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A total of 4.41 inches of rain fell in the city from the storms, according to a rain gauge at the new wastewater treatment plant.
Of that amount, about 3.5 inches fell in a 90-minute period, according to National Weather Service data.
"The bulk of the rain came in a short time and using data from the National Weather Service, that storm almost was considered as a 100-year flood event. So it wasn't just another storm. It was an extremely intense storm," said City Engineer Dan Boyce.
City Administrator Jim Briggs said he was approached this past week by consulting firms looking to investigate the situation.
Dr. Charles Morris and Dr. Paul Munger, of Morris and Munger Engineers, LLC, a consulting firm based in Rolla, attended Monday's meeting to talk about services they could offer to the city.
Morris said his firm specializes in stormwater management and stream stability and restoration.
"We can collect data and look at where there are erosion problems along streams, look at buffer areas that keep development away, and with any changes we do make to streams, we try to keep them as natural as possible," he said.
Morris said his company can complete studies to show communities how to mitigate floods and expand the capacity of streams through stormwater master plans. The firm also can update the city's Federal Emergency Management Agency (FEMA) floodplain maps.
Washington's FEMA maps have not been updated in years, it was noted. In 1978, the city commissioned a flood plan study, which was adopted in 1980.
An independent study prepared after a flash flood in 2000 placed the area of the Dawn Valley Subdivision in a floodplain, Briggs noted. The subdivision also was impacted by the Sept. 20 storms.
The city did not adopt the standards from the 2000 study because of strong opposition from property owners.
While Councilman Tim Overschmidt said some of the older studies, including the 2000 study, are still accurate, Briggs said "those studies don't go into detail like the one being proposed."
Morris noted that cities should look at an overall view of their flood issues.
"We have programs that look at stream stability, but we also have programs to examine streams as cities develop because that will change things," Morris said.
Councilman Guy Midkiff said he liked the holistic approach.
"We also can prioritize the areas to show where you can best spend your money," Morris added.
Depending on what the city wants, a plan could cost anywhere between $20,000 and $50,000, Morris said.
Briggs said money for a study could come from the city's stormwater fund.
"Any solution is going to be very, very expensive," Briggs noted. "So, maybe thre is some money that the council wants to set aside in the capital improvement sales tax fund for work on major drainage basins."
Midkiff warned council members of the effects of updating the city's floodplain maps.
"We need to make sure the public understands that if a consultant comes in and modifies the plan, it's going to have a phenomenal impact on development here in town. It will bring changes in a big way."
Briggs agreed, noting that updates may cause some property owners to get flood insurance and may affect what can be developed in those places.
