GEOMORPHOLOGICAL FEATURES AND SUBSURFACE GEOLOGY OF THE LOWER MEKONG PLAIN AROUND PHNOM PENH CITY, CAMBODIA (SOUTHEAST ASIA)

The geomorphological features of the Lower Mekong Plain and their relationships with floods, as well asthe subsurface geology and the major depositional processes in the area, are discussed. From theinterpretation of aerial photos and field reconnaissance, the Lower Mekong Plain in Cambodia ischaracterized as a floodplain with natural levees and back marshes. These geomorphological featuresinfluence the extent of the extensive inundation that occurs during every rainy (wet) season. An extremeflood in 2000 confirmed the close relationship between micro-landforms and the flooding. A preliminarystudy of bore-hole logs in the area of Phnom Penh was also carried out. Base rocks are shallower in thewestern part, whereas thick (>130 m) Quaternary deposits occur in the eastern part, suggesting the presenceof a structural basin.