Rivers in Montana are wild and do not always stay within their banks. During the spring melt or after intense rains Montana’s rivers periodically spill over their banks into the adjacent land, or the floodplain. To avoid getting wet, locate buildings and permanent structures well outside the 100-year floodplain, which is the land that has a 1% change of flooding in any given year. Learn about flood insurance.
- Before you build, find your 100-year floodplain and check local regulations
- Build outside the floodplain to protect your investments from flooding
- A common misconception is that a 100-year flood happens every 100 years. 100-year floods have a 1-in-100 chance of happening in any given year.
How can I find out where the floodplain is?
- FEMA provides official floodplain maps
- Your city or county planning department may have floodplains maps and recommendations
- If you need help finding floodplain maps in your area, talk to your local conservation district
Example of 100-year floodplain along the Yellowstone River.
To avoid risk of flooding, build outside the floodplain.
Choosing to build outside the floodplain will reduce the need to build expensive and environmentally damaging flood control structures. While it may be inconvenient for us, flooding is an important mechanism for maintaining river health. Floodplains spread and store water during high flows, reducing damaging erosion and further flooding downstream. Floodwaters exchange nutrients, sediments, and organisms between the channel and the floodplain, creating unique habitats that are critical for the survival and reproduction of many species.