Archive for Thursday, July 17, 2008

Flooding threat still exists

July 17, 2008


"As states assess the damage of the recent floods in the Midwest, they are faced with the same questions that were raised after the flood of 1993: Why were new subdivisions built on floodplains? Why did the levees fail? Why are 'great floods' occurring not every 150 years but every 15?" - New York Times, "Unlearned Lessons from 1993," June 23, 2008

Wet enough for you? Wondering when the summer heat will kick in to dry things out? Relieved that we have lucked out (so far) in escaping this summer's round of Midwestern flooding? Unconcerned because Lawrence is protected by a levee and besides, your property isn't in the floodplain? Think again.

During the 20th century, floods were the No. 1 natural disaster in the United States in terms of the number of lives lost and property damage. This summer, Iowa, Illinois and Missouri experienced serious damage to properties developed in their flood-prone areas, with current estimates of loss ranging from $3 billion to $20 billion. Levees collapsed or were overtopped; at least 25 failures were recorded the week of June 15-21 alone.

Lawrence's levee was constructed from 1967 to 1979 in an effort to protect city investments from flooding. Since that time, it has been observed that levees physically magnify the next flood, making flood levels higher on the new levee as well as areas on the other bank, upstream and downstream. Levees actively promote new development at risk of future flooding.

It's been observed that ever higher, stronger levees lead to higher water levels during floods, with faster moving water building up tremendous force. Even if a levee holds at one location, the water it sends downstream is more powerful and potentially dangerous than before. The town of Gulfport, Ill., was officially removed from the 100-year floodplain after its levee was approved in 1999. The levee failed this June, leaving the town submerged in 10 feet of water.

What happened to our lessons from 1993? Flood buyout dollars provided some opportunity to return flood-prone developments to less risky uses, yet we continued to build in the floodplain by filling it in and impairing it. Loss of wetlands, stream buffers and floodplain storage capacity continued. Elevating structures to build in the floodplain raised the flood levels in that area, changing the statistics and probability measures used to predict flooding, yet we continue to assume that the standard FEMA metrics used in rating flood insurance will somehow protect our property. Residents of North Lawrence have experienced more water problems and minor flooding each year as residential development has proceeded, especially near areas where new houses are built on fill.

We tend not to take serious notice of these problems until the next serious flood cycle comes around. Developers love the flat land of floodplains, enabling the fastest and cheapest possible construction of warehouses and strip malls. For cities, it's easy to regard floodplain as tax base waiting to be developed. However, failure to study the engineering, science and history that support flood control can be extremely costly over the long haul. Coffeyville experienced over $5 million in damages to city services as well as property losses of $16 million in its 2007 flood.

The North Lawrence Drainage Study of 2005 recommended investment of $41 million in drainage structures to support continued development of this floodplain/ flood-prone neighborhood. Very few of the projects on this list have been funded due to financial constraints. Yet serious consideration is being given to extending city utilities northward through the floodplain/flood-prone area to support commercial/ industrial development that would further increase flood risk by adding more impermeable surfaces. It is proposed that the city spend $385,000 for stormwater improvements to support this development.

Since 1973 the Midwest has been hit by four 100-year or 500-year storms.

Meanwhile, climate models predict a 20 percent rainfall increase over the next 30 years, which will result in a 50 percent increase in water to Midwestern rivers.

Continued floodplain development goes against the wisdom acquired through the painful experiences of our flooded Midwestern neighbors. In the words of a Cedar Falls, Iowa, city councilman, "We need as many floodplain restoration projects in the watershed as the number of sandbags used in Iowa."

It's time to stop building for the short term and instead consider the meaning of floodplain. It's an area that floods. We need to respect that it will continue to follow its nature and set our planning and zoning guidelines accordingly.

- Mary Ann Stewart is a civil engineer and a North Lawrence resident.


bearded_gnome 9 years, 8 months ago

and, there has been 0 (zero) comment on this? Mary, you did good here. sounds like we need to push more on the north lawrence drainage study of '05, and levee maintenance, since we do have the levees and homes here now. would you return with another column, you say we need to expand more wetlands (swamps) for outlet mechanisms in case of very high water. good idea, but where do you suggest we put them here in lawrence?swamps breed mosquitos, so aren't we trading one danger for another with the mosquito-born illness?but a very good column here! more should read and ponder...ooops, I guess that's a pun. sorry.

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