Floods are just as much a natural disaster as forest fires, but just as in fires, there is reason why these things happen. Once the violence subsides, nature begins the restoration process that will end up benefiting the area in a way that it would not have done if left alone.
Floods are part of the natural cycle of life. The benefits of natural floods outweigh the negative aspects. The problems begin when the floods happen in densely populated areas.
According to Ken Rubin, Assistant Professor at the Department of Geology and Geophysics of the University of Hawaii, Honolulu, "Floods can distribute large amounts of water and suspended river sediment over vast areas. In many areas, this sediment helps replenish valuable topsoil components to agricultural lands and can keep the elevation of a land mass above sea level."
A real world example: "An example of the latter case is the Mississippi delta. Before the Mississippi and associated rivers were controlled in levees in southern Louisiana, the rivers would frequently spill their banks. This processes made the lands of the Mississippi delta. This area is slowly subsiding with time and without the continued replenishment of sediment from river floods, much of it has dropped to elevations below natural sea level. Thus, one could say that not allowing floods is negative for this area. Our society has chosen instead to create a vast and complex system to keep Mississippi waters from reaching these lands. The lands remain dry but each year they subside more, making it ultimately more and more difficult to keep that way."
The negative side of flooding, outside of the obvious human toll, is the overwhelmed sewer systems. Raw sewage spills are common in flooded area. Also, when buildings are destroyed, especially old construction, a lot of dangerous materials are released into the water and transferred across the whole area and eventually enter into the ocean. Pesticides, petrol, asbestos and paints are the most common types of materials that are found in flood waters.
Some people believe that the way to alleviate the damage that floods cause is to build towns so that they can withstand them. They say that floods are natural and if we let them take their course, will benefit the land rather than ruin it. The down side is that it would cost billions of dollars to put high risk towns and counties on stilts. So we have to weigh the option of paying to recover land or double the cost to prevent the damage from happening.
