RIVER‐BED SEDIMENTATION CAUSED BY OFF‐ROAD VEHICLES AT RIVER FORDS IN THE VICTORIAN HIGHLANDS, AUSTRALIA¹

Abstract

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 runof! 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 m2 over a period of 30 days. (KEY TERMS: off-road vehicle; sedimentation; river ford; environment; Victorian Highlands.)

The Selwyn River of New Zealand: a benchmark system for alluvial plain rivers

“…Riffles are the favoured ORV fords in the Selwyn River, and wheel ruts and abraded rock surfaces have been observed at many riffles. ORV use can also lead to bed material compaction and fine sediment deposition downstream of fords (Brown, 1994). Like gravel extraction, ORV use disturbs the surface armour of channels, increasing bed-material mobility.…”

Ecohydrological disturbances associated with roads: Current knowledge, research needs, and management concerns with reference to the tropics

“…The occurrence and types of benthic invertebrates specific to a river are in part controlled by the grain size of a riverbed, with cobble or pebble substrates supporting both greater diversity and abundance than sand­ or silt­dominated substrates (Angradi, ; Hynes, ; Minshall, ; Vouri & Joensuu, ). Fine sediment entering streams increases turbidity and/or suspended solid concentrations (Grayson et al, ), disrupting stream ecosystems by inhibiting photosynthesis and changing channel morphology and stability (Beschta, ; Brown, ; Eaglin & Hubert, ; Reid & Dunne, ).…”

“…Many studies investigating road run‐off in temperate areas have focused on de‐icing salts and heavy metals. The primary de‐icing agent, sodium chloride (NaCl), is toxic to many species of plants, fish, and other aquatic organisms (Amrhein, Strong, & Mosher, ; Brown, ). Calcium chloride (CaCl), commonly used to decrease road dust in the tropics, may also inhibit amphibian movement (DeMaynadier & Hunter, ).…”

“…This example demonstrates why road placement is crucial in steep tropical watersheds that drain to sensitive ecosystems. (Unpublished data from the Browning et al, 2016 study) disrupting stream ecosystems by inhibiting photosynthesis and changing channel morphology and stability (Beschta, 1978;Brown, 1994;Eaglin & Hubert, 1993;Reid & Dunne, 1984).…”

“…In addition to fine sediment, various other pollutants from road run-off can affect stream ecosystems negatively (Brown, 1994;Gilson, Malivia, & Chareneau, 1994;Lamont & Blyth, 1995;Yousef, Wanielista, Harper, & Skene, 1983;Yousef, Wanielista, & Harper, 1985). Depending on the location, rural versus urban, as well as the land use (e.g., agriculture and mining), road run-off may include a range of pollutants such as fertilizers, pesticides, herbicides, solutes, heavy metals, plastics, polycyclic aromatic hydrocarbons, mineral oil hydrocarbons, pharmaceutical contaminants, and soluble salts (Froehner et al, 2012;Göbel, Dierkes, & Coldewey, 2007;Hussain, Rahman, Prakash, & Hoque, 2015;Wang, Zhang, Wu, & Wang, 2017) Many studies investigating road run-off in temperate areas have focused on de-icing salts and heavy metals.…”