Namibia PDNA 2009 - GFDRR

of 2-6oC by end of the century, a later start and shorter rainy season in the northern regions, and possibly more intense extreme
events. The combined economic effects were estimated at 1.1 to 5.8 percent of GDP. Given the latest floods and droughts, there is a
need, however, to further assess future climate variability trends. This may include modelling indices such as rainfall intensity, wet day
sequencing, potential evapotranspiration, changes in water availability and average river flow. It also requires modelling the expected
changes in key hazards (floods, droughts and wildfires) brought about by climate change (see example of Figure 2). This modelling
may be carried out by global and regional centres of expertise, such as the University of Cape Town, the SADC Drought Monitoring
Centre in Botswana, and the Global Wildlife Monitoring Centre in Germany. It would be important to ensure that Namibian experts
are trained in the process.
Participatory Flood Risk Mapping
The final reconstruction decisions will depend largely on the level of safety deemed acceptable for the affected zones. Participatory
flood mapping can be a powerful tool for consensus decision-making and community consultation of reconstruction decisions in the
affected areas. The first step would be to simulate the disaster impacts of different flood return periods (e.g. once in 100 years, 1:
50, 1:25). The consensus should be to move to stricter safety levels if there is a chance of future loss of lives or extreme economic
hardship. The associated spatial delineation of areas “at risk” for the different return periods of flooding would then provide a basis for
participatory decision making. In general, the map would indicate the location of:
• Floodway: the normal river channel or high water area, prone to high velocities, high erosion and high levels of debris.
Apart from critical infrastructure such as bridges, no structures should be allowed in a floodway.
• Floodplain: the residual flooding area, where flood-protected structures could be allowed. However, all new
development should be compatible with a flood-prone area.
In some areas, a single-zone approach could be used. 16
Figure 38: Floodplain in Caprivi, April 2009
Map Source: MapAction
Once the initial safety-level mapping simulations were done, extensive stakeholder consultations would follow to reach a consensus
on the zoning regulations and flood-proof measures to be adopted. This would be particularly important if it involved the relocation
16 UN Department of Economic and Social Affairs, UNISDR and NOAA “Guidelines on Reducing Flood Losses.” ISDR. Geneva.
54
Namibia POST-DISASTER NEEDS ASSESSMENT