Deposition + Sedimentation

Question 1

What are the causes of deposition?

Answer 1

• shallowing of gradient: dec. V + energy
• dec. in volume of water in channel
• inc. in friction between water + channel

Question 2

What does the Hjülstrom curve show?

Answer 2

• relationship between material size + V
• weather material will be transported, eroded or deposited
• larger material = higher V needed to keep particles transported
• settling V curve = point material no longer has energy required to be transported so is deposited

Question 3

What are the 3 important features on Hjülstrom curves?

Answer 3

• smallest + largest particles require high Vs to lift them
• higher Vs required to pick up than for transport
• when V falls below a certain lvl, particles are deposited

Question 4

How does velocity needed to pick up particles vary w size?

Answer 4

• larger particles (gravel) = higher Vs bc are heavier
• sand = lowest Vs for entrainment bc of small size + non-cohesive nature
• clays = higher Vs for entrainment bc are v. cohesive