Cyclones/Hurricanes.
What are the effects of cyclones on the natural environment?
Tropical cyclones and Hurricanes can greatly effect the natural environment in a number of ways. The winds, storm surges,
torrential rain and floods which can be caused by this extreme natural event all can provide potentially hazardous. In this
essay I am going to use the case studies of Hurricane Katrina which struck the Gulf Coast of the United States of America
and Cyclone Heta which damaged islands in the south-west pacific in particular Niue.
Hurricane Katrina which struck the USA Gulf Coast August 28th 2005 was a category 5 hurricane which bought
about strong winds which gusted over 300 km/h. These winds were damaging to Gulf Coast region which includes the
states of Louisiana, Alabama, Mississippi, Texas and Florida the worst. The winds whipped up the seas on the coastline and
demolished tree’s ripping foliage off many plants. It also provided salt spray off the ocean which poisoned foliage stinting
plant growth.
2500mm of rainfall fell over New Orleans during Hurricane Katrina this added to the substantial flooding that
occurred in the region as it raised the river levels of the Mississippi river which New Orleans borders. Flooding was one of
the biggest causes of damage during Hurricane Katrina.
The storm surge that was created by the low pressure system of hurricane Katrina caused the most damage. On
its way into the path of the Gulf Coast the 8.5 metre storm surge crossed paths with the Chandeleur island which are just
off the coast. These island were home to a number of plant and animal species however they were completely demolished
by the massive surge of water. Out of all the states which were affected by Katrina New Orleans was the worst hit.
New Orleans had 560km2 of Marshland on its coastal border which once again had a number of animal and plants living
within it. This marshland was completely transformed into water by the storm surge and is still underwater. Much of New
Orleans has been built below sea-level with Lake Ponchartrian and the Mississippi river bordering the city. Natural Levee’s
in the form of stop banks have previously stopped the city from being flood by a deluge of rain however to bolster the city
up additional levee’s were built. These levee’s were said to be able to stand up to the affects of a hurricane however the
failed terribly in the face of hurricane Katrina. The Levee’s were breached in 53 places which caused 80% of the city to
become flooded. This flooding killed substantial animal and plant life and spread into freshwater ways causing salinisation
and contamination of the fresh water ways of New Orleans.
Cyclone Heta which hit the small island nation of Niue on the 6th of January 2006 also had substantial effects on Niue’s
natural environment. Niue is a small Coral Atoll of only 256 square kilometres and it is located at around 19 degrees
latitude in the south pacific ocean. Niue is not only very small but it is also very flat with its highest point being only 68
metres above sea level. This makes Niue extremely prone to flooding and when Heta struck that is exactly what happened
the mass of rainfall and the 4-7 metre storm surge with waves up to 10 metres high which were travelling it 100 km/h
washed inland. They bought with them coral which had been removed from reefs some of which were located 200 metres
below sea level. The coral deposition on the beach front was extensive as was the salinisation of the fresh water supply
which occurred due to the storm surge washing inland. The storm surge demolished vegetation along the coastline and
eroded banks on the North western side of Niue.
Wind also played a large part in damaging the small atoll. Winds lashed the low island stripping off 80% of the
foliage Coconut trees and other fruit trees were wiped from part of the island. The wind also contained a salt which burnt
those tree’s which survived the 300km/h gusts of wind which eventually killed all the foliage of the most affected tree’s
anyway. This presented Niue with a large fire risk as there was a large drought after the cyclone struck. This affected
Niue’s economy as it was largely dependant on the export of fruits and fishing.
Cyclones and Hurricanes can have large effects on the natural landscape. The Gulf Coast of America is now a
different environment than it was prior to Katrina striking and Niue is only gradually recovering with the remainence of
Heta still visible. They can strip tree’s , flood land, erode banks and change the shape of the land within hours providing a
very dangerous natural hazard.