The Great Flood After 100 Years

The Dayton Daily News features a series remembering the Great Dayton Flood of 1913, and its impact on the region:

One hundred years ago today, Daytonians had no idea that the winds from a monster Easter Sunday tornado in Omaha, Neb., and the Gulf Coast states would soon be wreaking havoc with their own city. It already had been an unusually wet winter, saturating the ground and setting the stage for disaster.
On March 21 — Good Friday — the first storm hit, with 45 mph wind gusts that knocked out telegraph lines. The rains began in earnest on March 23, Easter Sunday, pounding the Miami Valley with eight to 11 inches of rain over a five-day period. The runoff found its way to the Great Miami River, at the pinch point where four rivers — including the Mad River, the Stillwater River and the Wolf Creek — meet near downtown Dayton.
In 1913, Dayton was a bustling city of 117,000 residents, the 43rd largest city in the nation. It had endured 10 major floods, rebuilding the earthen levees each time, and seemed to regard occasional flooding as the price of prosperity. But this time, the levees couldn’t withstand the sheer volume of water from the Great Miami and its tributaries — 250,000 cubic feet of water per second through a channel with a capacity for 25,000 cubic feet. “This flood was so large that 90 percent of the total volume of water had to flow through Dayton’s city streets,” explained Julia-Dian Reed of the National Weather Service in Wilmington.
Sirens, alarms and church bells began sounding during the early morning hours on Tuesday, March 25, but many Daytonians failed to take the warnings seriously, until it was almost too late. Fred Noble brushed off his wife Wealthie’s concerns about the safety of their family of 11 children, who lived at 142 W. Columbia St., very close to the levee. “It gets this way every year; we’ll be OK,” he assured her.
By early Tuesday morning, the river level had risen to 11.6 feet, raising deepening concern and attracting gawkers to the bridges and riverbanks, unaware that three of the city’s levees had come close to failing. Curiosity turned to terror around 8 a.m. when the main levee broke at Webster Street and a 10- to 20-foot wall of water swept through St. Clair, Jefferson, Main and Ludlow streets. Thousands ran or swam for higher ground.

The flood brought about the creation of the Miami Conservancy District, which designed and constructed a series of levees and flood control reservoirs to protect the region from a flood 40% larger than the 1913 flood:

The Official Plan Flood (OPF) is the flood on which all Miami Conservancy District channels, levees and dams are designed. The March 1913 flood was, and remains, the flood of record for the Great Miami River Watershed. 
The rain fell on ground already saturated from the melting of ice and snow of a hard winter, resulting in a runoff rate of 90 percent.

After an exhaustive investigation of precipitation and flooding data, Arthur Morgan, the system’s engineer, felt that a flood protection system that could handle the 1913 flood, plus 40 percent additional runoff, should protect the cities from all flooding by the Great Miami River.