Riverbank changes along the Mekong River: Remote sensing detection in the Vientiane–Nong Khai area

Riverbank erosion is a natural process, but often human activities can have a significant impact on the rates of morphological change. This paper aims to assess bank erosion problems in the Vientiane–Nong Khai section of the Mekong River, where the Mekong borders Thailand and Lao PDR. The study provides new and more accurate information about recent riverbank movement rates. The bank movement rates are quantified using two Hydrographic Atlases dated 1961 and 1992, derived originally from aerial photos and a field survey, and SPOT5 satellite images acquired on 4 December 2004 and 28 April 2005 with a resolution of 2.5 m in natural colours. Bank erosion and accretion rates on the left (Lao PDR) and right (Thailand) banks of the Mekong are analysed for two time periods: 1961–1992 and 1992–2005, respectively. The quantified average bank erosion rates were found to be slow, ranging from 0.8 to 1.0 m/a for the first and second analysis period, respectively. These average annual erosion rates are only 0.1% of the channel width, which is very low on a global scale. However, erosion rates were much higher for the islands in the river, 2.4 and 4.8 m/a for the two time periods. The quantified accretion for the main banks was 0.4 m/a during 1961–1992 and 0.7 m/a during 1992–2005, which for the islands increased from 0.6 to 6.4 m/a from the first to the second period.