Introduction
The work of flood control structures is designed to protect the community and the environment during floods. Dams, levees, and channels are examples of flood control facilities that reduce damage during floods and allow for a faster response to flooding situations.
Every year, floods cause problems on populated regions, killing lives and causing millions of dollars in damage, destroying communities and bringing local economies to an end. If you’ve ever been through one, you know how helpless it feels to be up against Natural Beauty. And if you haven’t, don’t suppose it can’t happen to you. Almost every major city in the world is susceptible to heavy rainfall and has areas at danger of flooding.
Fortunately, we’ve established techniques and structures throughout time to limit our exposure and risk. We still can’t control how much rain falls (at least in the short term), but we’ve discovered several techniques to manage that water once it hits the ground, reducing the risk to life and property.
We all understand what a flood is in general: too much water in one location at one time. However, I believe there is still some confusion regarding how floods occur. Part of the uncertainty, I believe, stems from the wide range of scales available when discussing flooding. The majority of river systems are dendritic. Because of the geography of the ground and long-term geologic processes, streams connect and concentrate as you go downstream, much like the branches of a tree.
Watershed
A watershed is the total region of land where rainfall gathers and drains into a single exit; it functions as a funnel. As you proceed downstream, those funnels begin to merge. As you travel further, the watershed grows in size as more and more streams contribute to the drainage. As a result, watersheds can be small or large. Your front yard is a watershed to the street gutter. If it rains heavily directly on your house, the gutter will flood and may even overflow into the street.
At the other end of the spectrum, the drainage area of the Mississippi River in the United States is over a million square miles (or three million square kilometers). A heavy rainstorm in one city will have little effect on the overall flow of this river. However, if the basin as a whole has an unusually rainy year, this might lead to significant floods when the water concentrates in a single stream. This is straightforward, yet knowing flooding, let alone controlling it, is a huge intellectual problem. Smaller watersheds only flood during violent storms known as “flash floods.” This water is usually already gone by the time the following storm arrives.
Large watersheds, on the other hand, flood as a result of heavy and continuous rain. Single storm occurrences have little impact on them. Of course, there’s everything in between in the dendritic system, which means a flood might be a small incident, affecting a few houses and streets for a couple of hours during a strong rainstorm, or a months-long misery affecting vast large areas of land in several villages.
Nonlinear nature
Revering flooding is also difficult due of its nonlinear nature. This is a simplified cross section of a river. The main channel is where most regular flows occur. Every unit of river rise does not result in that much greater area in inundation. Furthermore, there is little construction along the river’s banks, except from a few modest bridges and a few boats. However, things shift above the channel banks. The hills aren’t as steep, resulting in vast, flat stretches of land. And do you know what we prefer to do on large, flat spaces near waterways? We construct things, such as entire cities. You might also use it to describe a type of land.
levees
The issue is that once a channel over-banks, every unit of increase in the river equals significantly broader flooding extents. You can understand why this is referred to as the floodplain. In addition, a cross-sectional view reveals one of the most typical structural solutions to flooding levees. If over-topping the river’s banks is a problem, we may simply raise the river’s banks by constructing earthen embankments or concrete barriers. By limiting rivers within their constructed banks, levees safeguard built regions. As a result, places outside the levees will flood less frequently. It doesn’t imply they’re completely safe from flooding, because a severe storm may always overflow the levees. Over-topping of a levee can landslides and possibly failure (or breach) of the berm in earthen constructions. This might increase the floods even worse, especially if people were not removed from the region ahead of time.
Diversion canals
As a result, while levees are a relatively easy solution to flooding, they are not without problems. But sometimes just getting the water out of the canal is enough. Diversion canals are another proven and reliable flood control method. These are man-made channels that are meant to divert flood waters to less-developed regions where they will be less harmful. It is frequently impossible to enlarge an existing river due to current development or for environmental reasons. Instead, we build a separate canal to redirect floodwater away from built areas and into natural streams downstream. The head of most diversion channels will include some form of structure to assist control the course the water travels. Water will flow down the natural river under normal conditions, but when a flood occurs, most of the water will be diverted, limiting flood danger to built communities. However, it would be preferable if all of that water did not enter the river in the first place.
Dams
Dams, the other primary kind of flood control infrastructure, are the only way to do this. These are buildings designed to impound or store enormous amounts of water, so forming reservoirs.
Dams for flood management are maintained partially or totally empty so that when a significant flood hits, all of the water may be stored and released slowly over time. The theory isn’t too complicated here. We can’t modify the volume of water that arrives from a flood, but we can control how long it stays in the river with proper storage. Large sloshes of water into this bucket gently drain out over time. As long as the sloshes are spaced sufficiently apart and the bucket is large enough, there is usually never considerable flooding on the other side. However, not all dams are designed primarily for flood control. Many reservoirs are designed to be as full as possible so that the water may be used for hydro-power, city supplies, or agriculture irrigation. If a water supply lake is empty during a major flood, it will function similarly to a flood control pool, storing the water for later use.
If the dam is already full, they must release the floodgates to allow the water to flow. This might be frustrating for people downstream, who may have assumed the dam would protect them. A dam may often fulfill multiple functions at the same time. Different zones, known as pools, are developed for various functions. One pool is kept full to be used for hydro-power or water supply, while the other is kept empty to be utilized for flood storage. Finding the perfect balance between how much storage to maintain full vs empty is a difficult task that takes into account climate, weather, and the maximum quantity that can be discharged without causing damage downstream. Some dams modify the size of these pools throughout the year based on the seasonality of flooding, and some even use risk indicators such as the level of snowfall within the watershed to greatly help the volume available to store a possible flood.
Flood control
In this post, I’ve used the word “flood control.” However, the word is rapidly losing popularity. If you ask an engineer or hydrologist these days, they’re more likely to mention “flood risk management.” Our power to “regulate,” quote-unquote Mother Nature is insecure at best, and the more we try, the more we realize that, while expensive infrastructure is useful in many situations, it is, at best, an imperfect strategy for reducing the long-term effects of floods.
For example, flood control facilities (particularly levees) might protect some areas while increasing floods in others. For two, over-banking flows are helpful in a variety of ways.
Flooding, like wildfires, is a natural phenomena that has beneficial impacts on the floodplain, such as improved habitat, ecology, soil, and groundwater recharge. Third, we are increasingly realizing the real benefit of stability is, rather than lowering the probability of floods, we are reducing the effects.
This is often done by planned development, such as conserving (or converting) the floodplain for natural streams, parks, trails, and other uses that are less at risk of flooding. In fact, flood investments, in which high-risk property is acquired and turned to green space, are frequently the most cost-effective option to prevent long-term flood damage (even if not the most politically popular strategy).
We are unlikely to ever be able to lower the volume of rainfall during severe storms, and many areas are already experiencing more intense rainfall events than they have in the past due to climate change. However, we will continue to explore structural and non-structural solutions to lessen the risk to life and property caused by flooding.
CONCLUSION
Protecting cities against flooding is a difficult challenge, especially given that cities will house more than half of the world’s population by 2050. So, in order to improve urban flood protection, scientists have tried to identify methods to employ natural and sustainable solutions, both for building stronger structures than those now in existence and for educating people on how to use them effectively.