South Dakota: Overview

Everything in the main manual and the skill guides applies in South Dakota exactly as written. What’s different here is the specific hazard profile and the state, local, and legal context around it. This page is the starting point; the other three pages under South Dakota go deeper on laws, local resources, and the data behind the risks named here.

The 1972 Black Hills flood: rainfall plus a dam failure

On the night of June 9-10, 1972, nearly 15 inches of rain fell in about six hours near Nemo in the Black Hills, overwhelming Rapid Creek and other waterways. Canyon Lake Dam, clogged with debris from the flooding, failed outright late that evening, sending a wall of water through Rapid City. The combination, extreme rainfall on top of a dam failure, made this the most detrimental flood in South Dakota’s history and one of the deadliest floods in U.S. history, killing 238 people. See the Risks page for the full data.

The 2015 Delmont tornado: a small town hit directly

On May 10, 2015, an EF2 tornado tracked more than 16 miles through southeastern South Dakota and struck the small town of Delmont directly, severely damaging or destroying 44 houses and leaving the entire town without power and water for two days. It’s a useful modern case study precisely because of its scale: a single tornado can disable an entire small town’s basic utilities for days even without producing a large death toll. See the Risks page for the full data.

What this means for how you use the rest of this manual

The manual’s Tier structure and the skill guides apply without modification. What’s different in South Dakota: this manual’s guidance about not relying on a single point of infrastructure failure, like a dam, applies directly given Rapid City’s history, and Delmont’s two-day utility outage after a single tornado is a reminder that a small town’s entire infrastructure can be knocked out at once in a way a larger city’s redundancy might partially absorb.

Sources

• 1972 Black Hills flood data: Wikipedia; National Weather Service
• 2015 Delmont tornado data: South Dakota Magazine; South Dakota Response