Whenever water exceeds or soaks typically dry terrain, a flood occurs. There are not many locations on Earth where flooding is not a concern. A river can become overwhelmed and spread over the neighboring area with torrential rains, a damaged dam or embankment, abrupt icemelt in the highlands, or even a beaver dam in a susceptible location. Floods are becoming more frequent and intense, and global warming is predicted to increase extreme precipitation frequency and severity. So what is fluvial flooding? And have you wondered about the types of fluvial processes that are involved? Let’s learn more about this phenomenon.
1. What are 6 Main Causes of Flooding?
- The rate of rainfall is maximum because of tropical weather disturbances.
- Deforestation and Incorrect agriculture methods are major issues.
- Structures and drainage canals are improperly designed.
- Poor upkeep of drainage systems and obstruction from material brought by floodwater.
- Settlement in floodplains can be a big problem.
Rivers and streams, as well as drainage systems, naturally experience flooding. It happens when drainage systems are full, and rivers and streams cannot hold the extra water produced by severe weather. The drainage canals then go over their built-up or natural banks, allowing water to penetrate the nearby areas and cause flooding. Flooding danger is also increased by human activities that harm the environment, such as sand mining, deforestation, and improper rubbish disposal.
2. What are the 4 Types of Flood?
A. Fluvial flooding
A fluvial flood, also known as a river flood, happens whenever the water level in a river, lake, or stream increases and overflows onto the nearby coastlines, banks, and land. The increased water level could be the result of snowmelt or significant rain. When a river overflows, it can affect smaller rivers downstream, leading to the collapse of dams and dikes and the fluvial flooding of neighboring areas.
The quantity (output) of downpours in an area and their frequency and intensity influence the magnitude of a river flood. Other elements include the terrain encircling the river system and the water content of the soil as a result of past rainfall. Floodwater rises more slowly and is typically shallower in flatter terrain, where it frequently persists for days at a stretch.
B. Coastal flood
The flooding of land regions near the shore by seawater is referred to as coastal flooding. Storm surges, tsunamis, and high tides are frequently the culprits behind coastal flooding. Storm surge is the chief reason for coastal flooding and frequently the biggest threat a windstorm poses. It is created when strong wind gusts from a windstorm drive water onshore. This flood causes severe loss of life and property as water overpowers low-lying territory. The strength, magnitude, velocity, and course of the windstorm are some variables that affect how severe a coastal flood is. The geography of the onshore and offshore regions is also significant. Coastal flood simulations use this data to calculate the likelihood and size of a storm surge.
C. Pluvial flooding
When there is a flood without an overflowing water body, it is called a pluvial or surface water flood. It’s a popular misperception that flooding only affects areas close to bodies of water. However, pluvial flooding can occur anywhere, in both urban and rural regions, even when there are no nearby water bodies. Typically, there are two reasons why rivers flood:
- A heavy downpour overwhelms the urban drainage system. When the system is overloaded, water spills into the streets and neighboring buildings.
- Rainfall that falls on elevated terrains, such as hillsides, cannot be absorbed by the ground. Areas, where the recent forest fires are located on hillsides, are infamous for being sources of pluvial floods.
D. Flash flooding
Flash flooding occurs when the surface cannot take in the water as rapidly as it falls due to high and abrupt rainfall. Even though these floods typically pass quickly, they can be hazardous and act swiftly while they do. Efficient drainage systems and preventing urban sprawl on floodplains can reduce flash flooding. Must see How many Rivers are there in India?
3. What is Pluvial and Fluvial?
Pluvial and fluvial flooding can be defined as follows:
Fluvial flooding, also known as riverine flooding, happens when a river overflows due to prolonged periods of heavy rain. It’s also possible that ice blockages and rapid snowmelt bring it on. A river overflow can result in smaller rivers flooding downstream, which frequently causes dams and dikes to fail and saturate neighboring communities, causing extensive damage.
Riverine (fluvial flooding) floods can be divided into two categories:
- Overbank flooding occurs when the water rises and overflows the banks of a river or stream. This is perhaps the most typical type and can happen in channels of any size, from tiny streams to enormous rivers.
- Flash flooding is an abrupt, strong stream of water moving at a high rate of speed across an already-existing river channel. According to the Federal Emergency Management Association (FEMA), the most frequent flood event is fluvial flooding.
When torrential rains produce a flood event without the aid of an exceeding water body, the result is a pluvial, or surface water flood. One of the biggest myths regarding flood risk is that you must live close to a river or lake to be in danger. That misconception is disproved by pluvial flooding, which can occur in any metropolitan location, including higher elevation places above the river and coastline floodplains.
There are two typical forms of surface floods:
- An urban plumbing system becomes overwhelmed by heavy rain. When the system is overloaded, water spills into the streets and neighboring buildings.
- Rain that falls on highlands that cannot absorb the water causes runoff or streaming water. The prominent sources of pluvial flooding are hillsides with recent forest fires. Such are the features of such floods.
4. What are the 3 Types of Fluvial Processes?
Three different types of work are done by water moving through a river. The types of fluvial processes are briefed below:
A. Deposition
A fluvial deposition is a result of a natural phenomenon where the river cannot transport the sediments and other particles. Here the levees’ structures are formed because of heavy flood periods when the water overflows the streams and the river. Some sedimentary processes are carried out that start with sediments deposited with the flow of water.
B. Fluvial erosion is one of the types of fluvial processes is the separation of the riverbed and bank material. Erosion begins when water flow energy overcomes the material resistance of the riverside bed and banks. The relationship between stream energy and velocity hinges on the gradient and water depth.
There are two ways that fluvial erosion happens:
- Vertical erosion is the process through which a river deepens its substrate.
- In lateral erosion, a river’s bank corrodes. The river broadens as a result. This frequently causes major issues, such as the loss of agricultural fields. A lot of vegetation along the riverbank might avoid bank erosion.
C. Fluvial Transport
Stream load refers to the sediment cargo carried by a river. This one can be divided into three parts, each of which is conveyed via a different system:
- Ions, molecules, and atoms released from the solution of solids are known as a dissolved load. They’re transported in a solution.
- Sufficiently tiny solids retained in suspension are suspended loads. These are suspended and carried.
- Bedload is the sediment that is moved on the solid riverbed. Through friction and saltation, they are transferred.
5. What is Fluvial Flooding?
Fluvial flooding, also known as river floods, occurs when the water level in a river, lake, or stream rises and breaches onto the banks, coastlines, and adjacent land. It’s possible that heavy rain or snowmelt is to blame for the rising water level. Check out How can Reduced Precipitation lead to Limited Water?
6. How does Fluvial Flooding occur?
While rivers and streams overflow their banks and flood nearby low-lying areas, this is known as fluvial flooding (the natural floodplains). This can happen when a river channel is blocked or constrained or, in estuarine areas, when high tide levels prevent the river from flowing out into the sea. It can also happen when runoff from torrential rain exceeds the storage capacity of the river channel. Short, steep rivers can flood quickly, while longer, more gently flowing rivers can flood over time at a range from where the rain fell.
Various effects will result from variations in precipitation patterns, such as those that could be brought on by changing climate. Fortunately, there are ways to prevent fluvial floods.
7. What is the Difference between Pluvial and Fluvial Flooding?
Pluvial and fluvial flooding have their characteristic features. Even though they are generically referred to as floods, they can be differentiated as follows
| Pluvial flooding | Fluvial flooding |
| When the quantity of rainfall is greater than the ability of urban stormwater drainage infrastructure or the land to absorb it, pluvial flooding occurs. This extra water drains overland, collecting in low-lying places and hollows that are both natural and artificial, as well as behind barriers. Well before flood waters eventually penetrate a pipeline or natural drainage system, this happens as a swift reaction to strong Rainfall. | Once rivers and streams overflow their banks and overrun nearby low-lying areas, this is known as fluvial flooding (the natural floodplains). This can happen when a river route is obstructed, constrained, or, in estuarine areas, when high tide levels prevent the river from flowing out into the sea. It can also happen when discharge from heavy rain surpasses the capacity of the river channel. |
8. How can You prevent Fluvial Floods?
Rivers that are prone to flooding are frequently and carefully maintained in various nations to prevent fluvial floods.
- Levees, bunds, reservoirs, and weirs are utilized as defenses to stop rivers from overflowing their banks.
- If these fortifications fail, emergency measures like sandbags or transportable inflatable tubes are utilized.
- Coastal defenses like sea walls, beach replenishment, and barrier islands have been used to combat coastal floods in Europe and the Americas.
- Another means available to prevent fluvial floods is a dike. A dike reduces the likelihood of flooding compared to other measures. Although it can lessen the damage, it is preferable to integrate dikes with other flood mitigation measures to lower the danger of a dike collapse.
- The most common function of a weir, typically known as a low-head dam, is to produce millponds, which can be helpful as well.
9. How is Fluvial Erosion controlled?
Although river bank erosion is a persistent problem, some river bank control techniques for pluvial and fluvial can halt or at least slow down the process. Several people prefer to utilize natural materials to minimize river bank erosion since erosion happens in natural surroundings on the water. You can find everything from temporary, environmentally friendly materials to long-term remedies when looking at river bank recession prevention options.
A. Natural Plant Life
Riverbank erosion is significantly influenced by vegetation. In general, river sides with flora deteriorate less quickly than those without. This is because vegetation’s root systems typically strengthen the soil near the river bank, making the bank less susceptible to catastrophic breakdown. Additionally, during periods of intense rainfall, plants can serve as shock absorbers, inhibiting the growth of erosion.
B. Mats for soil erosion
A soil erosion mat is an additional popular alternative for erosion management. While wood fiber and straw are occasionally used to make these mats, coir coconut fiber is one of the most popular materials. This is due to the strength and naturalness of coir. Additionally, coir can withstand water for two to five years, contrasting straw or wood.
C. Cereal Logs
Coir logs are another coconut fiber-based technique for repairing river bank erosion. Because of their enormous diameter, coir logs are perfect for sustaining river banks or controlling erosion on slopes, shorelines, and other erosion-prone regions. Coir logs are large but simple to set in position. Once in place, they can aid in establishing vegetative growth.
D. Geotextiles
You can get geotextiles in a range of materials for several uses. Geotextiles made of woven or nonwoven synthetic fibers are one choice you have. Due to their extraordinary strength, woven geotextiles are well suited to manage enormous runoff and erosion control regions. Geotextiles made of nonwoven materials are permeable, making them perfect for drainage and sediment management locations. Geotextiles, including woven and nonwoven, are resistant to rot and UV damage since they are constructed of synthetic fibers.
E. Tree revetment
Small fallen trees are held horizontally along the river bank as part of a tree revetment system to control river bank erosion. The trees reduce the rate of erosion by slowing the water’s flow. Additionally, they stop sediment from flowing down rivers by catching it in the tree branches. The effective soil bed that this sediment then forms allows for the germination of natural flora.
F. Gabions
Gabions may be ideal for a river bed that necessitates a powerful and long-lasting erosion control solution. Large metal baskets called gabions are filled with crushed stone or concrete. They are the perfect answer for locations where significant soil erosion is prone to occur.
10. What are the Types of Coastal Flooding?
- Direct flooding occurs when the terrain is below sea level or height, and the waves haven’t produced any natural barriers, like dunes.
- When the water level is higher than the elevation of the barrier, during thunderstorms or high tides, water spills over the barrier. Flooding will occur on the opposite side of the barrier due to the water overflowing. One such restriction can be natural, like a mound, or artificial, like a dam.
- When water, typically in the form of massive, forceful waves, breaches a barrier, this occurs. Either it will weaken the barrier or it will demolish it.
In the last ten years, floods, droughts, tropical cyclones, heat waves, and powerful thunderstorms have been responsible for between 80 and 90% of all disasters caused by natural catastrophes. These above-mentioned pointers are the few types of flooding and this may be a man-made or natural barrier. (Also read How do Cataracts in the Nile River make Transportation Difficult?)
