Tuesday, January 26, 2010

You Can't Bury Water

During a discussion at a citizen’s meeting of where possible wetlands were located in South Beach, Oregon, a resident observed that ‘you can't bury water’.  This seemingly simple statement sums up one of the important functions of wetlands.  When large inputs of water enter a watershed during storms, they must go somewhere.  Usually a combination of draining, ponding, and absorption happens.  If the draining stream has big enough banks, then flooding does not occur.  If there is too much water for the stream, then the water floods over the banks and onto adjacent land which forms the floodplain.  This land can be either wetlands where water is welcome and damage is minimal, or it can be filled wetlands with buildings and roads on it and the potential for expensive damage.  

Part of South Beach runs north-south and sits in a basin between beach dunes to the west and forested hills to the east.  Water in the basin can drain out to Yaquina Bay or the Pacific Ocean.  Through the years, filling and development has occurred in the basin and flooding has become worse more frequent in areas that have not been filled.  As fill displaces water, the water is forced to lower land.  This is an example of not being able to bury water.  What happens when you climb into a bath tub and displace water?  The water level goes up and if you are big enough or the water level is close to the top, then you will get a flood on the bathroom floor.  An urban solution to this problem is to build storm sewers, which act like the overflow drain in a bathtub.  
Posted by michael

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