Morphology of Coastal Areas

Question 1

motivation

Answer 1

-coastline evolves due to environmental (storm erosion and SLR) and anthropogenic factors (coastal development and change in sediment transfer)
-needs to be known for coastal engineering (in costal areas) and coastal management (of environment, social expectations and response to climate change)

Question 2

sediment budgets

Answer 2

In: longshore and imports from rivers
Out: longshore and seaward due to storms

Question 3

dynamic equilbrium

Answer 3

balance of the budget
-coasts act as natural barrier against the ocean waves and inundation

stopped by
-decreased river sediments
-increased human activity @ coast
-humans change natural sediment flux
-climate change leads to increased storms and SLR

Question 4

natural coastal protection

Answer 4

winter=storm season
-larger waves which transport sediments down, making a shallower slope and a bar

summer=calm season
-has smaller waves which transports sediments up making a steeper slope and a berm

Question 5

coastal morphology

Answer 5

natural time varying behaviour of coast landforms and the mechanism that control it, varying with space/time scale

aims to understand the systems state @ a specific point in space and time and predict the future state of a specific point in space and time

Question 6

morpho-dynamic system

Answer 6

beach morphology (moveable bed) –> hydro-dynamics –> sediment transport –> beach evolution –> [back to start]

Question 7

coastal morpho-dynamic approches

Answer 7

deterministic
-attempts to capture large number of processes involved in the system with no specific system behaviour assumed
-reflects our understanding of he system
-produces process based models

behaviour oriented
-assumes a type of morphological feedback which minimizes the effect of external F
-system tends to an equilibrium configuration
-leads to semi-equilibrium models

Question 8

equilibrium beach profile

Answer 8

balance of destructive (erosion from gravity, braking induced turbulence or return flows) and constructive forces (beach forming wave asymmetry, onshore transport by wave induced velocities) acting on the beach
-dp/dx = 0 with p being sediment transport

Simplification
-assume the main destructive force is from wave breaking
-in equilibrium with a slope able to dissipate the waves energy
*large particle dissipate more E therefore can be stable in a steeper arrangement

Question 9

sea level rise

Answer 9

increased depth means a shallower slope
-erosion leads to a translation of delta x backwards
-profile is the same relative to the MWS so the coast must move up
-volume of the sand is constant, so ^ use the same amount of sand

Question 10

active profile width

Answer 10

where the waves can generate sand motion
-stops at d_cl
-[m]

Question 11

equilibrium bay shape

Answer 11

assumes a stable shore has Q_long=0 or partial dQ_long/dy = 0
-Q_long is the sediment transport // to the shore

empirical methodology
-ID control point and transition point
-measure beat and R0
-calculate Rn for a range of theta
-join the points