Coastal Hazards & Opportunities (Cambridge (CIE) O Level Geography)

Coastal Opportunities

• There are many opportunities that the coast can bring:

• Development including:

  • Homes

  • Shops

  • Hotels

  • Roads

  • Schools

  • Restaurants etc. 

• Nature reserves

• Swimming and sports

• Industry

• Fishing and aquaculture

• Tourism

• Agriculture

• Ports and harbours

Coastal Hazards

• Coastal hazards can be either natural or human induced

• Natural hazards include storms, flooding and tsunamis

• Human actions cause a variety of issues as shown in the table below:

Natural coastal hazards

• Coastal hazards arise from a number of factors:

  • Storm surges - a rapid rise in sea level caused by really low-pressure storms (e.g. tropical storm) 

  • Storm tides - occur when there is a combination of high tide and low-pressure storm

  • Tsunamis - large sea waves due to underwater earthquakes. The closer to the coast, the bigger the impact

  • King tides

  • Sea level rise due to global warming

  • High river discharge after a storm - when combined with a spring tide, water in the estuary cannot discharge into the sea causing a backflow of water and flooding

• Any number of these hazards bring coastal flooding 

• The biggest impacts are felt by emerging countries, although the biggest costs are to MEDCs

Tropical storms

• Hurricanes, typhoons and cyclones are all types of tropical storms, the only difference is where they form:

  • Hurricanes form in the tropical North Atlantic Ocean and Northeast Pacific

  • Typhoons form in the Northwest Pacific Ocean

  • Cyclones form in the South Pacific and Indian Ocean

• In the northern hemisphere they form between May and November

• Between October and May in the southern hemisphere

• A tropical storm can destroy coastal areas and kill people and the effects are worse in LEDCs due to lack of economic funds

• Other impacts are:

  • Destruction of buildings and infrastructure

  • Heavy rainfall and storm surges

  • Loss of ecosystems, trees, land, crops and animals

  • Ships are wrecked at sea and sunk

  • Power and communications are lost

  • Costs can run into the millions of $ and the effects are greatest in heavily populated areas

• Managing tropical storms is difficult but some of the ways to reduce the risks are:

  • Sea walls and artificial levees to prevent flooding

  • Evacuation plans for the population

  • Satellite tracking and early warning systems

  • Build homes and buildings to withstand strong winds 

  • Raise homes above storm surge levels and have strong shutters on windows

  • Emergency supplies and shelters

  • Have storm insurance

Changing sea levels

• Rising sea levels produce submergent coastlines, with rias and fjords

• Falling sea levels produce emergent coastlines, with relic features such as raised beaches, cliffs with caves, arches etc.

• Sea levels have risen and fallen many times in the past

• During the last Ice Age, sea levels fell as the water was locked up in glaciers and ice sheets, rising again as the ice melted

• Sea levels are linked to global warming and will have a significant effect on many low-lying coasts and islands

• Many Pacific Ocean islands, such as Kiribati and Tuvalu are at risk of being completely submerged by rising sea levels

• This issue is made worse as many of the world's densely populated areas are located on coastal lowlands

• New York and Miami in the US are major cities vulnerable to sea-level rise as the cities are built at sea level

Influence of geology

• Geology shapes the coastline over time, place and space

• A coastline made up of softer rocks such as sands and clays will be easily eroded by destructive waves to form low, flat landscapes such as bays and beaches

• Coastlines of more resistant, harder rock will take longer to erode and produce rugged landscapes such as headlands

• The differences between hard and soft rocks will also impact the shape and characteristics of cliffs

Erosion 

• The impact of erosion along the coast is seen globally, however, on local scale geology has the biggest effect

• Areas that are made of less resistant rock such as limestone, sandstone and boulder clay will erode faster than those coastlines made up of more resistant rock such as granite

• Longshore drift and destructive waves removing sand from beaches exposes the base of cliffs to higher energy destructive processes 

• Coastal management can increase rates of erosion further along the coast - using groynes to slow down longshore drift depletes sediment elsewhere and creates shallow beaches which exposes the shore to erosion

• Coastal erosion threatens many islands placing residents and tourist resorts at risk 

• Tourist and coastal developments all speed up the rate of erosion and remove natural coastal protection such as mangroves, coral reefs, sand dunes and salt marshes