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Update flood risk assessment to reflect reality

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Thanks to skillful local preparations, this week’s flooding did not wash away neighborhoods. But it did wash away some old thinking, especially on the part of some federal officials.

It was back in late 2009 that the Army Corps of Engineers released its assessment of the need for flood protection after the Cedar River’s 31.12-foot crest swamped the heart of Cedar Rapids. Using an outdated statistical model to predict the likelihood of future flooding, the Corps couldn’t justify the cost of building levees and flood walls to protect both banks of the river.

It recommended funding only east bank protection. It figured the risk of flood damage to property over the next 50 years was too low to justify a both-banks protection scheme.

As if that wasn’t bad enough, although approximately $73 million in flood-management funding for the Cedar River project has been authorized by Congress, it has not been funded by the Corps. Eight years after the flood, Cedar Rapids still is waiting for the Corps’ promise to be kept.

Clearly, as this week has demonstrated, major flooding on the Cedar River is no anomaly. It’s a real risk. This time, because the flooding started so far upriver, local leaders had time to put plans for temporary flood barriers into action, saving the city from massive damage. Next time, we may not have enough warning to do so.

At the very least, the Corps should provide its promised funding for the east bank system.

U.S. Reps. Rod Blum, a 1st District Republican, and Dave Loebsack, a Democrat representing the 2nd District, introduced an amendment this week directing the Corps to “expedite” completion of the Cedar Rapids project. On Wednesday, it passed the House.

Sens. Chuck Grassley and Joni Ernst sent a letter to the Corps this week demanding answers about the delay. In that letter, the senators write that they also have asked the Government Accountability Office to review the current method of figuring the costs and benefits of flood risk management projects to determine whether it is adequate and fair to cities such as Cedar Rapids.

We think it’s clearly time for Congress and the Corps to address its methods for assessing the risk, costs and benefits of protecting against potential future disasters. A model based on history does not match our new reality, where heavy rain events are more common and the threat of flooding is greater than in years past.

As Gene Takle, director of the Climate Science Program at Iowa State University, told us this week, “The climate has changed. That’s pretty clear.”

Takle and other researchers have studied flood risks and climate models in Iowa on behalf of the Iowa Department of Transportation, which sought the data to inform bridge design. The 2015 study focused on the Cedar and Skunk River watersheds.

They applied precipitation and streamflow data in the Cedar River Basin to 19 climate models and found a damaging flood in Cedar Rapids is four times more likely now than it was years ago. In other words, what would have been considered a 100-year flood in the 20th century now is a 25-year flood.

Our region is seeing more heavy precipitation events, Takle said. There are more events in the late summer and fall when storms often travel the same northwest-to-southeast path as river watersheds, enhancing flood potential. Humidity levels are rising, as warmer air holds more moisture.

It’s time for the assessment of Cedar Rapids’ flood protection needs to account for this new waterlogged normal. Our risk should be re-evaluated and more resources should be made available. The benefits of permanent protection are clear.

• Comments: (319) 398-8469; editorial@thegazette.com

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