Flooding from river overflow and flash flooding from heavy rainfall dominates Oglala Lakota County. Over the last 30 years, the NOAA Storm Events Database has recorded 18 flood events and 9 flash flood events.
Recent history demonstrates this recurring risk. In May 2023, a prolonged multi-day rain event dropped three to five inches of rain—with nearly four inches falling within six hours—causing flooding and flash flooding across the Cheyenne and White River basins as water flowed into larger rivers. Later, in August 2022, heavy rain from thunderstorms produced localized flash flooding in Porcupine, where water ran over roads.
Properties situated near the Cheyenne and White River basins, as well as homes located near low-lying areas and roads susceptible to rapid runoff, should pay the most attention to local flood risks.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
8 NOAA storm reports from Oglala Lakota County describe what happened, in the words of the forecasters who covered it. Read the South Dakota flood stories →
27 since 1996: 9 flash floods and 18 river or area floods.
| Event | Date | Damage |
|---|---|---|
| Flood | May 12, 2023 | — |
| Flood | May 11, 2023 | — |
| Flash Flood | May 11, 2023 | — |
| Flash Flood | Aug 24, 2022 | — |
| Flash Flood | Jul 29, 2020 | — |
| Flood | May 28, 2019 | — |
| Flood | May 26, 2019 | — |
| Flood | May 21, 2019 | $100,000 |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flood · May 12, 2023. A prolonged rain event over several days led to flooding and flash flooding over the Cheyenne and White River basins. Three to five inches of rain fell, with some locations receiving nearly four inches of rain within six hours on the evening of May 11. As the water flowed into larger rivers, minor flooding was observed.
Flood · May 11, 2023. A prolonged rain event over several days led to flooding and flash flooding over the Cheyenne and White River basins. Three to five inches of rain fell, with some locations receiving nearly four inches of rain within six hours on the evening of May 11. As the water flowed into larger rivers, minor flooding was observed.
Flash Flood · May 11, 2023. A prolonged rain event over several days led to flooding and flash flooding over the Cheyenne and White River basins. Three to five inches of rain fell, with some locations receiving nearly four inches of rain within six hours on the evening of May 11. As the water flowed into larger rivers, minor flooding was observed.
Flash Flood · Aug 24, 2022. A supercell thunderstorm developed over the southern Black Hills and tracked southeast, weakening on the adjacent plains. The storm produced large hail and heavy rain over the area. Other strong thunderstorms produced heavy rain and localized flash flooding over far southwestern South Dakota. Rain amounts of three to four inches were estimated in some areas. In Oglala Lakota County, flash flooding quickly occurred…
National Weather Service narratives, lightly trimmed. Source: NOAA Storm Events Database.
Every colour on the map above is a place on this drawing: where the ground sits relative to the flood FEMA plans for.
If a building in Oglala Lakota County is in a high-risk zone (A or V) and its mortgage comes from a federally regulated or insured lender, or is federally backed, flood insurance is required.
Outside those zones it is optional, and often worth having: from 2014 to 2024 nearly one-third of NFIP claims came from outside the high-risk Special Flood Hazard Area. Since Risk Rating 2.0, NFIP premiums are set for each building, so the only reliable price is a quote: FloodSmart.gov or a local agent.