Flooding

The news recently has been reporting about flooding around both the Mississippi and the Richelieu rivers. Both remind me of 18 years ago when our graduate design class went to the aftermath of the flooding along the Illinois river in the fall of 1993 in order to do damage assessments for FEMA. It was tragic because these types of events tend to hurt the most vulnerable people in society. Since flood plains carry the risk of occasional floods, the land is cheaper and attracts people who can’t afford other locations. So it was hard to enter the homes back then and see black mold already forming and thick up to 4 feet above the floor. The home would likely have to be demolished.

But why is this happening? Why are there reports that these are the highest floods in years? A case can be made that global warming ironically plays some part due to increased snowfalls. But just as with the Great Flood of 1993, most of it has to do with development.

First, when we develop land we tend to pave it over for parking lots, or roads, or just to avoid water from collecting. So when it rains, it is carried to the local storm sewer. Before the land had been developed, the water had a chance to be absorbed before it became saturated and runoff occurred. The sustainability movement for the built environment has become sensitive to this and encourages reducing or eliminating rainwater runoff.

The second problem that development is creating is that water is channeled to rivers and once inside the rivers, is usually channeled to either the next lake, river, or the ocean. It used to be that natural occurring floods would overflow their banks adding nutrients to the river basin. It replenished, was filter by, was absorbed by wetlands. It also created the fertile farmland now bordering the rivers. But now that development has created defined barriers with levees or concrete riverbanks, the water has nowhere to go but up. Since the amount of water entering the system is ever increasing due to the lack of absorption upstream, even more water enters the system and water just keeps getting higher until either a levee breaks or they hold and are built even higher for the next one.

The irony is that the levees are holding back from the bordering farmland the nutrients that made them so desirable. The summer after the flood in 1993, I returned to see the area. The farmland that had been flooded after the levee broke was so incredibly green that it makes you wonder why the rivers are not allowed to flood on a regular basis (with the proper precautions).

Another way to reduce the impact of floods is to reintroduce wetlands. Development and property ownership has destroyed so many natural areas. These areas are seen as a nuisance and must be built over or harnessed. Without regard to the natural environment, this attitude passes the buck to the next guy downstream or even the next generation.

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~ by Frank on May 10, 2011.

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