Lecture 21- Estuarine geomorphology and processes I Flashcards Preview

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Flashcards in Lecture 21- Estuarine geomorphology and processes I Deck (40):

What is estuarine geomorphology?

-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


What are estuarine processes?

-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


Why is geomorphology important for zoology?

-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


What are the processes that drive hydrodynamics determined by?

-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


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

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


What are deltas and estuaries associated with?

-dynamic systems associated with the mouths of rivers


What are deltas composed of?

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


What are estuaries?

-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


What is the distinction between a delta and an estuary?

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


Where will deltas occur?

-in an estuary


How are deltas and estuaries a continuum?

estuary into delta


What is the definition of an estuary?

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


What is the definition of a delta?

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


How are deltas and estuaries members of an evolutionary continuum?

-balance between the three things

-so estuary can change into a delta

-regression= down sea level

-progression= up sea level

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What is the continuum of process dominance?


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

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


What are the three types of deltas?

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


What is a wave dominated delta like?

-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

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What is a tide dominated delta like?

-lot of channels due to inflow and outflow of the tides

-Ganges delta

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What is a river dominated delta like?

-Gulf of Mexico

-plumes of sediment far off coast

-cloudy area off the river is sediment being transported off the coast

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What is a tidal bore?

- 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


What happens to waves in estuaries?

-become asymmetrical, extreme case: tidal bore


How are estuaries divided according to tidal wave changes?

hypersynchronous, synchronous, hyposynchronous.


What is hyposynchronous estuary?

- 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

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 What is hypersynchronous estuary?

-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)

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Are ebb and flow often equal?

-no very unusual for them to be equal


What happens when you have shortened flood and lengthen ebb?

-have development of flood an ebb channels

-important in sediment plus nutrient transport and fish movement

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What are waves like and how do they impact estuaries?

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


What do fluvian process depend on?

-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


What is ebb?

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


What is flow?

-tide coming in


How do residual currents form?

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


How can we classify estuaries?

-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


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

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


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

-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

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

-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

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

-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

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What are the negative stratification estuaries like?

-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

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What happened in this picture?

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


What is important in forming deltas and estuaries?

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