Lecture 8: Coastal Hazards Flashcards
Passive Margins
Coastline is distant from plate boundary
- wide continental shelves, sandy beaches
- barrier islands ie: East coast of North America, Arctic
Active Margins
Coastline is relatively close to plate boundary
-rocky shoreline and sea cliffs ie: BC
Waves
- made by wind blowing over water
- size depends on !) velocity of wind 2) duration of wind, 3)fetch, which is the distance wind blows over water
Wave height
-trough to crest distance
Wave Length
Distance between successive crests
Wave Period
Time that successive crests pass reference point
Wave Motion
Circular motion that moves downward from surface, diameter decreasing with distance as energy is decreasing
-shallow water becomes more eliiptical as it feels the bottom
Swells
- Waves generated by storms far out to sea
- can be predicted based on velocity, fetch, distance of waves
- approaching land, waves decrease in speed and wave length, and increase in height
Plunging Breakers
form on steep beaches; very erosive
Spilling Breakers
develop on wide, gentle beaches, less erosive
Tidal Bores
Waves that form when in flowing todal water is slowed by outflowing river water
Sea CLiff/ Sea Bluff
Erosional landform that marks landward boundary of beach
Berm
Onshore portion of beach that is flat, formed by sediment deposition
Beach Face
Onshore portion of beach that slopes seaward, lies within swash zone
Swash Zone
Where waves repeatedly rush up and back
Surf Zone
Area where waves move towards shore once they break
Breaker Zone
area where incoming waves peak and break
Longshore Bar
Ridge on seafloor in breaker zone
Longshore Trough
Depression on seafloor by wave action, landward of longshore bar
Beach Drift
sand moves in zig zag pattern in swash zone
Longshore drift
transport sediment by currents that flow parallel to shoreline
Spits
ridges that extend parallel to shore from point on land on a coast
Barrier Islands
Long narrow islands separated from mainland by bay/lagoon
Eustasy
global sea level fluctuations due to melting ice sheets
Isostasy
Forces that raise or lower the Earth’s Crust that change sea levels
Rip Current
Horizontal Current that flow away from shore
-occurs when water piles up between swash zone and longshore bar; breakage in longshore bar caused water to rush out
ERosion
Sea Cliffs and bluffs erode with waves, water, landslides
-most intense with high winds/water levels
Linkages of Coastal Hazards to Other Hazards
EQ, volcanoes, Tsunamis-> affect shoreline
FLoods, storm surges, -> erosion
Eroding cliffs -> landslides
NAtural Service Functions of Coastal Hazards
- scenic bluffs/coastlines
- beaches maintained with deposition
- coasts bring tourists
Human Interactions with Coasts
-removing sand dunes in barrier islands leaves them vulnerable for storm surges
Hard Stabilization
1) Sea Wall: protects but causes erosion at base
2) Groin: captures sand from longshore drift but erosion occurs downdrift
3) Break water: protects boats
4) Jetties: protects river mouthes
Soft Stabilization
-adding sand to nourish beaches
E-line
expected shoreline after certain number of years
E-zone
Area between current shoreline and E-line
Land Use to Minimize Damage
-coastal buildings should be temp. but developers only see money
Hybrid Disasters
Combination of natural and technological disaster
Technological Disaster
Human made devices causing disasters, worst is those with industry/transportation
Cumulative Effects
effects that worsen over time
Calculating Risk of Large Scale Structures
Probability of failure during lifetime of structure
Calculating Risk of Transportation
Probability of death/injury per km travelled
Calculating Risk of Industry
Probability of death/injury per person per hour exposed
Radon
- comes from decay or Uranium in rock
- inhaled it becomes polonium which lodges into lungs and causes damage
- colourless, tasteless, odourless
Radiation
-can be inhaled/ingested
-Direct Effects: within days
Indirect Effects: mutagenesis to offspring
-Delayed Effects: cancer
-comes from 1)tailings from mining Uranium, and Nuclear Reactors
Nuclear Reactor Meltdowns
accident that results in damage from overheating
- fuel rods tirn to liquid, walls of reactor core melt
- hot liquid melts bottom and seeps into floor/soil
Three Mile Island Nuclear Accident
- one of two reactors in Pennsylvania had valve break that control coolant
- radiation leaked
- worst disaster in the U.S… wussys
Chernobyl Nuclear Accident
- flawed design, operator error, disregard for safety lead to explosion
- 30 died immidietly, 2500 deaths due to thyroid cancer
- worst in the world
Titanic
sunk on first voyage
- hit a glacier
- death toll was high because there were not enough safety boats
Exxon Valdez Spill
- oil tanker hit the side of rocky reef in Alaska
- 75 million litres spilled
- remote location made recovery very difficult
Deepwater Horizon Oil Spill
- oil rig exploded with methane gas
- 8.5 million litres a day were released for 5 months
- extensive damage to wetlands/beaches
- tourism indistry faced loss, BP oil company blamed
- happened due to cost cutting choices in maintenance and they did not have a safety system
Mineapolis Bridge Collapse
- excessive weight form vehicles, concrete, construction vehicles
- 13 died
Tacoma Narrows Bridge Collapse
High winds caused collapse of suspension Bridge, there were no trusses for wind to go through
Challenger
- Cold weather lowered resiliency of rubber O-ring
- lead to release of gas = failed rocket booster
- 7 astronauts died on launch
Columbia
- during launch a piece of insulation broke off from external tank
- struck left wing, damaged heat protector
- disintegrated upon re-entry
