To determine the relationship between the speed of water flow and the size of material it can carry, we can refer to a concept known as stream competence. Stream competence is the maximum particle size that a stream can transport. This ability is directly related to the velocity of the water flow; higher velocities can carry larger particles, while lower velocities can only transport smaller particles.
To better understand this relationship, consider the following general observations:
1. High-Velocity Flows:
- When the flow velocity is high (fast-moving water), the stream has greater energy. This increased energy allows the stream to pick up and transport larger particles, such as pebbles and cobbles.
- For example, during heavy rains, flood conditions, or steep river sections, the stream velocity increases significantly, allowing the stream to carry larger materials downstream.
2. Low-Velocity Flows:
- Conversely, in areas where the flow velocity is low (slow-moving water), the stream has less energy for transportation. Hence, it can only move smaller particles such as silt and clay.
- In slow-moving sections of a river or during periods of low water flow, the stream can only carry fine sediments.
To connect the flow velocity with particle sizes:
- Pebbles (e.g., size around 70 cm): Require very high flow velocities to be transported.
- Sand (e.g., size around 0.5 cm): Requires moderate flow velocities for transportation.
- Silt and Clay (e.g., size around 0.05 cm and 0.01 cm or smaller): Can be transported by low flow velocities.
The relationship can be summarized as:
- High stream velocities enable the transport of larger particles.
- Low stream velocities are capable of carrying only smaller particles.
Thus, the competence of a stream is heavily influenced by its velocity: faster-moving water has the potential to transport larger and heavier particles, whereas slower-moving water can only carry finer and lighter sediments.
