It never occurred to Lancaster County Engineer Pam Dingman that she might have to mix Christmas shopping with flooding problems.
But this week Dingman’s office closed a county road because of high water and staff inspected six bridges to make sure the high water hadn’t caused further erosion problems.
Salt Creek got up to about 16 feet at the Roca stream gauge last weekend, when precipitation totaled 1.86 inches at the Lincoln Airport. Flood stage is 19 feet, but water goes over low-lying roads at 14 feet, Dingman said.
So the county had to close portions of Olive Creek Road and Southwest Second Street, she said.
It was definitely a surprise, said Dingman. “I would not have anticipated an event where we would have flooding along with blizzard conditions.”
It wasn’t the amount of rain. However the ground was partially frozen and the water didn’t have an opportunity to soak in, she said.
And one issue created by rain in winter is not covered in any engineering policy manuals, she said.
There is no written procedure for making sure that logs, floating in floodwater, don’t freeze to the road.
That was the situation on Southwest Second Street, where a landowner had apparently cleared some trees and the logs got carried away by high water.
Staff members waited for the water to recede, then quickly cleared the road of cut trees that had floated onto the road.
They also took a look at the county’s worst bridges, termed scour critical, in areas affected by the high water.
The rain event didn’t meet the criteria by the Federal Highway Administration for requiring an inspection based on rainfall. But in this case water levels rose faster than expected because the ground was partially frozen, so it was a high run-off event, Dingman said.
The water washed away material adjacent to the bridges, worsening erosion problems, particularly to bridges in northern Lancaster County, she said.
There was damage to three bridges, including one on Agnew Road between Nebraska 79 and Northwest 56th Street. This bridge is already the worst of the bridges still open, and the county hopes to reconstruct it in the spring.
In Wymore, the heavy rain last weekend may have also broken a major water line, forcing residents to boil water before drinking.
A boil notice is still in effect for users of the Wymore Rural Water System, where nearly 3 inches of rain on Saturday may have caused shifting underground, creating the leak, according to the Lower Big Blue Natural Resources District.
The boil notice stays in effect until no bacteria is present. Testing may not be completed until next week, the NRD said.
Dingman thinks the numerous high-water events in Lancaster County over the past five years are the inevitable result of a changing climate.
Over the past five years, many streams set high-water level marks, sometimes several times, based on U.S. Geological Survey records, she said.