Mekong River in Cambodia
Obstacles to navigation from Stung Treng to Sambor
Further downstream in Stung Treng, the river is wide and navigable but requires a lot of skills from the pilot/captain in passing the rapids and often the narrow gaps are not more than 70.0 m (Km 660.5) in a 2,350 m wide waterway (monsoon river bed). The river is obstructed with scattered rocks and islands, most of them with vegetation (bushes) bended from being pushed during long months of flooding. A great number of parallel-aligned reefs (directed North-South) are crossing the channel and hindering navigation.
However, the navigation channel remains deep (20.0 to 40.0 m) but obstructions from reefs and rock outcrops, sometimes across the waterway, makes navigation without the French markers a difficult undertaking.
At some places there are two channels, both marked by French markers. One of the channels is usually very narrow but both are deep enough. However, this situation only occurs during low water.
Source: Design of a Master Plan for Regional Waterborne Transport in the Mekong River Basin, Volume I, Page 34, 35