Future Research Priorities
Natural Vegetation Recovery Within and Above Alluvial Gullies
- The natural vegetation recovery potential within alluvial gullies and vegetation influences on reducing alluvial gully erosion are major topics for long-term research. Short-term cattle exclusion experiments cannot answer critical long-term recovery unknowns. The installation of small cattle exclusion experiments and direct revegetation conducted in this study are significant steps towards this research; however funding is needed for their continuation and expansion to larger land management units.
- ‘Soil conservation areas’ in high risk areas for alluvial gully erosion could be utilised as research stations to monitor large-scale, long-term experiments in savanna rangeland and gully erosion rehabilitation, using various gully, vegetation, fire, grazing and soil management regimes. These areas could also be conjunctively used for biodiversity improvements, carbon retention, and prevention of weed spread.
Proactive Revegetation Within and Above Alluvial Gullies
- Experimentation into large-scale aerial seeding grass vegetation into alluvial gullies during the wet season with a variety of plant species is needed before catchment-scale programs could be developed to cumulatively address gully erosion.
- The germination and growth success of a wider variety of native and exotic grass should be researched in sodic alluvial soils to determine the most appropriate species for seeding and stabilising gullies. The rooting depths and soil cohesion properties of native and exotic species also is poorly understood in sodic alluvial soils.
- The influence of annual weeds (herbs and grass) on the recovery of native perennial grasses, soil hydrological functions (infiltration, root cohesion, roughness), and accelerated water runoff from river frontage terraces need more research, in relation to downslope alluvial gully erosion.
Cattle Management and Alluvial Gullies
- Large-scale adaptive management research is needed on how to best balance the needs of cattle grazing, perennial grass health and cover, weed control, and fire management, while also reducing alluvial gully erosion on sodic soils and river frontage. Different cattle spelling and rotation regimes should be trailed to maximise vegetative cover in and around alluvial gullies while also supporting a viable cattle industry. Otherwise, cattle grazing pressure will need to be shifted away from large areas sensitive to gully erosion.
- The mechanisms of gully initiation and acceleration from cattle tracks (pads) needs more research. Studies should be conducted on animal migration routes and patterns via tracking, vegetation cover influenced by grazing along tracks, water runoff acceleration along tracks, subtle water flow paths across floodplain flats and hollows, cattle track concentration down pre-existing gully features, and the potential to revegetate and infill existing cattle tracks over time through cattle exclusion.
Fire Regimes and Alluvial Gullies
- Fire regimes research should be conducted to determine what specific fire regimes would be most appropriate to reduce water runoff, soil erosion, and the initiation or acceleration of alluvial gully erosion on river frontage woodlands and grasslands in northern Australia, especially on highly dispersible or sodic soils on alluvial terraces and floodplains. Research on the use of fire for weed control along river frontage terraces is also needed. Sediment erosion and yield should be measured in association with careful fire treatments and control sites.
Physical Control of Alluvial Gullies
- Headcut stabilisation field experiments are needed for controlling young very active headcuts of alluvial gullies using engineered chute and drop structures, especially in dispersible or sodic soils. Their physical- and cost-effectiveness, long-term stability, and geomorphic impacts are unknown for alluvial gullies.
- The use of water diversion berms above long alluvial scarp fronts should be researched and trialled in more detail. Careful consideration is warranted for disturbance of sodic soils, damage to native vegetation, flow paths on subtle topography, designing safe water disposal areas, future scarp retreat, and piping through berms in sodic soils.
- Road field experiments are needed on how to best install, manage and maintain simple dirt roads and tracks in highly dispersible or sodic soils and steep river banks on river frontage in northern Australia, in order to reduce alluvial gully erosion initiation and acceleration. Road research started in this study should be continued to understand longer-term declines in sediment yield from roads treated with preliminary BMP structures and surfacing.
Social-Economic Aspects of Alluvial Gully Control
- The costs and economic viability of alluvial gully erosion control measures needs more detailed research and guidance, with and without government or market-based assistance.
- The market potential for payments for ecosystem services (soil, carbon, biodiversity retention) to reduce alluvial gully erosion should be investigated in detail.
- The economic value of losses of sediment, riparian habitat, biodiversity, and carbon sequestration potential along river frontage needs to be quantified, as well as off-site impacts of alluvial gully erosion on downstream sedimentation, freshwater and marine habitat degradation, and cultural use and values across the landscape.
- The profitability of marginal and degraded grazing lands on Cape York Peninsula needs research attention, along with the economic and social costs of improving water quality by altering land use, and the economic benefits of soil retention to grazing and farm production.