The river in flood: the great flood, the later pair, and the fight

MARCH 1982 — FEBRUARY 2018 · CREST FIGURES AS CONFORMED IN THE RIVER RECORD

The great flood, March 1982: The documented great flood of this reach before the record flood was a snowmelt flood: the rapid melting of a snowpack holding two to six inches of water, with moderate rain, flooded the whole northern tier of Indiana, and the U.S. Geological Survey's report on the flood assigns the St. Joseph River's flooding a recurrence interval of about fifty years. The crest at the South Bend gauge, four miles below the Mishawaka dam, stood at 10.9 feet — the record for that gauge until 2018.

The later pair, with the argument about the numbers printed whole: In August 2016 a rain flood sent five and a half billion gallons a day through the South Bend reach, on the county's accounting. In February 2018 came the fullest documented flood in the record: nearly thirty inches of snow on the ground by 17 February, then record February rain — more than eight inches for the month, 3.75 inches on 20 February alone — as the temperature rose above sixty and the snowpack let go. The river crested at South Bend at a historic 12.7 feet on 22 February, and at Niles at 17.33 feet, more than two feet above the standing record of 15.10 feet set 5 April 1950. The numbers around that crest are argued in the record, and the argument prints with them. The crest is also carried as 12 feet 7 inches in South Bend's council record — the same water in the other notation, a tenth of a foot under the gauge figure. The flood's rarity is carried at two strengths that do not reconcile: against the Geological Survey's roughly fifty-year recurrence for the 1982 flood stands the claim, reported in South Bend's council discussion of March 2018 from Notre Dame data for 1931–2017, that the February 2018 flood stood at a 2,500-year level. And the human count divides by geography, not by error: the county emergency figures given out that March counted about 700 homes affected in St. Joseph County, 65 of them with major damage, while the Tribune's one-year retrospective counts about 2,000 homes damaged across the three-county Michiana region and millions in costs to local governments. No figure here has been averaged or chosen between. One absence belongs to the series: no Mishawaka account of the famous March 1913 flood was reached — that flood's documented record belongs to the Wabash and Maumee valleys, and the St. Joseph at Mishawaka has no 1913 crest in the record reached.

The flood-fight, February 2018: Mishawaka's fight was fought at Merrifield Park and at the treatment plant, and its outcome was designed a century of floods in advance. The water, in the city engineer's account a year later, did as expected: it hit the known floodplain, where the city had built parks rather than buildings. Kamm Island, Monkey Island and Beutter Park went under, the Riverwalk drowned under the Main Street bridge, and parts of the Eberhart-Petro golf course flooded, with no long-term issues left behind. The fight itself was at Castle Manor in Merrifield Park, where city crews rushed sandbags and a pump to the newly renovated building and averted damage to the park's roughly three-million-dollar makeover. Through the week of the flood the wastewater treatment plant kept operating at three times its normal flow — the longest sustained period of peak flows Mishawaka Utilities had ever treated — and no sanitary sewer pipe collapsed, which the city credits to a decade of annual line rehabilitation. The flood's one structural wound was a road: a washed-out stretch of state-owned Lincolnway just west of Logan Street, where erosion undercut half a lane and the Indiana Department of Transportation kept a lane closed from February until September, rebuilding the embankment with sheet metal and concrete. By spring, volunteers had cleaned the mud out of Beutter Park. The flood made no policy change in Mishawaka, the engineer said — the parks-as-floodplain policy was the change, made long before, and February 2018 was its vindication.

Sources:

1. The events and parks-and-river records of this build — U.S. Geological Survey, Floods of March 1982, Indiana, Michigan, and Ohio (WRIR 83-4201) for the fifty-year recurrence and the 10.9-foot crest; the February 2018 figures (snow, rain, the 12.7-foot crest of 22 February; Niles 17.33 feet against 15.10 feet on 5 April 1950) from the City of South Bend's flood-study testimony and the National Weather Service; the August 2016 flow on the county's accounting; the March 1913 absence printed as an absence.
2. City of South Bend council discussion, March 2018, as carried in the city's flood record — the crest stated as 12 feet 7 inches, and the Notre Dame 1931–2017 data reported as putting the February 2018 flood at a 2,500-year level.
3. South Bend Tribune, February 2019, the one-year flood retrospective (read in its syndicated form) — City Engineer Chris Jamrose on the floodplain parks, the Castle Manor sandbags and pump and the $3 million Merrifield makeover saved, the treatment plant's three-times-normal flow, the sewer record, the Lincolnway washout and the September INDOT repair, the volunteer cleanup of Beutter Park, and the region-wide count of about 2,000 homes damaged; the county emergency figures of March 2018 (about 700 homes affected in St. Joseph County, 65 with major damage) as carried in the events record.