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Additional things to watch out for to avoid future problems:

Steep or vertical banks without vegetation cover

  • Vegetation protects banks from erosion. A steep bank without vegetation is undergoing active erosion and suggests channel movement.
  • Maintaining sturdy vegetation cover – deep-rooted shrubs and trees, not lawns – along the riverbank should always be your first choice in protecting your property from erosion. Lawns are not sufficient to prevent erosion due to their shallow root system.
This bank is bare of vegetation and is being eroded. The grassy area behind the bank is not safe for development as it will soon be threatened with erosion.

Evidence of downslope movement of soil: both along streams and in upland areas

Downslope movement of soil (sloughing) indicates that an area is undergoing active erosion.

Ice jams

Rivers freeze in Montana! Ice jams are sudden floods caused by ice buildup on rivers causing the water to backup into the floodplain. Talk to your neighbors and your Conservation District to learn if your area is prone to ice jams. The dangers of ice jams further reinforce the importance of building at a safe distance away from the riverbank. This website maps ice jams across the state and has more information.

Ice Jam on the Yellowstone River in Montana (Source: NPS)

Outside bends

River bends are where erosion and deposition are actively occurring.  Outside bends – the area of the stream, or river, where erosion happens – are often characterized by steep banks.  These bends tend to move downstream overtime.  Building near an outside bend is hazardous and should be avoided. 

Typical bend on a meandering river (Toni Cardenas, SRCAF Handbook, 2003)
A house built on the bank of this outside bend would have been gone in a few years
This property is being destroyed by the river’s movement toward the outside of a bend

For recommendations on where to build on a property with a river or stream on it, contact a consulting engineer, or your local Conservation District.

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