How is drainage density calculated?

How is drainage density calculated?

• A. Total length of all streams in the basin divided by the basin area
• B. Basin area divided by the total length of streams
• C. The average stream length times the number of streams
• D. Basin width divided by river length

Answer: (A)

Drainage density measures how densely a watershed is drained by its streams. It is calculated by taking the total length of all streams in the basin and dividing it by the basin area. In other words, it’s the amount of channel length per unit area, often expressed as km of stream per km2 of land. So you would add up every stream segment within the basin (the entire stream network) and divide that total length by the basin’s area. For example, if the combined length of all streams is 600 km and the basin area is 1200 km2, the drainage density would be 0.5 km of stream per km2. Reasons this approach is correct: it directly quantifies how much channel present relative to the land area, which reflects how quickly runoff can be routed through the network and how the landscape is dissected. The other formulations don’t produce this measure: they mix up units or rely on quantities that don’t represent channel length per area.

Drainage density measures how densely a watershed is drained by its streams. It is calculated by taking the total length of all streams in the basin and dividing it by the basin area. In other words, it’s the amount of channel length per unit area, often expressed as km of stream per km2 of land.

So you would add up every stream segment within the basin (the entire stream network) and divide that total length by the basin’s area. For example, if the combined length of all streams is 600 km and the basin area is 1200 km2, the drainage density would be 0.5 km of stream per km2.

Reasons this approach is correct: it directly quantifies how much channel present relative to the land area, which reflects how quickly runoff can be routed through the network and how the landscape is dissected. The other formulations don’t produce this measure: they mix up units or rely on quantities that don’t represent channel length per area.