Of flood risk and climate change




Rivers have been a very important part of human history: They provide food, freshwater, and fertile land for agriculture. While water is essential to life, if left unchecked its fury can be destructive. When rivers flood, the effects can be disastrous and the results are often fatal.

Climate change is increasing the risk of floods globally, particularly in coastal and low-lying areas, because of its role in extreme weather events and rising seas. The increase in temperatures that accompanies global warming can contribute to hurricanes that move more slowly and drop more rain, funneling moisture into atmospheric rivers like the ones that led to heavy rains and flooding in California in early 2019.

Meanwhile, melting glaciers and other factors are contributing to a rise in sea levels that has a created long-term, chronic flooding risks for places. More than 670 U.S. communities will face repeated flooding by the end of this century, according to a 2017 analysis; it’s happening in more than 90 coastal communities already.

On August 1, 1993, the Mississippi River at St. Louis crested at 49.58 feet, the highest stage ever recorded. The size and impact of the Great Flood of 1993 was unprecedented and has been considered the most costly and devastating flood to ravage the U.S. in modern history.

The Central China flood of 1931, for example, was one of the worst flooding events in recorded history. The Yangtze and Huai Rivers broke their banks, killing as many as several million people. There are few places on Earth where flooding is not a concern. Any area where rain falls is vulnerable to floods, though rain is not the only cause.

Although some theories argue that flooding has positives such as the transporting of vital nutrients such as nitrogen, phosphorus, and organic material, to the surrounding land. When the water recedes, it leaves sediment and nutrients behind on the floodplain. This rich, natural fertilizer improves soil quality and has a positive effect on plant growth, thus increasing productivity in the ecosystem.

Popular fertile floodplains such as the Mississippi Valley, the Nile River Valley in Egypt, and the Tigris-Euphrates in the Middle East have supported agriculture for ages because annual flooding has left tons of nutrient-rich silt deposits behind; Floods can replenish underground water sources. Floodwater gets absorbed into the ground then percolates through layers of soil and rock, eventually reaching underground aquifers; Floods can trigger breeding events, migrations, and dispersal in some species; Floods can boost fish stocks and brings life to wetlands;
The other theory says the human cost of flooding is disastrous and out ways the positives.

Some negative effects of flooding include: It harms wildlife- Flooding can have a negative effect on wildlife, causing drowning, disease proliferation, and habitat destruction; It causes sedimentation and erosion- Floodwater can also alter the landscape, for instance, by eroding riverbanks and causing them to collapse; Floods carry contamination-Floodwater can be contaminated with pollutants such as agricultural pesticides, industrial chemicals, debris, and sewage.

If contaminated floodwater enters the ocean, it can affect water quality and disrupt delicate ecosystems; Floods Spread Diseases-Floods are the leading cause of weather-related infectious disease outbreaks. Flooding events increase the chance of spreading waterborne diseases, such as hepatitis A and cholera.

Nigeria has recorded flood disasters yearly and we always reference the 2012 flood as the worst flood the nation recorded recently. Unfortunately, the nation is yet again in 2022 battling its worst floods in a decade with more than 300 people killed.

According to Nigeria’s National Emergency Management Agency, the flood has affected 27 states and the capital city Abuja. Half a million people are affected including 100,000 displaced and more than 500 people injured. The disaster has also destroyed thousands of hectares of farmland, worsening fears of a disruption of food supply in Africa’s most populous country. Jigawa state has recorded 91 deaths from flooding this year — more than any state in the country.

The Nigeria Hydrological Services Agency in its annual flood outlook defines the major causes of flooding in Nigeria as follows: soil moisture, extreme weather conditions owing to climate change, how dams are functioning especially those close to the country’s borders, and topography.

Flood prevention and control
Humans have increased the risk of death and damage by increasingly building homes, businesses, and infrastructure in vulnerable floodplains.

To try to mitigate the risk, governments should mandate that residents of flood-prone areas should vacate the areas or set construction requirements aimed at making buildings away from water ways.
Nigeria should make a massive effort to mitigate and redirect inevitable floods by adopting an ambitious engineering effort, such as the New Orleans’s extensive levee system and massive dikes and dams in the Netherlands.

Some other common techniques used for flood control are the installation of rock beams, rock rip-raps, sand bags, maintenance of normal slopes with vegetation or application of soil cements on steeper slopes and construction or expansion of drainage. Other methods include dykes, dams, retention basins or detention.

Although following 2005-Hurricane Katrina disaster in the United States, some areas prefer not to have dykes as flood controls. Communities have chosen to improve drainage structures with detention basins.

Some methods of flood control practiced for decades include planting vegetation to retain excess water, terrace slopes to reduce slope flow, and building alluviums (man-made channels to divert water from flooding), construction of dykes, dams, reservoirs or holding tanks to store extra water during flood periods.

However, it is best to combine dykes with other flood control methods to reduce the risk of a collapsed embankment. When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are to be used. Coastal floods have been controlled in Europe and North America with defenses such as ocean walls or barrier islands that are narrow, long strips of sand usually parallel to the coastline.

Floods are a force of nature, and their consequences, both positive and negative, are strongly felt by affected ecosystems. Climate change continues to put pressure on vulnerable areas leading to destructions to humans and the natural environment. Whether you regard floods as good or bad, one thing is certain: The world would be a safer place if the government will take the recommended actions above. May the souls of the departed rest in peace.

Maiyaki writes from Kaduna via
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