Mekong River Commission

8.1 Summary conclusions

Regionally, the flood season of 2006 saw below average conditions both in terms of flow volumes and peak discharges, most particularly on the lower mainstream downstream of Vientiane. To the north, however, flash flooding in Thailand and Lao PDR resulted in significant damage and loss. Deep monsoonal depressions that were largely confined to these northern provinces were generally responsible, though the wider regional impacts of Severe Tropical Storm Xangsane played a major role in early October, particularly in the south of Lao PDR. The major regional disaster in 2006 was the result of Tropical Storm Durian during December when extreme windspeeds and tidal surges caused immense damage in the Delta and southern coastal regions of Viet Nam.

 

8.2 Recommendations and lessons

The hydrological and water level data and information available for the mainstream are more than sufficient for a comprehensive assessment of the annual flood from year to year. Analyses of these historical data that have been reported here provide a framework for the objective and more perceptive evaluation of annual floods on the mainstream within their wider temporal and geographical context.

Tributary data analysis and information are far less complete at present, which amounts to a significant shortcoming, given the hazard of flash flooding in these river systems. The FMMP T2 Flood Risk Mapping Project on the Nam Mae Kok in northern Thailand is a recognition of this. Its modest extension to provide a regional flood risk analysis for the tributary systems upstream of Vientiane in both Thailand and Lao PDR would provide substantial ‘add on’ value. The HYCOS Project will also contribute much to the understanding of the flood hydrology of these tributary rivers.

In the longer term HYCOS will also add to the meteorological knowledge base and the nature of the linkages between regional storm rainfall and flood runoff. For the present purposes of the Annual Flood Report, however, daily satellite based rainfall estimates at the regional scale are sufficient and appropriate.

Finally, it is recommended that the Annual Flood Report be ‘theme’ based. Here the emphasis is on data analysis and the temporal and spatial nature of floods and flooding in the Mekong region. Such material provides an important supplement to the framework of knowledge within which the FMMP is being undertaken as well as contributing basic insight into the regime of the Mekong that are a necessary in many other contexts, for example the assessment of the environmental impacts of basin development. Other annual themes that should be considered are the socio-economic benefits and dis-benefits of the flood regime, meteorological aspects and the potential consequences of climate change, including links with ENSO. The report should also provide a medium for reporting FMMP progress in the interests of dissemination to the wider audience and stakeholders.