Using geomorphology to assess contour furrowing in western New South Wales, Australia Gresley Wakelin-King A,B A Department of Agricultural Sciences, La Trobe University, Bundoora, Vic. 3086, Australia. B Wakelin Associates, Clifton Hill, Vic. 3068, Australia. Email: gresley@wakelinassociates.com.au Abstract. This study examines landscape rehabilitation treatments installed 20–40 years ago in the Western Catchment of NSW. Treatment outcomes were assessed using geomorphic criteria, because geomorphic processes are fundamental to ecological permanence. Contour furrowing creates artificial runoff-runon sets which intercept runoff (resistance to flow by windrows microrelief and surface roughness) and promote infiltration (artificial permeability by ripping). As originally conceived, after windrows subside, flow resistance would be afforded by surface roughness under belts of vegetation. This study shows that rehabilitation treatments have a more complex relationship with the landscape than this would suggest, and that the final effect of the treatment depends on the geomorphic processes natural to the site. Treatment design should therefore be site-specific. The relevant aspects of treatment design are site location, runoff : runon ratio (expressed as furrow spacing and furrow length), furrow placement, and post-treatment management. Some long-term successes are documented. In ironstone ridge country affected by impermeable hard-setting soils, furrowing creates artificial permeability, allowing plant germination; plant material in the soil reverses hard-setting and establishes self-sustaining permeability. In stony gilgai country furrowing through vegetated patches can aid in re- establishing vegetation, but furrowing through stony runoff patches only diminishes, rather than improves, landscape function. Other landscape types will have different key attributes. In all cases, selection of appropriate sites for rehabilitation treatment is of primary importance. The 1990s NSW Soil Conservation Service best-practice included a specialised furrower, surveying techniques for accurate furrow placement along the contour, staggered gaps along each furrow line to reduce risks of gullying by windrow breakthrough, and post-treatment management of total grazing pressure. New guidelines for treatment design developed from this study include determining for each site the optimum runoff:runon ratio (which varies according to climate, gradient, vegetation, and regolith), and matching furrow spacing and furrow/gap length to local runoff:runon ratios. In stony gilgai country, furrow placement should be along the contour but within non-stony patches; elsewhere, placement should be rigorously along the contour. In ironstone ridge country, a greater runoff:runon ratio, commensurate with the area’s apparently larger patch scale, can be achieved by having more gap than furrow along each furrow line. No single rehabilitation technique will fit all landscape types, and these guidelines will ideally be developed further with investigation of other landscapes. Additional keywords: geomorphology, rehabilitation, furrowing, pitting, rangeland management. Introduction This study reviews the development of furrowing and allied techniques, and investigates the outcomes of treatments undertaken in the Western Catchment of New South Wales (Fig. 1) over a 40 year period. In the range rehabilitation technique contour furrowing, ideally each furrow maintains a steady elevation: it is installed ‘along the contour’ of the land surface. It is part of a spectrum of rehabilitation works which also includes ploughing, ripping, and pitting. These techniques involve breaking the ground surface to create a favourable environment for vegetation, usually within the context of a degraded local landscape. Mechanical treatments for improving rangeland productivity or ameliorating erosion have been undertaken since the early to mid 1900s in the USA and in Australia (Soil Conservation Branch 1 ; Branson et al. 1966; Newman 1966; Cunningham 1967, 1987; Hacker 1989). There has been a long period of formal and informal experimentation of mechanical landscape rehabilitation. With each technique tried, methods evolved, and the expectation of 1 Soil Conservation Branch (Department of Agriculture, South Australia). Re-vegetation by “pitting”. Special Bulletin No. 5.71, Department of Agriculture, Adelaide. Ó Australian Rangeland Society 2011 10.1071/RJ10080 1036-9872/11/020153 CSIRO PUBLISHING www.publish.csiro.au/journals/trj The Rangeland Journal, 2011, 33, 153–171