Case Studies: Contrasting Examples of Flood Mitigation (SL IB Geography)

Map of Jakarta, Indonesia

Map of Jakarta, Indonesia

• Jakarta is the current capital city of Indonesia

Causes of flooding

• It faces significant flooding challenges because:
• There is rapid urbanization
• Many parts of the city are below sea level 
• Many parts of the city have an average height of just seven metres above sea level
• The city experiences both tidal and river flooding
• About half of the city is sinking at a rate of nine inches per year
• Various factors affect the severity of flooding in the area:
• Intense rainfall
• Land subsidence
• Poor urban planning

Impacts of flooding

• On 1st January 2020, Jakarta experienced over 400mm of precipitation
• Ciliwung and Cisadane rivers flooded:
• In total, 66 people were killed
• Around 60,000 people were displaced
• In some parts of the city, floodwaters reached two metres
• Landslides in areas on the outskirts of Jakarta buried people and buildings
• Blackouts and lack of communication slowed the rescue efforts

Responses to flooding and mitigation

• Cloud seeding planes were used to increase rainfall over the oceans 
• This aimed to reduce the amount of rain over the land and therefore reduce flooding
• Over 11,000 health workers provided medical care
• Disinfectant sprayed to reduce the spread of disease
• Emergency shelters provided 
• Strategies to mitigate future flooding included:
• Widening and deepening the river channels to reduce flooding
• Construction of the East Flood Canal 
• Jakarta Emergency Dredging Initiative to increase the capacity of the rivers
• Creating more urban green spaces to reduce surface runoff and increase infiltration
• Creating an advanced warning system which uses real-time alerts for residents and businesses
• Community workshops for poorer communities living along the river to explain how to protect themselves from future flooding
• Preparation for disaster response, including megaphones, life vests and emergency kits

Map of River Severn

Map of River Severn

Causes of flooding

• Storm Ciara produced heavy rainfall of 75mm in 48 hours in February 2020
• Storm Dennis added 125mm falling in the Severn’s tributaries 
• The Met Office UK advised that February 2020 was the wettest on record
• Some areas experienced a month of rain in 24 hours

Impacts of flooding

• Over 1600 properties were flooded in the West Midlands
• Homes were evacuated
• Impact on transport infrastructure due to road and rail closures
• Financial impact on businesses

Responses to flooding and mitigation

• Nearly 30,000 warnings were given to property owners by the Flood Warning Service
• Over 380 staff from the Environment Agency and DEFRA responding to incidents across the Midlands
• Over 86 Aid staff from across the country helped manage the flood risks at pumping stations and prepare evacuation plans
• An incident room was set up to help people affected
• Demountable barriers used to help reduce flooding

Demountable flood barrier

• A pumping station helped reduce surface runoff
• Reservoirs being pumped down to reduce water levels
• Strategies to mitigate future flooding include:
  • £4.5million now being invested along the catchment area to reduce flooding
  • Construction of embankments
  • Additional culverts to let surface water out and stop river water coming in
  • Afforestation