De-Mystifying 100 Year Flooding
Maia Wijnberg ’26
Katy Su ’28
If you have ever read about flooding, you have probably seen the term “100-Year Flood.” The real question is: what does that even mean? The common misconception is that a 100-year flood refers to a weather event that occurs once every 100 years, but in reality, the term describes the flood’s recurrence interval (U.S. Geological Survey, 2018). Essentially, the recurrence interval is the probability of a flood of a given magnitude occurring in a single year. In other words, a 100-year flood is a flood that has a 1 in 100 or 1% chance of occurring. This metric develops according to the probability that the weather event will be equaled or exceeded in a given year. For example, if there is a 1 in 50 chance of a region getting five inches of water in 24 hours, then a rainfall total of 5in. has a 50-year recurrence interval. Therefore, the 100-year or 50-year floodplain is the region that has a 1% or 2% chance of flooding in a single rainfall event.
So why does Loomis care about the floodplain? Well, Loomis Chaffee sits on the confluence of the Connecticut and Farmington rivers, which also places us heavily in the risk zones of flooding events. The 100-year floodplain runs over all entrances to campus, meaning that if the event were to occur, students and faculty would need to evacuate until the water recedes. In fact, this was the reality for the community in the spring of 1936 and 1984 (Loomis Chaffee Archives. Students left campus, some even by boat, and put up in hotels in Hartford or taken in by local Windsor families while campus remained an island. These great floods certainly left their mark on the school, between the massive amounts of rebuilding and cleaning up after the water damage to the marker down by Physical Plant, memorializing just how high the water climbed. All in all, 100-year floods are just another characteristic that makes life on the Island so special.
References:
Loomis Chaffee Archives. (n.d.). The Flood of 1936. Loomischaffee.org. Retrieved February 28, 2026, from https://www.loomischaffee.org/archives/post/~board/archives/post/the-flood-of-1936
U.S. Geological Survey. (2018, June 11). The 100-Year Flood. USGS. https://www.usgs.gov/water-science-school/science/100-year-flood
