Lecture 10

Question 1

Where do sediments come from?

Answer 1

Dependant on underlying geology, climate, and catchment size
Largest = Mountainous areas (uplift) + tectonic activity + high chemical weathering + precipitation
Tropical and subtropical regions
Smallest = Northern and polar regions (eg Canadian Shield rocks are granitic à hard and durable)

Question 2

How do sediments change the coastal environment?

Answer 2

Negative Effects
- Blankets floor + smothers organisms (shellfish) that need water
- Decrease light penetration - seagrass dies
- Water quality –> filter feeding organisms struggle
- Decrease coral reef coverage
Navigation + safety

Question 3

What is overall effect on the ecosystem from sediment deposition?

Answer 3

Negative Effect

Question 4

How do we monitor coastal sedimentation rates?

Answer 4

SET (Surface Elevation Table) Study - Andrew Swales
- to define subsidence component in measured SARs.
Found sediment first then mangroves. –> Can determine whether sea-level rise is accelerated or due to subsidence
Sediment = height of ground bed - base rock depth

CSI (Compound Specific Isotopes)
shows where sediment comes from à targeted management
Dating Techniques
- Lead 210, Carbon 14 dating
- Caesium (Cs)
- Pollen and Charcoal
- Volcanic Deposits (New Zealand)

Question 5

What are the problems associated with sediment monitoring?

Answer 5

Problem - Sediment accumulation = spatially heterogenous

Time of sediment slug release relative to the tide