Mississippi Floods: Missing Natural Sponges

May 15, 2011 By Arati Rao
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Everything is connected. All actions have consequences. All consequences teach lessons. Case in point: the Mississippi floods, rivers, natural floodplains, wetlands and destruction. And what lesson is it teaching us?

The flooding woes

Water levels in the Mississippi river are extremely high. This river originates in the state of Minnesota and flows all the way down meeting the Gulf of Mexico, in the state of Louisiana. Heavy rains in the north have been the cause and the communities living along the river bank are seeing the “worst flooding in eighty years.”

Levees and spillways which were constructed half a century ago are containing the water in some places but not in all. Levees are huge walls, like a dam, that are built along a river to contain the water level. Spillways are gates that can be opened in levees to release the water when the level gets too high. The Army Corps of Engineers decided to blast an earthen levee in the state of Missouri to prevent high waters from reaching major cities. But this will inundate (drown) about 130,000 acres of rich farmland and destroy about 90 homes.

It was not meant to be this way. Could this have been prevented? These are questions being asked and there are some very good answers. We simply have to listen and learn.  

Where are our natural sponges?

Flood-control structures like levees and spillways have been necessary only because the natural control for floods has been taken away. What do we mean? Well, there are these areas called “watersheds.” These areas contain the land’s drainage. The rivers, lakes, and streams surrounded by natural spill-zones (area around the rivers where water is allowed to overflow) are together called “wetlands.”

When snow melts or it rains very heavily and rivers overflow, these areas – including marshes and forestlands – act as sponges.  They absorb the water, remove the contaminants and slowly release it into the groundwater system and nearby streams. These wetlands help the levees do their work. It is a natural system built by nature to control the effect of floods. 

Now, what has happened in the last century? Such wetlands all over the world have been “disappearing.” How? Well, we have been “reclaiming” them for farms, houses and other human activity. As a result, there is no place for the excess water to go. Which means our levees will have to be stronger and we have to hope that the levees hold and rivers don’t run very high. Wetlands are the most productive ecosystems on earth. And we have lost about 80% of our wetlands in many states - and the destruction is continuing. 

Lessons to learn

The US floods in 1993 and 2008 caused levees to break and immense loss due to flooding. And even then people said that they would need to “learn from it” and protect and restore wetlands so that annual floods do not affect human habitation. But, even more wetlands have been “reclaimed” since 1993 for human activity! And in 2011, the losses continue. Restoring wetlands will control floods better – in addition to engineering responses like levees, and will serve as a great groundwater replenishment (we all know how groundwater is being depleted everywhere – see this article).

So what needs to be done? Well, for starters, we need a study of the impact to the ecosystem and then plan ecological steps (not just engineering ones) to prevent these catastrophes.