Subject: Environmental Effects of Floods

I'm doing a report on the effects of flooding on the environment. Can you help me? What can people do to help ease flooding? I live in an area where flooding hardly occurs; What could I do to help people that live in those areas?

    You asked about the effects of flooding on the environment. This is a pretty broad question, but I'll try to provide some answers to what I think you are asking about.
    First, floods are part of the natural cycle of things. The benefits of natural floods almost certainly outweigh the negative aspects. The problems start when flooding occurs in areas of large-scale human development of the landscape.
    In areas largely inhabited by people, there are both positive and negative environmental effects of flooding. 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. 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.
    On the negative side, floods disrupt normal drainage systems in cities and typically overwhelm sewer systems. Thus, raw or partially raw sewage spills are common in flooded area. Additionally, if the flood is severe enough, destruction of buildings that can contain a large array of toxic materials (paints, pesticides, gasoline, etc..) can cause the release of these materials into the local environment, which is not good. I'm sure you could imagine other "negatives" similar to those I've just described.
    Floods disrupt many people's lives each year and personal tragedies due to flooding occur frequently. A wise society, in my opinion, would reap the benefits of flooding and avoid many of the negatives if they would choose to build cities in ways that can accomodate flooding without trying to avoid it. Attempting to go against nature is almost certainly a loosing prospect in the end.
    Flood prevention is really something left up to cities and towns. If where you live isn't flood prone, maybe there is some other natural hazard that does affect your area that you could learn about and help with instead. As individuals, if we all keep the minimum amount of toxic substances (paints, solvents, automotive fluids, etc..) around our homes, there will be less of these substances to "spill" when any sort of unfortunate natural dissaster befalls the communities in which we live.

Ken Rubin, Assistant Professor
Department of Geology and Geophysics
University of Hawaii, Honolulu HI 96822

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