Floods: The main causes, effects, and methods of control

No matter how prepared we are or how many precautions we take, sometimes disasters are just unavoidable. Even today, when the meteorological department is so much more accurate in its predictions than before, some natural disasters cannot be controlled, only managed.

Floods are one such calamity that can wreak havoc on residents without proper management. When dealing with such community concerns, the disaster management authorities and flood commissions in any area have a very important role to play.

To take effective measures, plan timely evacuation and relocation, recover from the damage, and sometimes even take precautionary measures, knowledge is crucial. Even at a community level, the more well-informed the citizens are about the causes, effects, and control measures for floods, the better.

Here is a guide to help you equip yourself with significant knowledge about floods and how to act in the face of this disaster:

Causes of floods

Essentially, flooding is an overflow of water in an area, and this can happen for several reasons.

1. Massive rainfall

An area’s drainage system, dams, and reservoirs are built to store excess water from precipitation, but sometimes, these also don’t have enough capacity and can overflow after massive rainfall. Heavy rainfall that exceeds the capacity of the drainage system causes flooding. The rainwater cannot be absorbed fast enough by the soil or cannot be contained in rivers and lakes as it normally does.

Moreover, urban flooding happens when the paved surfaces of urban areas cannot absorb the excessive water from the rainfall. Fortunately, measures can be taken to increase the storage and absorption capacity of any area. Professionals with a crisis management degree usually have the expertise and knowledge to undertake such preventative measures.

2. Geology of the area

Coupled with the risk of heavy rainfall, some geological aspects of the area increase the risk of flooding. Some rocks and soil types are more absorbent than others. Barren lands, highly sloped surfaces, and impermeable soil types – including clay and shale – increase the risk of flooding by increasing surface runoff.

3. Vegetation cover

A dense vegetation cover increases the absorption capacity of the soil; the roots of plants naturally absorb water. Forest cover also intercepts rainfall and increases lag time, minimizing the risk of floods. Therefore, barren and deforested land is at a greater risk of flooding.

4. Climate change

Climate change contributes to irregular rainfall, unseasonal snowmelt, excessive evaporation of water and precipitation, and parched soils that have a higher risk of flash floods. Global warming has increased the heat in the USA by an average of 1.8 degrees Fahrenheit since 1901! The increased temperature means that the atmosphere holds more moisture and results in more precipitation.  

5. Artificial causes

Human activities can reduce the absorption capacity of soils – for instance, pavement in urban areas contributes to urban flooding. Other times, floods result from flaws in human-made systems. A dam failure, for example, can cause a massive flood in the surrounding area.

Effects of flooding

Flooding can have devastating impacts on both the natural and human-made environments. More than 54 million people worldwide have been impacted by floods in the year 2022. Here are some effects of flooding:

1. Harm to human health and life

Data by Statista revealed that in 2022, flooding caused approximately 7,400 deaths across the globe and is considered the cause of some of the deadliest disasters in history. Drowning is just one way floods cause loss of life; indirectly, flood waters increase the death count by diseases like cholera and respiratory illnesses from mold and mildew in homes.

2. Property and infrastructure damage

The flow of flood water can bring down massive infrastructure, topple homes, damage roads, block transport routes, cut the electricity supply, and cause long-term structural damage. Repair of flooded land can take years, and even then, many communities are not able to restore the previous level of functioning.

3. Damage to the environment

The impacts of floods are not limited to humans and their environments; they inevitably cause serious damage to plants and vegetation, kill wildlife, and contaminate their habitats and groundwater supply. While floods can also enrich nutrients in the soil, negative impacts are often more severe.

Flood Water contaminates water bodies with the sediments it carries and causes algae blooms. Another major negative impact of flooding on the environment is erosion. Floodwater can cause serious erosion of riverbanks and alter the landscape.

4. Some positive impacts

Moderate and occasional floods have positive long-term impacts on the environment, too. Seasonal floods can renew ecosystems and replenish life-giving water supplies. Floods also bring nutrient-rich sediments that increase land productivity.

When flood water recedes, it provides the flood plains with natural fertilizers and provides valuable resources for civilization. It was in floodplains – i.e., areas of land next to a water body – and seasonally flooded deltas that ancient civilizations first developed.

Methods of control

Flood control generally involves two basic approaches: 1) preventing overflow of rivers by creating high earthen walls along the banks and 2) ensuring that excess rainwater has storage space in the form of reservoirs on rivers. The following are some measures to control flooding:

1. Building dikes or flood walls along embankments some distance away from and parallel to rivers. These help contain the flood water and keep it from flooding the surrounding land.
2. Construction of storage reservoirs and tanks upstream (as dams or bunds) to store excess runoff.
3. Creating diversion channels called floodways to redirect some of the river water to the branches and reduce the chances of overflow
4. Construction of terraces in highlands. A terrace is a ditch-like excavation meant to store runoff. These usually have a base of 1.5-2 m and are 12-20 cm high. Rainwater accumulates in these ditches until it gets absorbed into the ground. In this way, terraces can prevent soil erosion, recharge groundwater, and reduce surface runoff.
5. Increasing vegetation cover along banks and flood-prone lands to hold the soil together and absorb water runoff.

Final words

Flooding is one of the many devastating natural disasters that can, at times, not be avoided. Some areas are more prone to floods than others, and it is particularly necessary for them to take steps to control the risk and protect the residents. While flood prevention is not always possible, some measures, like the construction of dams, storage reservoirs, diversion channels, terraces, and afforestation, can help reduce the risk.