Field Assessment of Erosion Potential (BEHI)

Bank Erosion is a natural process, advanced by mass wasting, fluvial entrainment, surface Erosion, freeze-thaw movement and ice scour. Channel bank resistance to excessive Erosion is often ranked based on a Rosgen bank Erosion hazard index (BEHI) rating. Characteristics of this BEHI rating include bank height, root depth, root density, bank angle, and surface protection. In this image, the Bankfull flow height is shown by the arrow and Q/B, relative to the bank and its height, angle, root density, soil strata, and particle size. Water table dynamics are also known to influence stability.

BEHI scores are upward or downward adjusted based on bank material and other factors, as denoted on BEHI ranking tables.

• Bank material bedrock - BEHI is ranked very low
• Bank material boulder - BEHI is ranked low
• Bank material is cobble - from BEHI subtract 10 points unless gravel/sand is > 50% of bank
• Bank material is gravel - to BEHI add 10 points
• Stratification of bank material - to BEHI add 5 to 10 points with increasing number and position of layers.

Image modified courtesy of Rosgen