CHAPTER 7 I THE MEKONG DELTA IN THE FACE OF INCREASING CLIMATIC AND ANTHROPOGENIC PRESSURES I 345
2. Geological and hydrological characteristics of the Delta 2.1 Evolution and elevation of the Delta Deltas are geologically young landforms that have been formed during the past millennia. A delta is created when the volume of sediments accumulated over time at a location where a river enters a sea exceeds the volume (i.e. accommodation or accommodation space) that is created by sediment compaction and relative sea level rise. The surplus of both fluvial and marine sediments creates a delta extending into the sea. The elevation of this delta plain
is dynamic, and changes over time following sediment compaction and sea level fluctuations. When sea level rises, the elevation of a delta plain can be increased by deposition of new fluvial or marine sediments during floods, or by the production of organic sediments by vegetation on the delta plain. The Mekong Delta was formed over the last 6,000–7,000 years, when the sea level in southeast Asia reached a relatively stable level following its rise after the last ice age [ Hanebuth et al., 2012 ]. Under the influx of large quantities of primarily fluvial sediments brought in by the Mekong River, the Mekong Delta started to form its apex in present-day Cambodia [ Ta et al., 2005; Tamura et al., 2012 ]. Due to the combination of the relatively shallow seafloor underlying the present delta and the large sediment influx [ Anthony et al., 2015 ], the
[ Figure 7.3 ] Shoreline changes of the Mekong Delta between 2003 and 2012
Source: Anthony et al., 2015.
