Floods are common type of natural disaster and it occurs when an overflow of water covers land that is usually dry. Floods can result in a devastating condition; from loss of lives and properties to critical public health infrastructure. Flooding can occur anywhere and can be due to various reasons. Nigeria’s flooding is mainly human-induced with poor urban planning practices and poor environmental infrastructure as contributing factors.
Types of Floods
The common types of flooding are:
- Flash Floods: This type of flood covers a relatively small area. They can be fast-moving waters that sweeps away everything in their path with little to no notice. This type of flood is caused by sudden and heavy rainfall that is not quickly absorbed on ground as quickly as it falls. This type of flood can move large objects like cars, trees, etc.
- River Floods: This occurs when the body of water exceeds its capacity. That is, the body of water exceeds the river banks. This is typically caused by high and heavy rainfall over a prolonged time.
- Coastal Floods: This occurs when waves, heavy rainfall, severe storm or tides causes accumulation of water on land. Coastal areas are areas that are close to oceans, therefore, they are at risk of experiencing flood.
- Groundwater Floods: This occurs as a result of drainage systems getting filled up with water by significant rain, which cause water to overflow into streets and nearby properties.
- Urban Floods: This occurs when the city does not have a drainage canal or sewage system to drain away the amounts of rain that are falling. Here, roads can be blocked because there is no drain to collect the water.
Causes of Flood
The causes of flood include:
- Heavy rainfall
- Overflowing rivers
- Poor drainage system
- Lack of vegetations that can help retain water
- Storm surges related to hurricane
- Broken dams: If dams that are designed to hold water upstream collapse, there will be discharge of more water downstream, resulting in flooding.
- Snowmelt: Warmer temperatures can melt snow. When a significant amount of packed snow on the ground around homes or nearby is melted, they can lead to flooding in streets and neighborhoods.
Effects of Floods
Floods can affect humans, human’s health, livestock (farm animals), environment and the country’s economy.
The effects of floods on Humans include:
- Loss of human lives
- Damage to or loss of properties
- Loss of livestock or loss of wildlife habitats
- Destruction of crops for feeding
- Deterioration of health from waterborne diseases
The effects of floods on Health can lead to:
- Hypothermia: A drop in body temperature below 35oC
- Animal bites
- Acute asthma
- Infections e.g., wound infection, Tetanus, Skin infection
The effects of floods on Economy include:
- Loss of productivity
- Depleted human capital due to loss of skilled workers
- Loss of land value
- Loss of livelihood e.g., due to destruction of buildings or properties
- Reduced working hours, which eventually lead to losses in gross domestic product
Control of Floods
Control of floods includes the methods involved in preventing or reducing the effects of flood. The methods include:
- Afforestation: This involves planting of vegetation to retain extra water. Avoid unnecessary cut down or burning of trees in forest.
- Construction of dams, reservoirs to help collect and hold waters when they reach a certain level.
- Terrace slopes: Terracing increases surface roughness and reduce runoff and erosion by slowing rainwater to a non-erosive velocity.
- Building floodways (man-made channels to divert water from flooding).
- Proper and clean drainage systems in houses, streets and communities to allow proper flow of water during rainfall.
- Ensure proper waste disposal to allow adequate flow of water on lands and in drainages.