# Use the following formula to calculate the stream density of each sub-basin

Use the following formula to calculate the stream density of each sub-basin

Drainage basins (16.8 Arbogast 2nd. Ed.).

Notice the two sub-basins that are highlighted. The smaller one is the Willamette River watershed and the larger one is the Snake River watershed. The drainage density of a basin measures how well a watershed is drained and depends largely on the underlying bedrock and topography of the basin. Basins with high relief and exposed bedrock tend to have a higher drainage density.

Use the following formula to calculate the stream density of each sub-basin (show your work):

In other words, the [drainage density] equals the [total length of all streams] divided by the [area of the drainage basin]

Double-click and select Snake All Streams.

Double-click and select Willamette All Streams.

Willamette River watershed:

The area of the Willamette River sub-basin is 11,500 square miles.
The total length of all streams in the Willamette River sub-basin is 12,800 miles.
Question 16: What is the stream density of the Willamette River sub-basin?

A. 12800 / 11500 = 1.11

B. 11500 / 12800 = 0.90

C. 12800 / 11500 = 1.43

D. 11500 / 12800 = 0.95

Snake River watershed:

The area of the Snake River sub-basin is 108,000 square miles.
The total length of all streams in the Snake River sub-basin is 138,000 miles.
Question 17: What is the stream density of the Snake River sub-basin?

A. 108000 / 138000 = 0.78

B. 138000 / 108000 = 1.28

C. 108000 / 138000 = 0.83

D. 138000 / 108000 = 1.48

Collapse and uncheck WATERSHEDS AND DRAINAGE DENSITY folder.

DRAINAGE PATTERNS

Expand the DRAINAGE PATTERNS folder.

Figure 4. Drainage patterns (16.7 Arbogast 2nd Ed.).

The drainage patterns of a stream system (a network of streams and tributaries) depend largely on the topography on the land as well as the structure of the underlying bedrock. Areas subject to faulting often produce rectangular drainage patterns, while areas with folded topography (mountains) often have trellis drainage patterns. Volcanoes typically form radial drainage patterns. Dendritic drainage patterns are common in areas with non-porous, impermeable bedrock.

Double-click and select Drainage pattern 1.

Question 18: Identify Drainage pattern 1:

B. Trellis

C. Rectangular

D. Dendritic

Now that you have identified Drainage pattern 1, double-click and select drainage patterns 2 to 5 to identify them.

Question 19: Identify Drainage pattern 2: