We are just one day shy of the 45 year anniversary of one of the worst floods in United States history. Black Hills FOX meteorologist Jon Wilson has more on how the weather came together to create such a catastrophe.
Susan Sanders from the National Weather Service, Rapid City says, "There was incredibly humid air over eastern South Dakota, and the east winds brought all that moisture over to Rapid City and the Black Hills, and when that air hit the Black Hills, it rose and the clouds started forming along the eastern slopes."
The heavy rain eventually started, and it didn't stop for hours.
Sanders says, "What was kind of unusual, especially for this area because we know that there's always wind, there wasn't any wind above the Black Hills and so the thunderstorms just grew and developed and they didn't move off."
The torrential rains continued through the evening hours of June 9th, leaving heavy rainfall totals across the eastern slopes of the Black Hills.
Sanders says, "There were estimates, because we didn't have a lot of rain gauges of up to 15 inches around Nemo and Johnson Siding, and then down by Pactola, east of Pactola."
15 inches of precipitation in just a matter of hours in a place that normally gets about eighteen inches of precipitation throughout the entire course of a year. That left the water with no place to go.
Sanders says, "So all that water just came rushing downstream into Rapid City. The change in elevation made it really fast-moving."
The banks spilled out of Rapid Creek, inundating surrounding homes and businesses. 238 people lost their lives, and over 1300 homes and 5000 vehicles were destroyed. That tragedy lead to advancement.
Sanders says, "We've put in rain gauges and river stream gauges all along Rapid Creek and its tributaries, so we can see not only how much rain has fallen into those streams, but how fast those streams are rising."
The city instituted a flood-management plan shortly after the flood, creating a greenway along the creek to protect citizens if this rare event ever were to ever occur again. This flood is not only memorable for Rapid City, but to this date, it still ranks as one of the worst in United States history.
There have been other floods that have been caused by heavy rain and Rapid snow melt, dam breaks like Johnston, Pennsylvania, or hurricane rain, but this is actually as far as a single thunderstorm, the deadliest flood in the United States.