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Thu July 3, 2008
Comparing Texas levy systems to Midwest
By Scott Harvey
As Midwesterners begin to assess the damage following recent flooding, area residents may be wondering how safe our existed flood systems are.
Fred Jensen is a Hydraulics Engineer with the Forth Worth District Army Corps of Engineers. Jensen says Texas uses more lake systems, as opposed to river-based, and has an abundance of flood control reservoirs to aid in prevention.
Just in the Forth Worth District alone there are 25 reservoirs that are federally funded, which includes Cooper Lake in Northeast Texas. Not near as many federally funded reservoirs exist in the Midwest.
The difference between a federally funded and non-federally funded levy system, according to Jensen, are the strict guidelines government based systems have to adhere by in order to receive funding.
For example, they are not allowed to grow trees on levies. Jensen says that was a major reason for several levy breaches in the Great Flood of 1993 that, in some cases, destroyed even more property in the Midwest than last month.
Because these types of levies are not funded properly, they can be more susceptible to breaking due an inability to maintain, weakness or and/or poor construction.
One reason some federal levy systems do break, as evident along the Mississippi River both in 1993 and this year, was because there was so much water in the system it had no where to go.
''Pretend your bathtub walls are made of dirt, after awhile walls get so saturated with water they can't hold any longer,'' says Jensen.
The good news for North Central and Northeast Texans comes in a couple forms. First, local federally funded levy systems are constantly under the microscope, having to be built a certain way and inspected before more funds are made available.
Second, Texas doesn't tend to receive near as much rain as the Midwest; therefore those levies are not tested nor weakened to the same degree, which keeps the system strong and not as susceptible to break.
An issue the Forth Worth District doesn't have to deal with is a flood control system that spans several states. Not all states, according to Jensen, abide by the same flood control tactics.
For example, Rock Island, Illinois escaped flooding in 1993 because they had built strong levies and reinforced them with a concrete flood wall on top. However, on the other side of the river, in Davenport, Iowa, there was little done to prevent flood waters from submerging portions of town.
The same is evident down river, when high levies and walls in one town may prevent flooding, but in turn raise the water level because it can't spill over, possibly hurting communities to the south that don't have as strong a flood prevention system.
Jensen says the last major line of flooding to hit Dallas was in the early 1990's. During that time, Dallas floodways had major flooding, but no levies were breached.
All in all, it depends on where you live and the amount of rainfall your area receives each year. It also depends on if you have the resources to build and maintain strong flood control systems that will protect you when needed.