The 2005 flood mainly affected two areas. The Northern region of Chiang Rai was affected by two flash flood
events and the section of the Mekong starting downstream of Nong Khai province and covering the provinces of
Nakhon Phanom and Mukdahan recorded high levels in the Mekong for a substantial period causing backwater
from the Mekong to flood the lower areas. This was combined with intensive rainfall which considerably reduced
the possibility of drainage from major tributaries to the Mekong. In addition, urban areas (mainly in Mukdahan)
were severely affected by heavy runoff caused by rainfall which was unable to drain into the Mekong.