( Figure 9.11 Landforms of a youthful river on an OS map
09 V-shaped valley 08 08 Interlocking spurs 07 07 09
9
Waterfall
06
06 30 31 32 33 The mature stage (middle course)
During the mature (middle) stage, the river is now carrying a greater volume (amount) of water and as a result has more power. This is because tributaries or other rivers have joined it. Even though the gradient at this stage is not as steep as the youthful stage, the river is still eroding. It now erodes both vertically and laterally (sideways). Also, at this stage, the river is carrying more material in its load.
Meanders
Meanders are curves or bends in the river in its mature stage. Meanders are formed by both deposition and erosion.
Formation: • As the river reaches its mature stage it flows more slowly and lateral erosion occurs where there is a bend in the river.
• The hydraulic action of the river erodes the bank on the outside of the bend, as this is where the river is flowing the fastest. The bank is also undercut, further eroding the outside of the bend.
• Meanwhile, the eroded material is deposited on the inside of the bend where the river is flowing more slowly (as the river has to slow down on the inside of the bend).
Youthful river - page 141
• With time, the bend becomes more extreme and forms the shape of a loop.
Examples of meanders: Meanders are found on most rivers and can be seen in the middle courses of the rivers Shannon and Moy.
Erosion Deposition 34
: Figure 9.12 Formation of meanders
: Figure 9.13 Meanders on the River Moy in Co. Mayo 143
