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


What is the continuum of process dominance?



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


What is a tide dominated delta like?

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

-Ganges delta


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


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


 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)


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


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


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


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


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


What happened in this picture?

-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