BeachDune Systems

1
Beach-Dune Systems

• Chapter 15

2
Coastal Systems

• Relatively New (
• There was more Florida and shorelines were
  further offshore than now
• Sea level rise will greatly affect this in the
  future (and has already started)
• Florida has 1,350 miles of coastline

3
How Dunes are made
4
Topics to be researched

• How do dunes form--Dane
• How does vegetation stabilize dunes--Gena
• WavesI will do this in a few minutes--Chris
• Types of vegetationmajor vegetative components
  of dunes e.g. sea oats--Dom
• Effects of hurricanes on barrier islands--Layson
• Effects of invasives on vegetation--Kane
• Geologic history--Meaghann
• Effects of tides and how tides work--Deanna
• Sea walls, jetties,etc.pluses and minusesDoug
• Beach animalsDulcineah
• Role of crabs, invertsDeb
• Best natural beaches Steph
• Formation of other ecosystems affected by
  dunes--
• a) salt marsh
• b) maritime forest--Nesya

5
How do dunes form anyway?

• Wind deposited vs. water deposited
• Erosion vs. deposition
• Vegetation stabilizes dunes
• Living on dunes is tough
• Droughty
• Salty
• Windy
• Water erosion
• Dunes are ephemeral
• Wind erosion
• Different kinds of dunes
• Embryonic (nearest ocean)
• Amophila arenaria (marram grass) allows for sand
  to hold sand

6
Where are our beaches from originally?
7
Effects of Waves

• Erosion wont occur below ½ of wavelength
• Water 1/2 of wavelength does NOT move

8
Wave velocity A Little Physics

• Velocity L/P
• That is, wavelength/length of time it takes for a
  wave to pass
• Velocity of wave decreases as friction increases
• Period remains the same as it approaches the
  shore
• Wavelength shortens
• Waves break because height of wave becomes
  larger

What Happens Here?
9
Currents can make sand barsa new barrier island

• Waves break at 1-1.5 times the wave height.
• So 6 foot waves can make seafloor erosion happen
  in 9 feet of water.

10
(No Transcript)
11
Rip currents

• Figure A shows that when waves caused by strong
  onshore winds or distant storms move ashore they
  build up pressure on the sand bar

12
Rip currents
13
Rip Currents

• Figure C depicts the best escape from the rip
  currentswimming parallel along the beach. The
  good news is that rip currents are often more
  narrow than lengthy. Remain calm, and swim your
  way out of the current.

14
Longshore currents

• Usually on long, straight beaches
• http//www.geography-site.co.uk/pages/physical/coa
  stal/longshore.html
• http//intranet.lissjunior.hants.sch.uk/water/pics
  web_ks2geography/flash/g2reswa0015.swf

15
Rip currents also kill people
16
Problems Beach Erosion

• Overdevelopment has lead to severe erosion (to be
  explained in a minute)
• Permitting to build is rampant of 4,965
  requests to build, only 52 were denied by DEP!
• Erosion rates dont matter, permits keep coming

17
Beach erosion

• Over 50 of our beaches (400 miles) are eroded
• 300 of the 400 are critically eroded

18
Beach Nourishment

• In west-central Florida, 65 is critical erosion
  area
• One solution beach nourishment
• Beach nourishment costs about 1 million/mile and
  typically needs to be done every 4 years

19
Other solutions

• http//coastal.er.usgs.gov/wfla/video/vidphotos.ht
  ml
• Rip rapbut wheres the beach? Under a bunch of
  rock

20
Sea level rise

• http//video.on.nytimes.com/ifr_main.jsp?nsida-6c
  63a12710ee32b89d77d7afr_storyc22cf1df8b67096c7
  606bb00e12eb6e853c538bast1163455983508mpWMPcp
  ftruefvn8fr111306_051304_w6c63a127x10ee32b89d
  7x7d7brdm327244.21716337453

21
Sea walls
22
So-called solutions

• Sea walls
• Groins
• Rip rap
• Or combinations of these

23
Jetties

• Which way is longshore drift occuring

24
The real solution

• More public beach
• Less private beach
• Stop development
• Period

25
(No Transcript)
26
Hurricanes and sea level rise