Attachments
1. Introduction
As in 2006, the 2007 Annual Flood Report aims to fill two primary roles, (i) to provide a summary of flood conditions in the Mekong Region over the year, and (ii) to collate the relevant data and information. The Report also has an annual ‘theme’. Having contributed significantly to the understanding of Mekong mainstream floods and flooding in the 2006 Report, this document has made the logical progression and taken the flood hydrology of the tributaries as its theme, with flash floods meriting particular attention.
2. The flood hydrology of the major tributaries in the Lower Mekong Basin
2.1. An introductory note on the impacts of land-use change and deforestation on the flood regime of the Mekong tributary rivers
The belief that deforestation causes an increase in the frequency and severity of major floods and compounds the damage that they do appears to be widespread. This view is as widely held within the Mekong Basin as it is throughout the tropical world. However, an authoritative Report from the UN’s Food and Agriculture Organization (FAO) and the Centre for International Forestry Research (Cifor) says that the evidence shows no link. That flood damage is increasing is unquestioned; however this is not linked to the increasing magnitude of events but is due to the growing global population and the consequent expansion of human settlements into areas which had once been marginal. As a result, each flood claims more lives than it would have done a century ago. In addition the human diversion of watercourses and the construction of flood protection works often moves the problem from upstream to downstream areas.
There are arguments and some evidence to suggest that the actual frequency of floods is beginning to increase, possibly in response to climate change, a major consequence of which, it is generally agreed, will be an increase in the incidence of extreme events.