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Most of the major gully erosion along the floodplains of Eight Mile Creek near Oriners is
created and accelerated by vehicle roads and tracks. When primate tracks have light traffic,
are covered well by grass, and are driven by cautious and attentive drivers, they can be quite
stable and produce less sediment than larger more developed dirt roads. However when
small tracks are driven during wetter periods by aggressive drivers and/or during periods of
low vegetation cover after fires, they can begin to erode in sensitive areas such as creek
crossings, inclines, boggy areas, and sandy areas. The mechanical breakdown of alluvial
soils into “bull-dust” in the dry season can also initiate gullying when this material is easily
washed away in the wet season. Often initially small road disturbances can concentrate
overbank floodwater and through positive feedbacks then erode into large gullies. Roads
parallel to the flood flow in alluvial valleys (Figure 57) are very prone to linear gullying and
can even facilitate the creation of new anabranches (Figure 73a). Whereas road crossings
through creeks can accelerate local water delivery and the creation of bank gullies (Figure
88).
Examples of initially small road disturbances creating large linear gullies into alluvium are
widespread along Eight Mile Creek, such as along the western access road to Oriners
(Figure 73a), the eastern access road (Figure 73bcd), or the airplane landing strip (Figure
73ef). Severe road damage at the upstream end of Oriners Lagoon has reduced the local
base level and triggered massive gully erosion into shallow drainage ways (dambos)
upstream (Figure 72). Most of these gullies have formed in the last 20 years, but were a
consequence of earlier settlement patterns and road placement (Figure 38). Small scale
regular maintenance and seasonal touch-up of primate tracks with small equipment like a
tractor is key to longevity, and could have stopped many of these gullies issues before they
got to this stage. In contrast, careless large-scale machine work using bulldozers and
graders can actually accelerate gully erosion by scouring into highly erodible soils, removing
protective grass cover and concentrating larger volumes of water. The fragile nature of the
Oriners landscape means that major road works need to follow strict Best Management
Practices, consulting local knowledge holders, building up road prisms with imported
material, and conducting regular maintenance.
The newly cleared bypass road around Oriners homestead (circa 2010; Figure 74ab) and
plans for major upgrades of the road through Oriners Station (circa 2012/2013) could
improve access and road drivability, but also could have significant unintended
consequences (e.g., erosion, sedimentation, weed spread). They could accelerate soil and
gully erosion and sediment delivery to major residential and cultural sites such as Oriners
and Jewfish Lagoons. Examples already exist of gullying into swampy valleys and drainage
ways (dambos) from excess water delivery (Figure 74cd), as these valleys are highly prone
to disturbance. It is likely that the new road construction will increase the water and sediment
delivery to these dambo valleys via road runoff, which could destabilize them and lead to
further gully incision (Figure 74ef). It is essential that roads are properly designed to match
the topographic and erodible soils. Water runoff and sediment delivery must be carefully
mitigated through the implementation of abundant Best Management Practices (BMPs) such
as frequently spaced and abundant diversion drains (i.e., < 20m spacing onto safe dispersal
sites). Unfortunately, existing completed road designs in the area are far from adequate to
reduce or eliminate excess water and sediment delivery to aquatic systems (Figure 74f).
Working Knowledge at Oriners Station, Cape York
167