Nearly five inches of rain fell early morning on June 2 in the Wildcat Creek basin, causing emergency response units to begin blocking off flooding roads. Police officers and firefighters helped evacuate areas of South Manhattan, Garden Way Apartments, Redbud Estates, Highland Ridge Apartments, Village Plaza and Annenberg Park.
Riley County appraisers, who were split into five groups of two, documented the damage in affected areas by taking pictures. Aerial shots were also taken to compare affected areas once the water recedes.
Damage assessments are based on the type of property and the degree of damage to a structure. The goal is to have the information compiled within 24 hours of any incident. All information gathered will be sent to city officials and the Federal Emergency Management Agency to determine if Manhattan residents are eligible for federal aid.
“This year is the worst (flooding in the Wildcat Creek corridor) I’ve ever seen,” said Greg McHenry, Riley County appraiser. “That includes the flood of 1993.”
Riley County Police Department Capt. Kurt Moldrup noted floodwater levels nearly reached that of the predicted 500-year flood. Waters rose so high that trailers floated off of their foundations and tipped over in Redbud Estates.
Many spectators wandered around the flooded areas taking pictures and videos, some stood in awe of the water levels and others tried to take advantage of the rapid current. Local firefighters forced a man back to shore who was kayaking through a flooded area near Fairman. The man launched from his backyard and only paddled half a block before the firefighters confronted him.
“Wildcat Creek started backing up so it had nowhere to go,” McHenry said. “The water came up and moved quickly.”
There have been four major floods in the Wildcat Creek area in the past five years. There is speculation that development west of Manhattan and changes in weather patterns have contributed to the recent flooding.
“The combination of these two things has made a recipe for disaster along Wildcat Creek corridor,” McHenry said.
Shane Swope, Stormwater Engineer for the City of Manhattan, said that due to city ordinance, new developments are not allowed to increase the amount of current runoff. They are required to build detention basins to store runoff water. Manhattan is composed of multiple small stormwater systems, many of which dump right into Wildcat Creek. When the creek levels rise, these microsystems can get backed up, occasionally reversing the direction of water flow.
Robert Ott, Manhattan city engineer, said Leonardville, Kan., is at the top of the watershed and any changes in the watershed area, from development or nature, will affect water levels.
“Only 8 percent of the drainage basin for Wildcat Creek is in Manhattan,” Ott said. “We have no say in what goes on anywhere else in the watershed area.”
These floods affect many people located near the creek in what is known as the floodway fringe. FEMA determines floodway areas, where no structures are allowed to be built because of their high risk to flooding, and floodway fringes, where by FEMA’s rules structures can be built since only larger-scale storms are predicted to affect those areas. In order determine where these floodways and floodway fringes are located, FEMA uses the Rational Method. This calculates the peak discharge of water based on the watershed area, a runoff coefficient and a rainfall intensity factor, the amount of rain expected to fall in a certain time period. Since there has been frequent flooding, Ott requested FEMA reconsider the intensity factor they use in these calculations, but has received no response. Ott said he believes rainfall patterns have changed in this area since the last FEMA report came out in 2005.
Unlike Manhattan, some cities restrict buildings from being built in floodway fringes as well due to frequent flooding. To help predict when there will be flooding issues, Ott helps track water levels in the Kansas River and Wildcat Creek. There is only one gauge along Wildcat Creek and it must be read manually. During the recent flooding, police officers were called to read the numbers on the gauge periodically. At one point the creek rose seven feet within an hour.
“The more accurate measurements we get, the more accurate our predictions are,” Ott said.
The flooding across the Midwest is causing all of the major rivers to rise and all of their tributaries to back up as well. The U.S. Corps of Engineers has put a reduction in release in Tuttle Creek which began Tuesday and will be in effect until mid-August. This reduction only allows Tuttle to release water at a maximum of rate 200-cubic-feet per second. Without additional rain, the lake is still expected to rise a foot every 10-14 days. By mid-August the lake is predicted to be at least 15 feet high.
“Mother nature is like a pipe,” Ott said. “Only so much water can flow in it at one time.”