Physical geography U6th
Tropical revolving storms:
o Don’t form on equator because of Coriolis effect
o Roughly between 5-30 degrees N or S of equator
o Form over warm ocean
o Travel E – W
o In N hemisphere deflect north. In S hemisphere deflect south
Formation
,Hurricane structure
Storm surges
- Wind circulation in eye of hurricane blows surface
of ocean
- This causes vertical circulation in deep ocean.
- Once the hurricane reaches shallower water near
the coast, vertical circulation is disrupted.
- The water has nowhere else to go but up and
inland
- Storm surge occurs where winds blow onshore
- The highest surge tends to occur where the
strongest winds are (radius of maximal winds).
- Low pressure of the storm
Hurricane Katrina
August 2005
Moving from E – W
Moved into Gulf of Mexico ( in size) hit New Orleans as level 3/4
Wind speeds of 120 mph
Primary impacts Secondary impacts
5000 km2 forest + woodland destroyed Contaminated water supply
Flooding from 25ft storm surge 3 million without water
230,000 left unemployed
1836 ppl killed
,Overhead power lines brought down
Reasons for bad impacts:
End of summer - sea was very warm
An anticyclone pinned Katrina over Gulf of Mexico (warm ocean fuelling storm)
New Orleans – sinking + low sea level – made of silt, soil and clay
New Orleans – wetlands not replenished – can act as coastal defence
Large areas of New Orleans is poor, Katrina hit before social security payments the poorest couldn’t
afford to evacuate. Poorest also lived in low lying areas.
Management and response
Prediction:
- National hurricane centre director gave call to mayor for evacuation. (prediction led to preparation)
- The hurricane centre warned that New Orleans was in category 4 path 3 days before.
- Storm surge was underestimated
- Ran hurricane simulation to test levees + said levees would fail but this was ignored.
- Public could have been given a 12 hour earlier warning more daylight hours for evacuation
lengthening evac time could mean larger areas than necessary = evacuated traffic + ppl at risk
from this.
- Prediction = v accurate (15 miles off)
Protection:
- 125 mile-long system of levees built by US army to protect after hurricane Betsy 1965
- 23 ft floodwall along Mississippi river
- In New Orleans, installed I-walls rather than T-walls (v expensive $1 million). I-walls are less stable +
could only withstand cat 3.
- Levees put in front of wetland = bad because wetland = natural protection.
- Levees to small 17th street canal – first street to fail
Preparation:
- Mayor delayed emergency evacuation
- School buses in parking lots + not used to assist evac
- 11 million litres of water staged at strategic locations
- Delayed evac hundreds of deaths because people could not find ways out of city.
- 80% of city evacuated = good
- Location of supplies + water was not good couldn’t be distributed.
Immediate response:
- 80% of city evacuated
- Deliberately breached levees to drain water into wetlands
- Set aside Superdome for 10,000 ppl
- Contaminated water sent into wetlands
- Superdome was understaffed + there was reports of rape
- Poorest communities couldn’t evacuate
Long term response:
- Building floodproof housing + levee height
- Gov offers insurance for new raised housing
, - Levees already eroding due to being rebuilt with soft soil
- Experts question reliability of pumps to expel rainwater
- Unplanned patchwork recovery some houses raised some not
- Broadmore multimillion pound drainage system prevented some levees from being breached.
Typhoon Haiyan
November 2013
Philippines – NEE urbanising but 50% live rurally
150 mph winds
Cat 5 when hit landfall (Tacloban 1st hit)
Primary impacts Secondary impacts
70,000 hectares farmland flooded $5.8 billion cost
20ft storm surge 6000 ppl died
Heavy rain landslides 1.9 million left homeless
Disease outbreaks
Reasons for bad impacts:
70% of Philippines have been deforested interception lag time floods
Onshore winds amplified winds + storm surge
Tacloban’s funnel shape amplified storm surge
Low lying + densely populated areas = 2-3m above sea level.
Management and response
Prediction:
- Hazard maps underestimated storm surge flood zone
- Very little technology to effectively make forecasting
- Forecasting improved significantly since Haiyan, especially with storm surges because of
improved international cooperation in sharing data + atmospheric modelling.
Protection:
- Many mangrove forests removed would’ve acted as natural flood defence
- Very little flood protection in Tacloban
- New homes being built on ground risk of flooding from storm surges + flooding
- Cyclone shelters constructed to improve local resilience.
Preparation:
- Serious lack of education of residents about storm surges, ppl didn’t evacuate
- Despite prediction wasn’t translated into appropriate action
- Warnings done on bikes with megaphones (ignored)
Immediate response:
- Tacloban city convention served as evac centre
- Security checkpoints in place
- US deployed hospital ship
- Tacloban centre = low lying many ppl drowned
Long term response:
- $500 million of donations
Tropical revolving storms:
o Don’t form on equator because of Coriolis effect
o Roughly between 5-30 degrees N or S of equator
o Form over warm ocean
o Travel E – W
o In N hemisphere deflect north. In S hemisphere deflect south
Formation
,Hurricane structure
Storm surges
- Wind circulation in eye of hurricane blows surface
of ocean
- This causes vertical circulation in deep ocean.
- Once the hurricane reaches shallower water near
the coast, vertical circulation is disrupted.
- The water has nowhere else to go but up and
inland
- Storm surge occurs where winds blow onshore
- The highest surge tends to occur where the
strongest winds are (radius of maximal winds).
- Low pressure of the storm
Hurricane Katrina
August 2005
Moving from E – W
Moved into Gulf of Mexico ( in size) hit New Orleans as level 3/4
Wind speeds of 120 mph
Primary impacts Secondary impacts
5000 km2 forest + woodland destroyed Contaminated water supply
Flooding from 25ft storm surge 3 million without water
230,000 left unemployed
1836 ppl killed
,Overhead power lines brought down
Reasons for bad impacts:
End of summer - sea was very warm
An anticyclone pinned Katrina over Gulf of Mexico (warm ocean fuelling storm)
New Orleans – sinking + low sea level – made of silt, soil and clay
New Orleans – wetlands not replenished – can act as coastal defence
Large areas of New Orleans is poor, Katrina hit before social security payments the poorest couldn’t
afford to evacuate. Poorest also lived in low lying areas.
Management and response
Prediction:
- National hurricane centre director gave call to mayor for evacuation. (prediction led to preparation)
- The hurricane centre warned that New Orleans was in category 4 path 3 days before.
- Storm surge was underestimated
- Ran hurricane simulation to test levees + said levees would fail but this was ignored.
- Public could have been given a 12 hour earlier warning more daylight hours for evacuation
lengthening evac time could mean larger areas than necessary = evacuated traffic + ppl at risk
from this.
- Prediction = v accurate (15 miles off)
Protection:
- 125 mile-long system of levees built by US army to protect after hurricane Betsy 1965
- 23 ft floodwall along Mississippi river
- In New Orleans, installed I-walls rather than T-walls (v expensive $1 million). I-walls are less stable +
could only withstand cat 3.
- Levees put in front of wetland = bad because wetland = natural protection.
- Levees to small 17th street canal – first street to fail
Preparation:
- Mayor delayed emergency evacuation
- School buses in parking lots + not used to assist evac
- 11 million litres of water staged at strategic locations
- Delayed evac hundreds of deaths because people could not find ways out of city.
- 80% of city evacuated = good
- Location of supplies + water was not good couldn’t be distributed.
Immediate response:
- 80% of city evacuated
- Deliberately breached levees to drain water into wetlands
- Set aside Superdome for 10,000 ppl
- Contaminated water sent into wetlands
- Superdome was understaffed + there was reports of rape
- Poorest communities couldn’t evacuate
Long term response:
- Building floodproof housing + levee height
- Gov offers insurance for new raised housing
, - Levees already eroding due to being rebuilt with soft soil
- Experts question reliability of pumps to expel rainwater
- Unplanned patchwork recovery some houses raised some not
- Broadmore multimillion pound drainage system prevented some levees from being breached.
Typhoon Haiyan
November 2013
Philippines – NEE urbanising but 50% live rurally
150 mph winds
Cat 5 when hit landfall (Tacloban 1st hit)
Primary impacts Secondary impacts
70,000 hectares farmland flooded $5.8 billion cost
20ft storm surge 6000 ppl died
Heavy rain landslides 1.9 million left homeless
Disease outbreaks
Reasons for bad impacts:
70% of Philippines have been deforested interception lag time floods
Onshore winds amplified winds + storm surge
Tacloban’s funnel shape amplified storm surge
Low lying + densely populated areas = 2-3m above sea level.
Management and response
Prediction:
- Hazard maps underestimated storm surge flood zone
- Very little technology to effectively make forecasting
- Forecasting improved significantly since Haiyan, especially with storm surges because of
improved international cooperation in sharing data + atmospheric modelling.
Protection:
- Many mangrove forests removed would’ve acted as natural flood defence
- Very little flood protection in Tacloban
- New homes being built on ground risk of flooding from storm surges + flooding
- Cyclone shelters constructed to improve local resilience.
Preparation:
- Serious lack of education of residents about storm surges, ppl didn’t evacuate
- Despite prediction wasn’t translated into appropriate action
- Warnings done on bikes with megaphones (ignored)
Immediate response:
- Tacloban city convention served as evac centre
- Security checkpoints in place
- US deployed hospital ship
- Tacloban centre = low lying many ppl drowned
Long term response:
- $500 million of donations
