Updated at 6:45 p.m. ET
Water levels in overflowed creeks are slowly starting to decline on the Pine Ridge Reservation.
"What used to be a dry creek is now a swelling, raging river," said Peri Pourier, South Dakota state representative for the district that includes Pine Ridge.
The freshman representative has been coordinating relief efforts for the community, where many residents were cut off by flooded roadways. "There are community and tribe members getting on horseback to reach people and get them supplies," Pourier told NPR.