Chapter 4: Fluvial Processes in Riparian Areas
Watersheds and Channel Networks
- Watersheds comprise all the area that drains to a lower elevation
such as a channel, stream, river, lake or other water body.
Watersheds can be large and small.
Figure 4.2. Different size watersheds and their typical channel network within a watershed. The numbers represent the Strahler stream order classification system.
- Classifying channels by flow
- Perennial flow occurs continuously with substantial
inputs from groundwater.
- Intermittent flow occurs for at least one month per year, generally in response to seasonally generated runoff. Flow is connected to groundwater from which it can receive substantial input.
- Ephemeral flow occurs only occasionally after
storms, and is typical of semiarid and arid environments.
Flow is not connected to the ground water.
Figure 4.3. Ephemeral, intermittent, and perennial channels in relation to the ground water table.
- Classifying channels by order (Figure 4.2).
- The uppermost tributaries farthest from the watershed
outlet are first (low) order streams, which join to produce
second order streams, which join to form third (higher)
order streams, and so on.
- A watershed can be roughly divided into three zones: the
headwaters, the transfer zone, and a deposition zone.
- Each zone has different characteristics.
- The headwaters zone typically contains low order
streams that are steeper and narrower.
- The
deposition zone contains higher order streams
that are wider and lower slope.
