Describe the processes that the river in sketches B and C would undergo to reach a graded state.

here are the solutions to the questions about river profiles:

1.1.1

The longitudinal profile of a river is a cross-sectional view of the river channel from its source to its mouth, showing the gradient or slope of the river bed.

1.1.2

Two characteristics of the longitudinal profile evident in sketch A are:

• It has a concave-upward shape, meaning it is steeper in the upper course and gentler in the lower course.
• It is smooth and continuous, without any abrupt changes in gradient like waterfalls or rapids.

1.1.3

Sketch A represents a $\boxed{\text{graded river}}$.

1.1.4

A graded river is in a state of dynamic equilibrium where the slope and channel characteristics are adjusted to transport the sediment load supplied from upstream. Sketch A shows a smooth, concave profile, indicating that the river's energy is balanced with its load, with no net erosion or deposition over time.

1.1.5

In sketch B:

• The temporary base level of erosion is the $\boxed{\text{lip of the waterfall}}$.
• The permanent base level of erosion is the $\boxed{\text{sea}}$.

Describe the processes that the river in sketches B and C would undergo to reach a graded state.

To reach a graded state, the river in sketch B (with a waterfall) would undergo headward erosion and vertical erosion. The waterfall would retreat upstream as the force of the falling water erodes the plunge pool and undercuts the resistant rock layer. Over time, the waterfall's height would decrease, and the gradient would smooth out, removing the irregularity.

The river in sketch C (with sediments) would adjust its profile through erosion and deposition. In areas of excessive sediment deposition, the river would increase its vertical erosion to deepen the channel and lateral erosion to widen it, thereby increasing its velocity and capacity to transport the sediment. This process would continue until the river's energy is just sufficient to transport its load, resulting in a smooth, concave profile where erosion and deposition are balanced.