The floods as river: the gauge's own table

THE MEASURED LINE, AND WHAT STANDS OUTSIDE IT

The disasters stand in Major Events; here the water's own arithmetic stands: The river at South Bend is a measured river. Its gauge — the U.S. Geological Survey's station 04101225, St. Joseph River at South Bend, read by the National Weather Service as station SBNI3 — stands at the wastewater treatment plant on Riverside Drive, at the city's northern edge, where the whole watershed's water passes a single ruled staff on its way to Michigan. The Weather Service's categories for this gauge, as its page carries them, set the ladder the crests are read against: action stage at 4.5 feet, flood stage at 5.5 feet, moderate flooding at 8 feet, major flooding at 9 feet — the level at which, in the service's own impact language for this point, the river's parks stand almost completely submerged and local streets flood — and the 100-year flood level at 11.1 feet.

The crest record the Weather Service's hydrograph summary states for this gauge is short at the top and is printed whole: before February 2018, the highest water ever measured here was 10.90 feet, and it was reached twice — on 15 March 1982 and on 6 January 1993. In February 2018 the river broke its own record by nearly two feet, cresting at 12.70 feet — a flow the Geological Survey measured at the Niles gauge, just over the state line, at a peak of 25,300 cubic feet per second on 22 February, which the city's flood-study presentation renders as 14.5 billion gallons a day passing through the city, at what the federal flood maps call a 500-year level. The crest's date is carried two ways in the record — the Tribune's anniversary account dates it 21 February, the contemporary report and the Weather Service hydrograph put the peak early on 22 February — and the conflict stands here as it stands, settled as far as it goes, in Major Events, where the flood itself is told as the disaster it was.

Two absences belong in the table as surely as the numbers: The first is the flood of 1908, which this river does not have. The basin's famous 1908 mark belongs to Elkhart's gauge — 26,000 cubic feet per second there on 8 March 1908, still the largest discharge in that gauge's file, against 21,100 in February 2018 — an Elkhart County figure, boundary-printed in Major Events and pointed to here so that no reader imports it into South Bend's table. The second absence is the flood of August 2016, which was not this river's flood at all: the city's own engineers established that the 2016 disaster was a drainage flood, rain overwhelming the city's systems while the river stayed in its banks — it stands in Major Events at its true size, and it is named here only so the crest table is not misread to include it. Before the gauge, the river's violence survives in one documented episode: the great ice gorge of the winter of 1881, when the river's ice destroyed bridges at the bend, preserved in the National Register's East Bank documentation — the pre-instrument flood record of this reach, printed at its size. The basin's context completes the table: at Niles, in February 2018, the same water crested at 17.33 feet, breaking a record of 15.10 feet that had stood since 5 April 1950 — the Weather Service's figures for the next gauge down, printed so the city's 12.70 is read as one point on a rising river, not the whole of it.

Sources:

1. U.S. Geological Survey, station 04101225 (St. Joseph River at South Bend, IN); National Weather Service (IWX), gauge SBNI3 — the gauge's siting at the Riverside Drive wastewater plant (per this record's Major Events, from the Tribune) and its published categories: action 4.5 feet, flood 5.5, moderate 8, major 9, the 100-year level at 11.1 feet and the impact statements.
2. National Weather Service hydrograph record, as settled in this record's Major Events section — the pre-2018 record crest of 10.90 feet reached twice (15 March 1982; 6 January 1993); the February 2018 crest of 12.70 feet; the crest-date conflict (21 vs 22 February) carried from that file; the Geological Survey's peak flow of 25,300 cfs at Niles on 22 February and the city's 14.5-billion-gallons-a-day rendering; the Elkhart gauge's 1908 mark (26,000 cfs, 8 March 1908) boundary-printed as Elkhart's; the August 2016 flood established as a drainage flood by the city's engineers.
3. National Weather Service (IWX), February 2018 flood summary — the Niles crest of 17.33 feet against the previous record of 15.10 feet (5 April 1950).
4. National Register documentation for the East Bank / Howard Park area, as carried in this record's Industrial Revolution section — the great ice gorge of 1881 destroying bridges at the bend.