In the middle of the night on 24 June 1852, a catastrophic flood swept through the New South Wales town of Gundagai. The water rose quickly to become a raging torrent that swept whole buildings away. Between 80 and 100 people died, and the disaster remains the deadliest flood in Australia's recorded history.
Floods occur when water covers land that is normally dry. The main cause of floods in Australia is heavy or long-lasting rainfall, which can make rivers exceed their capacity and overflow. In coastal areas flooding can be caused by tsunamis, very high tides, or tropical cyclones, which cause surges of seawater.
And now, the latest climate disaster involves water. Summer bushfires scorched more than one-fifth of the country's forests and killed at least 30 people, according to a new report. And now, flash floods in eastern Australia in recent weeks have left thousands without power in parts of Queensland and New South Wales.
Floods in Australia occur more frequently in the summer (December, January and February) than the winter months (June, July and August). Most of these summer floods occur in the northern parts of Australia. This coincides with northern Australia's wet season which runs from November-April.
Drought ($249.7 billion), severe storms ($247.8 billion) and inland flooding ($146.5 billion,) have also caused considerable damage. Severe storms have caused the highest number of billion-dollar disaster events (113), while the average event cost is the lowest ($2.2 billion).
A flood occurs when water inundates land that's normally dry, which can happen in a multitude of ways. Excessive rain, a ruptured dam or levee, rapid melting of snow or ice, or even an unfortunately placed beaver dam can overwhelm a river, spreading over the adjacent land, called a floodplain.
Flash flooding occurs within 6 hours of the rain event. Flooding is a longer term event and may last a week or more. Flooding along rivers is a natural and inevitable part of life. Some floods occur seasonally when winter or spring rains, coupled with melting snows, fill river basins with too much water, too quickly.
A flood is an overflow of water that submerges land that is usually dry. Floods can also occur in rivers when the flow rate exceeds the capacity of the river channel, particularly at bends or meanders in the waterway. Floods often cause damage to homes and businesses if they are in the natural flood plains of rivers.
Australia
| Date | Location | Fatalities |
|---|
| May 2015 | South – East Queensland Flash Floods | 5 |
| September 2016 | Central West and Riverina Floods | 1 |
| February 2017 | Western Australian Floods | 2 |
| Late March 2017 | Eastern Australian Floods caused by Cyclone Debbie | (As of 8 April 2017) 12 |
Three common types of flood explained
- Fluvial floods (river floods) A fluvial, or river flood, occurs when the water level in a river, lake or stream rises and overflows onto the surrounding banks, shores and neighboring land.
- Pluvial floods (flash floods and surface water)
- Coastal flood (storm surge)
10 measures to prevent (urban) flooding
- Create a 'sponge city'
- Green roofs/rooftop gardens.
- Create flood plains and overflow areas for rivers.
- Separating rainwater from the sewer system.
- Install water infiltration and attenuation systems.
- Keep the sewer system clean, so it can do its job.
- Sustainable drainage: permeable pavement, sidewalks and gardens.
The transformation of a tranquil river or normally dry wash into a destructive flood occurs hundreds of times each year, in every part of the United States. Every year, floods drive some 75,000 Americans from their homes; on the average, 127 persons are killed each year.
Heavy, intense rainfall can occur suddenly, and the quickly rising floods caused by this in the minutes or hours after the rainfall are known as flash floods.
Standing flood waters can also spread infectious diseases, contain chemical hazards, and cause injuries. Each year, flooding causes more deaths than any other hazard related to thunderstorms. The most common flood deaths occur when a vehicle is driven into hazardous flood waters.
Flash floods occur within a few minutes or hours of excessive rainfall, a dam or levee failure, or sudden release of water held by an ice jam. Flash floods can roll boulders, tear out trees, destroy buildings and bridges, and scour out new channels.
In general, two or three inches of rain per hour creates only minor street flooding. Yet if eight to 10 inches pours down in a hour or two, roads usually are severely flooded and canals overflow. That's when the National Weather Service issues flash flood warnings.
Common warning signs include intense rainfall, dam or levee failure as well as other events such as slow moving tropical storms and early snow melt can all contribute to flooding, whether you live in a flood zone or not.
Severe
flooding is
caused by atmospheric conditions that lead to heavy rain or the rapid melting of snow and ice.
What Causes a Flood?
- Heavy rainfall.
- Ocean waves coming on shore, such as a storm surge.
- Melting snow and ice, as well as ice jams.
- Dams or levees breaking.
Flood predictions require several types of data: The amount of rainfall occurring on a real-time basis. Knowledge about the type of storm producing the moisture, such as duration, intensity and areal extent, which can be valuable for determining possible severity of the flooding.
Flash floods can bring walls of water from 10 to 20 feet high. A car can be taken away in as little as 2 feet of water. To stay safe during a flood, go to the highest ground of floor possible.
Flooding occurs in every U.S. state and territory, and is a threat experienced anywhere in the world that receives rain. In the U.S. floods kill more people each year than tornadoes, hurricanes or lightning. What areas are at risk from flash floods? Densely populated areas are at a high risk for flash floods.
Flood water can be heavily contaminated with sewage and other pollutants. It can cause sickness and infections. If your house has been flooded and you have a well, don't drink the water. Household items that have been flood-damaged will have to be discarded according to local regulations.
Approximately, 21 million people worldwide could be affected by river floods on average each year, and the 15 countries with the most people exposed, including India, Bangladesh, China, Vietnam, Pakistan, Indonesia, Egypt, Myanmar, Afghanistan, Nigeria, Brazil, Thailand, Democratic Republic of Congo, Iraq, and Cambodia
Strauss estimates that 28,000 people living in 127 square miles of low-lying land are at risk of being flooded.
- 10 States Most at Risk of Flooding.
- Georgia.
- Massachusetts.
- North Carolina.
- South Carolina.
- Virginia.
- New Jersey.
- New York.
Several colonies in areas such as Nacharam, Mansurabad, Nagole, Karmanghat and other locations were inundated owing the flooding of nearby lakes. Water in Hussainsagar too exceeded full tank level, and is flowing through surplus nala towards Musi.
Rainfall together with synchronisation of very high flows of the three major rivers of the country in only three days aggravated the flood. Dhaka, the capital of Bangladesh, was severely affected.
