River‐bed Sedimentation Caused by Off‐road Vehicles at River Fords in the Victorian Highlands, Australia¹

This study investigates some of the effects occurring at recreational off‐road vehicle (ORV) crossings on two rivers in eastern Victoria, where many road crossings occur at low‐level fords. Further, it provides a method whereby the amount of sediment redeposited downstream of a ford can be measured. Attention is drawn to the fact that sediment is contributed to the river by five major processes: the creation of wheel ruts and concentration of surface runoff, the existence of tracks and exposed surfaces, the compaction and subsequent reduction in the infiltration rate of soils leading to increased surface runoff, backwash from the vehicle, and undercutting of banks by bow wave action. The last two of these processes have not been reported previously. Sediment collection experiments in two Victorian upland rivers indicate a mean deposition rate at the stream bed of approximately 1000 g m −2 over a period of 30 days.