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River Movement

Rivers move! A healthy river maintains a balance between eroding and depositing sediments. Over time, this process leads to the river channel migrating across the river valley bottom, threatening any structures and developments in its path.

Takeaways

  1. Understand that rivers are dynamic and move over time – an area may look safe for development now but in ten years it may not be
  2. Locate structures outside the channel migration zone
  3. Outside bends of rivers are most vulnerable to erosion

 

 

Learn more about river movement and processes

Thankfully, experts can predict where rivers are likely to move in the next hundred years and have created maps called channel migration zones (CMZs). For the long-term safety of your investment, locate buildings and permanent structures outside the CMZ. Many rivers in Montana, like the Yellowstone and Musselshell, have completed CMZ maps. Contact your local conservation district to obtain CMZs for your area.

Consider CMZs so your house doesn’t end up like this one on the Yellowstone River

Keeping buildings outside the CMZ will reduce the need for costly bank armor. Bank armor harms fisheries and ecological health by interfering with erosion and deposition processes. Bank armor has local benefits, however it prevents the dissipation of energy, intensifying downstream floods and erosion for your neighbors.

Example of channel migration zone map
Selecting a Construction Site
1. Buying Land and Selecting Construction Site
2. Floodplains
3. Septic Systems
4. Potential Hazards
5. Earthquakes
6. Fire
7. River Movement
8. Water Supply
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