DIVERSION POTENTIAL AT ROAD-STREAM CROSSINGS

Rarely can roads be designed and built that have no negative impacts on streams. Roads modify natural drainage patterns and can increase hillslope erosion and downstream sedimentation. This paper examines the flowpath of overflowing water and associated load. Stream crossings frequently have the potential to divert streams from their channel if the capacity of the crossing structure is exceeded. Road-stream crossings with diversion potential typically pose much greater overall risks than those without diversion potential. Designing roads to avoid diversion potential is straightforward, and remediating existing crossings to correct diversion potential is usually inexpensive. This paper discusses the physical effects of diversion potential, and provides design considerations for remediation of existing crossings that have diversion potential.