Sediment Budgets

Answer 1

oil spilled on a coastline gets deposited on a beach, since the oil is heavier than the sand, it gets burried

Question 2

deadmans island

Answer 2

the skull came from a cemetery, they didnt know there was a cemetery, the sand eroded and exposed the cemetery

sand being eroded from glacial period dunes, sand moves along the shoreline (littoral driftlines - shows the direction sand moves along the shoreline)

bridge and marina entrance blocks the source of material to deadmans island area. area started eroding super rapidly

Question 3

define sediment budget

Answer 3

sediment budget:
Quantification of deposition and erosion of sediment between source and sink

where the excess&deficits of sands are

Defined for a littoral cell and for some control volume

Source of sediment
Sink for sediment
Transport Pathway between source and sink

Sediment does not move continuously and directly from source to sink- transport is episodic and reversible
-> over the long term it goes from source to sink

Question 4

what determines if there is erosion or deposition in a sediment budget

Answer 4

Erosion and deposition depend on the
gradient in sediment transport

q in > q out => deposition

q in < q => out

q in = q out => equilibrium

Question 5

sediment budget eqn for shoreline change for 2d vs 3d

Answer 5

2d:
𝚫V = 𝚫x * 𝚫y * h
𝚫V = the amount of erosion/deposition
𝚫y = length along the shoreline
𝚫x = amount changed in the cross-shore
h = depth of closure = no net volumetric change is observed

3d:
dx = (q in - q out) for x (cross shore gradient)
dy = (q in - q out) for y (longshore gradient)

𝚫V = dV/dt = dx/dt + dy/dt
∆𝑉 = (q in − q out ) ∗ dt

Question 6

barrier breaching

Answer 6

breaking of the barrier
-point pelee has been constantly breaching for the last hundred years
-episodic
-> breaching at high water levels, correcting at low water levels

breach started to heal itself even though water levels are high
-high water levels make supply
-erosion means deposition, we just dont know where

Hillman Marsh
-breach formed, no recovery because of rock walls, breach stays open

Question 7

source: river

Answer 7

moving sand down the coast

Question 8

sink: mangroves

Answer 8

force deposition, mangroves continue to grow and grow

Question 9

what processes are involved in barrier budget (5)

Answer 9

Multiple process-linkages and
feedbacks define beach erosion
and barrier response to sea level
rise and intensified storminess

1. Nearshore-beach interaction
2. Beach-dune interaction
3. Inlet morphodynamics
4. Overwash processes
5. Longshore transport

Question 10

how is dune formation affected by beach sediment budget

Answer 10

-sediment is needed to build the dunes. If less sediment is available, less sediment can go into making the dunes.
Dune budget is low if there is a highly positive or negative beach budget

dune budget is highest when the beach is in equilibrium

a neutral (or slightly negative) beach budget leads to the largest dunes.

a positive budget causes progradation of the shoreline, preventing sediment from accumulating in one location to form dunes

A negative budget will result in too little sediment supply to form large dunes.

A slightly negative budget is preferred for the largest dunes as it aids the inland transfer of sand

Question 11

how does describe the positive
feedback caused by shoreline erosion

Answer 11

Shoreline erosion creates a positive
feedback that leads to dune decay and
barrier translation through overwash

shoreline erosion depletes dunes

dunes protect against erosion, so dune depletion makes the beach more vulnerable to erosion
dune depletion lowers the height of the dunes, causing overwash, removing sediment from the beach sediment budget
this creates greater shoreline erosion, depleting the dunes even more