Flooding Case Studies

Date: 16th - 21st of April 1927

Location: Almost all of the Mississippi Delta - Arkansas, Louisiana etc.

The Great Mississippi Flood of 1927 was the most destructive river flood in the history of the United States, with 27,000 square miles inundated up to a depth of 30 feet.

The flood began with extremely heavy rains in the central basin of the Mississippi in the summer of 1926.

By September, the Mississippi's tributaries in Kansas and Iowa were swollen to capacity.

Flooding overtopped the levees, causing Mounds Landing to break with more than double the water volume of Niagara Falls.

The Mississippi River broke out of its levee system in 145 places and flooded 27,000 square miles (70,000 km²).

This water flooded an area 50 mi (80 km) wide and more than 100 mi (160 km) long. The area was inundated up to a depth of 30 ft (9 m).

Short Term

• More than 23,000 square metres of land submerged
• 150 people died
• 637,000 forced to relocate
• Areas submerged in 30 feet of water
• Incredible damage to homes, buildings etc
• WHITE women and children rescued first

Long Term

• Took 2 months for the water to subside properly
• African-Americans switched political loyalty as they were treated horrendously by not only other survivors, but also rescuers - many were forced into becoming rescuers without pay
• The Red Cross provided food parcecls and set up refugee camps
• President Kalvin Coolridge did little/nothing

Date: July - September 1998

Location: Bangladesh is situated on the Ganges Delta flowing to the Bay of Bengal

Reason: 80% of Bangladesh is floodplain, and it has an extensive sea coastline, rendering the nation very much at risk of periodic widespread damage. Whilst more permanent defences, strengthened with reinforced concrete, are being built, many embankments are composed purely of soil and turf and made by local farmers

Physical Events

• Annual torrential rains - monsoon season + Relief rain from the Himalayas
• Meltwater coming from the Himalayas also efected the severity of the flooding

Human Vulnerability

• 70% of the land area is less than 1m above sea level
• 80% is situated on a floodplain
• Bangladesh is an LEDC so there is little money/resources to put into the development of flood protection
• A very large population - poor
• Deforestation

Short Term

• Capital of Phaka was 2 metres under water
• Two thirds of land area was covered by water
• 1,070 dead instantly(ish)

Long Term

• 30 million people homeless
• Death from disease increased due to the spread through water
• Lack of access to medical care
• 529 hectares of crops were destroyed
• 20% decrease in production
• 400 factories were closed

Date: 16th of August 2004

Location: The two villages of Boscastle and Crackington Haven in Cornwall

Boscastle was a high flood risk area before the storm event due to its unique flood prone physical characteristics. Physical characteristics included are impermeable bedrock, thin soil, lack of vegetation, very steep converging topography, many fluvial systems joining in a confined area, a temperate wet climate and land use. With the combination of high precipitation (orographic and frontall type rainfall) from the storm event, the timing of the high tide and the debris forming a temporary dam a serve large flood event was generated.

Physical Events

• 12 - 4pm 200mm of rain fell
• 2 million tonnes of warer flowed through the river
• Peak flow was about 140m/s
• The ground was completely saturated, increased speed of flow

Human Vulnerability

• Town was built at the point of confluence of two rivers

Short Term

• No fatalities
• 75 cars, 5 caravans, 6 buildings and several boats were washed into the sea
• Approx 100 homes and businesses were destroyed
• Trees were uprooted and debris were scattered over a large area
• Fleet of 7 helicopters rescued roughly 150 people hanging from trees

Long Term

• Tourist industry was severely damaged
• Huge insurance claims were made
• People's businesses suffered hugely
• Flood defences have been increased and improved
• Almost everything rebuilt or replaced

Date: 15th of August 1952

Location: Lynmouth, Exmor, Devon, South-West England

Reason:  It is thought that a cold front scooped up a thunderstorm, and the orographic effect worsened the storm. Debris-laden floodwaters cascaded down the northern escarpment of the moor, converging upon the village of Lynmouth

In 24 hours 9 inches of rain fell, flowed into rivers that came together in the narrow valley leading to Lynmouth.

FLASH FLOOD

Short Term

• 100 buildings were destroyed or seriously damaged
• 28 out of 31 bridges badly damaged
• 38 cars washed out to sea
• 34 people died
• 420 homeless

Long Term

• No water, gas or electricity supply
• £3-5million in repairs