Lecture 21- Estuarine geomorphology and processes I

Question 1

What is estuarine geomorphology?

Answer 1

-The study of estuaries as landforms: how they got there, how they operate, and how will they evolve -The interaction of processes and how they control the system

Question 2

What are estuarine processes?

Answer 2

-Waves, tides, river flow and currents -change is associated with tide levels and sea levels -main process are detrmined by its location -have combination of river, sea and land -inflow and outflow (ebb) -also sediments brought there -barrier -tiddes= have strong control over salinity in the estuary -river flow= controls the flow of freshwater into the estuary -if weak flow= the mouth may close into the estuary

Question 3

Why is geomorphology important for zoology?

Answer 3

-the landforms are what the ecology and biology exists on -sediments that compose the landforms are the primary habitat -species have preferences for different habitats, so species distribution changes as habitat changed both spatially and temporally -sediments are important sinks, stores and sources of nutrients and pollutants

Question 4

What are the processes that drive hydrodynamics determined by?

Answer 4

-The processes that drive hydrodynamics are also determined by the morphology of the landscape. -the wave tide and flow are also influenced by the topography

Question 5

What is a resident time of a sediment and what does it indicate?

Answer 5

-resident time of sediment= how long it stays -indicated the rate of change in the estuary

Question 6

What are deltas and estuaries associated with?

Answer 6

-dynamic systems associated with the mouths of rivers

Question 7

What are deltas composed of?

Answer 7

-river-derived sediment -Deltas form from deposition of sediment carried by a river as the flow leaves its mouth.

Question 8

What are estuaries?

Answer 8

-tidal-influenced lower parts of river and their valleys -a semi-enclosed coastal body of water, which has a free connection with the open sea, and within sea water is measurably diluted with freshwater derived from land drainage

Question 9

What is the distinction between a delta and an estuary?

Answer 9

-mouth can be closed off by sediment -delta only from the river -estuary is both marine and from river

Question 10

Where will deltas occur?

Answer 10

-in an estuary

Question 11

How are deltas and estuaries a continuum?

Answer 11

estuary into delta

Question 12

What is the definition of an estuary?

Answer 12

-The tidally influenced lower parts of catchments where a river enters the ocean

Question 13

What is the definition of a delta?

Answer 13

-An area of sediment deposition as a river flows to the ocean!

Question 14

How are deltas and estuaries members of an evolutionary continuum?

Answer 14

• balance between the three things
• so estuary can change into a delta
• regression= down sea level
• progression= up sea level

Question 15

What is the continuum of process dominance?

Answer 15

-

Question 16

What are the two types of estuaries? (based on physical classifications of mixing)

Answer 16

1. Wave dominated 2. Tide dominated (higher proportion of tide energy) (3. River dominated= she didn’t say it but it is)

Question 17

What are the three types of deltas?

Answer 17

1. RIver dominated 2. Wave dominated 3. Tide dominated

Question 18

What is a wave dominated delta like?

Answer 18

• nile delta
• rich form around the edge
• this is due to the higher proportion of wave energy, they pick it up and deposit in a line

Question 19

What is a tide dominated delta like?

Answer 19

• lot of channels due to inflow and outflow of the tides
• Ganges delta

Question 20

What is a river dominated delta like?

Answer 20

• Gulf of Mexico
• plumes of sediment far off coast
• cloudy area off the river is sediment being transported off the coast

Question 21

What is a tidal bore?

Answer 21

• a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travels up a river or narrow bay against the direction of the river or bay’s current. - have several waves on the edge of the estuary, they converge and push into the estuary -huge wave

Question 22

What happens to waves in estuaries?

Answer 22

-become asymmetrical, extreme case: tidal bore

Question 23

How are estuaries divided according to tidal wave changes?

Answer 23

hypersynchronous, synchronous, hyposynchronous.

Question 24

What is hyposynchronous estuary?

Answer 24

• very sharp decrease in amplitude up estuary from high bottom friction. ex. - Delaware Bay
• tidal range decrease with the river -friction or depth is the dominant over the width

Question 25

What is hypersynchronous estuary?

Answer 25

- bottom friction and shoreline convergence causes a loss of tidal energy. - tide rises in amplitude, amplification, before falling at the mouth of the river, ex. Bay of Fundy - the width is the dominant factor over the depth - as you move upstream have increase in tidal amplitude (height and power)

Question 26

Are ebb and flow often equal?

Answer 26

-no very unusual for them to be equal

Question 27

What happens when you have shortened flood and lengthen ebb?

Answer 27

- have development of flood an ebb channels - important in sediment plus nutrient transport and fish movement

Question 28

What are waves like and how do they impact estuaries?

Answer 28

-usually high energy -can erode the beach profile -transport salt water into the freshwater bit of the estuary

Question 29

What do fluvian process depend on?

Answer 29

-depends on amount of rainfall in the catchment, how large the catchment is (the contributing area into the river) -also the gradient= if steeper then more water

Question 30

What is ebb?

Answer 30

-is the movement of a tide back toward the sea.

Question 31

What is flow?

Answer 31

-tide coming in

Question 32

How do residual currents form?

Answer 32

-from the mixing of fresh and salt water -salty water more dense -results from the densities and temp differences

Question 33

How can we classify estuaries?

Answer 33

-on the basis of the degree of mixing -how well is the salt water mixed with the freshwater -important for biology, different organisms have different salinity ranges in which they can live

Question 34

What are the 4 types of estuaries based on the degree of mixing?

Answer 34

1.Highly stratified (salt wedge) estuaries 2.Moderately stratified (partially mixed) 3.Non-stratified (well mixed, vertically homogeneous) 4.Negative stratification

Question 35

What are the highly stratified (salt wedge) estuaries like?

Answer 35

- Greater river flow - Occur commonly in deep estuaries - Sediment dominated by river - very clear layers of freshwater and salt water - fresh on top as less dense - form where greater amount of river flow, occur in estuaries that are deep, fjord type valleys - sedimentation is dominated by river sediments so more mud etc. - can be 100s of meter deep - numbers= salinity value -0= fresh

Question 36

What are the moderately stratified (partially mixed) estuaries like?

Answer 36

- most of estuaries are like this - tide energy has greater proportion -less drastic change in salinity - Majority of estuaries - Shallow, tides overcome fluvial flow - Stronger ebb at surface, flood at depth

Question 37

What are the non-stratified (well mixed, vertically homogeneous) estuaries like?

Answer 37

- Tides fully over come fluvial flow - Shallow, wide estuaries of have lateral differentiation of salinity - non stratified, no distinction in freshwater and saltwaer - salinity almost the same as you move vertically - further inland the salinity value will increase or decrease - wide mouth

Question 38

What are the negative stratification estuaries like?

Answer 38

- inverse relationship here, salinity is higher at the mouth - this is where it is dry, lot of evaporation, common in australia - occurs in arid areas, high evaporation

Question 39

What happened in this picture?

Answer 39

-the mouth closes off, that evaporates -salty -anoxic = no oxygen -build up of nuntrients

Question 40

What is important in forming deltas and estuaries?

Answer 40

-Tide, wave and fluvial processes are important as well as the underlying topographic setting