Field Trip to Nam Chung
Info-sheet
Checkpoint 6: Ping Nam Cascade
Characteristics of the upper course of the river
The characteristics of the river change a great deal from what we saw at
checkpoint 1. The gradient becomes very steep. The river channel is narrow forming
a deep V-shaped valley. This is mainly because vertical erosion is dominant here,
undercutting mainly the river bed and resulting in the formation of a narrow and deep
valley. The river course is straighter and the size of sediments is much larger than
those in the lower course. These sediments may be those fallen down from nearby
slope due to denudation or those eroded by the river. Since the distance of travel is
short, less erosional processes are acting on them. So they remain large in size. All
these are characteristics of the upper course of a river.
The photos and video clips also show another typical feature in the upper
course – a series of waterfalls which we called a cascade. It is formed when vertical
erosion of a river undercut the river bed making up of rocks layers of different
resistance.
The water cycle in Nam Chung
The following diagram shows how the water cycle works in this region.
From the above diagram, one can notice that there are three sources of water: direct
precipitation, overland flow and groundwater in the form of base flow. That’s why
there is still water in the river even though there is no rain for a long period of time.