08-20-18 Health and Public Saftey & Utilities

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0 CITY OF SOUTH BEND I OFFICE OF THE CLERK you look at this map (available in the City Clerk's Office), it shows the snowfall prior to when it started to warm up. If you look at the blue, which is indicating anywhere from eight(8)to sixteen (16) inches of snow depth, you can see that it's over the entire St. Joe Watershed Basin, and that was critical. He continued, Then we had precipitation. Temperatures warmed up and we had over eight (8) inches of rain which fell in February, which was an all-time record for the month. The previous record was five (5) inches. Most of that occurred in three (3) days. On February 20th, in one (1) day, we had three point seven five (3.75) inches of rain, which was the new single-season day record. Here we are with record events in snowfall and rainfall, along with temperatures warming up while the ground is saturated. These made for a perfect event for flooding. He described a graph (referencing a slide of a presentation which is available in the City Clerk's Office) which depicted the amount of snowfall, the maximum and minimum temperatures, along with the rainfall. He stated, Storms of this magnitude, and all of these different things falling into place, do not typically occur in any given year. This was a very extreme event, and it is not something you see very often. If you look at it in terms of river level, this was a five hundred (500)year event. If you look at it in terms of flow,we were well beyond a five hundred(500)year event. Mr. Metters, (referencing a slide in the presentation), pointed out that the gauges in other surrounding communities were at or near the record levels for those sites. He stated, If you were watching the storm track of the rain,this storm tracked south to northeast over the entire watershed, which caused a widespread event. South Bend reached the flood record and exceeded it. River levels were point two percent (0.2%) annual chance levels for the five hundred (500) year flood. FEMA uses a percent chance that you are going to get this type of flood. This was about a 2500 year flood. He went on, In August 2016, we had another event. I want to show how different storm events can happen and affect different areas. This was a very tense, low duration event. We had eight point five (8.5)inches of rain fall over a nineteen(19)hour period. This storm event was not even within the top twenty-five (25) historic readings on the South Bend gauge. It was just because of where the rain fell, how it fell, and what was going on within the rest of the watershed. The flow in the river during the 2016 event was about 9,000 cubic feet per second. Storms can be very hard to compare, so you can't just look at the numbers. He continued, The first (1St) thing we did was develop a questionnaire that was available online and was distributed door to door, and we ended up getting back a lot of good information. We asked questions ranging from if people flooded in 2018, if they flooded in 2016, if they flooded during any other events and how often, what was the source of the flooding, if they had backflow prevention devices, and we also asked them to provide comments. Those two hundred (200) responses helped us gain information we couldn't get from the data. He stated, A lot of analysis was done on the areas they were evaluating. In the North Shore Triangle, seven percent (7%) flooded in 2016, nineteen percent (19%) in 2018, and sixty-one percent (61%) flooded in both. Another question asked was whether residents' downspouts have been disconnected. Out of the people surveyed,Keller Park had sixty-six percent(66%)that were, EXCELLENCE ACCOUNTABILITY I INNOVATION I INCLUSION I EMPOWERMENT 455 County-City Building 227W Jefferson Bvld South Bend,Indiana 46601',p 574.235.9221 f574.235.9173 TTD574.235.5567 www.southbendin.gov 4