but drain to the 'iishana' of the Cuvelai in southwesterly direction. To the west of the channel are the floodplains and the low banks that gradually slope away from the river.
Source: Guido van Langenhove, personal communication 2011
Satellite imagery of Kunene River between Xangongo and Naulila.
Source: NASA Earth Observatory 2011, processed by Directorate of Resource Management, MWAF, Namibia, 2011
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Flooding in Kunene and Cuvelai Basin in March 2011.
Source: NASA Earth Observatory 2011
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