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DAM SYNCHRONISATION AND FLOOD RELEASES IN THE ZAMBEZI RIVER BASIN: ANNEX 4 OF FINAL REPORT 6.5 Evaluation of the criteria of this study A B C D E F G H Criterion Technical and legal feasibility Contribution to flood protection Impact on Ecosystems Cost effectiveness Impact on human use Biophysical impact Likelihood of realization Impact on more than one country Flood risk zoning for rules for new settlements Flood risk zoning for current land use and awareness raising Figure 6.6: Assessment Flood Risk Zoning Flood risk zoning for insurances Flood risk zoning for rescue and warning Technical and legal feasibility The technical feasibility depends also on the data availability in the Zambezi region. Lack of data and frequencies of flooding limit the possibilities. The tables in Appendices explain the limitations. For flood risk assessment (and for flood forecasting) digital elevation data are important and the flood prone areas are generally the flattest areas in the basin. Remote Sensing techniques are improving and decreasing in cost, but for good digital elevation data considerable ground truthing is still necessary. Techniques for this (using GPS receivers) have also improved significantly in recent years. Vulnerability assessments can be improved with use of better data on population (number, poverty, livelihood), land use (annual cropping / multi-year cropping), infrastructure (condition of roads, culverts, bridges, water and sanitation, available refuge areas and clinics and hospitals, accessibility / possibilities to escape, communication options). For particular flood events those data have been collated, mainly for the Lower Zambezi. Population is the only statistic that is available in most countries, but censuses only take place once in ten years (last census in Namibia- 2001, Zambia -2000, Zimbabwe -2002, Malawi - 2008, Mozambique - 2007). Vulnerability capacity assessments have been done for about ten individual villages by the IFRC, which give an indication of livelihoods and further vulnerabilities. For insurance purposes with respect to the Zambezi River Basin, the problems that are being met by re-insurance companies in developing and developed countries (See Appendix E) show that the introduction of a flood insurance program for the Zambezi River at a basin-wide scale would be a major undertaking that lacks for the time being the essential elements such as a comprehensive set of flood hazard maps and preferably more advanced types of maps. The frequency of floods may also be too high for insurance purposes. Legally, flood insurance may be difficult for property on communally owned land. 62
DAM SYNCHRONISATION AND FLOOD RELEASES IN THE ZAMBEZI RIVER BASIN: ANNEX 4 OF FINAL REPORT Contribution to flood protection It needs to be assessed at a local level to what extent people are already aware of flood hazard potential whether they have and adjusted their settlement and land use activities accordingly or whether they are just accepting the risk. Only then, applied specifically for each area, does it make sense to invest in flood risk zoning to contribute to flood protection. From the rescue and warning side, the need for flood risk maps requires further investigation through disaster management centers. Their immediate need seems to be improved forecasting rather than flood risk zoning. A report on the flood of 2007 (Mozambican government et al., 2007) shows how organized rescue and warning procedures already are and the additional value of flood risk zoning should therefore be evaluated. Reports on the flood of 2007 (Mozambican Government, 2007) also indicate that people from areas outside flood risk zones seek to benefit from the services and assistance provided to people displaced by flooding. Mapping can contribute by benefiting only those that are really affected, although it still may be difficult to identify where displaced people come from. An investment could be done in coordinating different flood risk initiatives as illustrated in the Case Studies (Appendices F and G). The greatest value for the Zambezi region in coordinated flood risk mapping seems to be mostly in rescue and warning for international relief agencies to have similar information in the different countries. There is also value in coupling the mapping techniques used with a basin-wide flow forecasting model and additionally in informing downstream and upstream countries in ways that are familiar to these countries. Impact on ecosystems Preventing or decreasing human activity in the floodplain, based on flood risk zoning for new settlements and current land use, will be beneficial for the river ecosystem because anything that allows natural floods, and natural flooding of floodplains, to continue will enhance ecosystem functioning. There will be benefits not only to the aquatic fauna and flora, but also to the physical and chemical health of the system, as floodplains recharge groundwater, cleanse polluted water and store floods for slow release through the dry season. Offstream ecosystem benefits can also include improved floodplain grazing lands, flood-recession agriculture (if controlled wisely) fish stocks, and higher numbers of wildlife, all of which benefit from naturally functioning floodplains. The vulnerability of wildlife for floods, for the purpose of flood risk zoning, is difficult to evaluate. Chapter 5 in the recommendations for dam management explains that wildlife is on the one hand very dependent on flooding and on the other hand vulnerable, dependent on species and on circumstances. Rescue and warning for wildlife has been limited so far. In the extensive floods of 2001, almost 40% of the buffalos in the Zambezi Delta died, partly because most of the herd had withdrawn into a very wet area (to avoid landmines). Rescueing such herds seem to need real time knowledge of the location and not so much mapping flood risk zoning in advance. Impact on human use If flood risk zoning contributes to diminishing vulnerability of inhabitants, by timely warning or by modified settlements and land use, it will be beneficial. However, if flood risk zoning is stringently put in place it may prevent human activities which are necessary for livelihoods to survive in spite of the flood risk. Caution should therefore be made to assess the carrying 63
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