r&b: tidal flats, marshes, and mangrove forests, sediment budgets, and human structures

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where are intertidal beaches found?

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1

where are intertidal beaches found?

commonly at estuarine/deltaic lagoonal environments (intertidal around lagoon; lagoon gets filled with sediment to form flat)

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2

sand flats

characteristic ripples; found low on beach because of strong currents (waves are stronger there)

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3

mud flats

very smooth; found high on beach because of weak currents (swash is weaker the further away from sea it ends up)

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4

what controls upward growth of tidal flats?

rate of sea level rise

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5

why is there an accumulation of sediment onto tidal flats/lagoons?

flood tides are stronger than ebb tides due to frictional interactions; more sediment transported landward than seaward

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6

do tidal flats have vegetation?

not really

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7

salt marsh

where intertidal is speckled with vegetation; home to many species of salt grasses

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8

where are salt marshes found?

temperate, subpolar, and polar regions

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9

where are mangroves found?

tropical regions

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10

why are so many species of salt grasses found in salt marshes?

there are many niches to be filled; zonation occurs in accordance to these niches

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11

how does the presence of vegetation affect the morphology of salt marshes?

buffers flow, reduces tidal current velocity, and enhances sediment accumulation

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12

mangroves

when intertidal at tropics are full of vegetation; home to many species of trees

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13

why are there so many species of trees in mangroves?

same reason there are so many grasses in marshes: many niches to be filled; zonation occurs as well

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14

why do mangroves have very unique root systems?

because mud they grow in is anoxic; roots find unique ways to get oxygen

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15

how does the presence of mangroves affect the morphology of the intertidal?

reduces water flow and accumulates sediment due to dense roots and trunks

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16

where can sedimentation occur only as fast as sea level rises in mangroves?

along the flat part of the forests; edge of the forests and edge of shore

<p>along the flat part of the forests; edge of the forests and edge of shore</p>
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17

where can sedimentation occur faster than how sea level rises in mangroves?

along the fringe (area closer to shore)

<p>along the fringe (area closer to shore)</p>
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18

why are mangroves so important for blue carbon?

most of their biomass is underground, meaning the carbon they store is underground, and thus can't be transferred into atmosphere

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19

why do coasts migrate?

in accordance to sea level changes, sedimentation changes, and shoreline erosion

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20

how are coasts and their barriers migrating overall today?

landward (sea level is rising)

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21

what is the current rate of sea level rise?

2-3 mm per year

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22

where do maritime forests occur?

along back of dunes, on barrier flats

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23

in terms of beach-scale, where are tidal marshes, mangroves, and tidal flats found?

near sea level on lagoon side of beach; get their water by washover during storm surge

<p>near sea level on lagoon side of beach; get their water by washover during storm surge</p>
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24

where are mud and peat found?

tidal flats, marshes, and mangroves; when beach migrates landward, deposits can be found poking out on ocean side of beach

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25

what are the three mechanisms for landward migration? (not sea level rise)

wind transport through/to dunes, tidal transport through inlets, and washover

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26

can inlets themselves migrate?

yes, in accordance to longshore transport

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27

do inlets close?

yes, old inlets close and new ones form all the time

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28

how are flood-tide deltas formed?

when tides move past inlets and deposit into lagoons, where velocity is low, depositing sand; forms land with distributary channels

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29

how are ebb-tide deltas formed?

when some sand reaches the lagoon during ebb tide and some sand leaves lagoon by ebbing currents; these are very small

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30

what two ways remove sand from longshore transport?

accumulation upstream and entrapment in flood-tide delta

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31

what happens when a longshore transport system is starved?

erodes downstream sides of land (this is why tidal inlets migrate for example)

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32

healthy beach

seaward expansion; can hold its position

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33

unhealthy beach

landward expansion

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34

what are five sediment sources for beaches?

longshore drift, cliff erosion, rivers, biogenic shells, continental shelf (from flood current)

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35

what are five sediment losses for beaches?

longshore drift, dunes, washover, tidal inlets, submarine canyons

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36

what kind of beaches are easier to erode?

finer grained beaches

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37

what are two human structures that have attempted to slow landward migration?

groins and jettys

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38

groin

huge rocks protruding seaward; erodes beach downstream (deflects longshore transport further down); make lose sediment to submarine canyons

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39

jettys

huge features that jut out sometimes for miles into sea; basically bigger groins; used to stabilize inlets

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40

what direction do winter winds blow during storm conditions in washington?

S/SW

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41

how have humans impacted erosion rates?

x10-100 increase in erosion

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42

how have humans impacted sedimentation rates?

x1/2 decrease in sedimentation

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43

breakwaters

structures that are parallel/subparallel to beach; has same issues as jettys/groins

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