The experimental catchments range from 71 to 124 ha with at least four smaller microcatchments representing different land uses delineated within. All catchments have slopes ranging from 12 to 80%, and an average annual rainfall ranging from 1,080 to 2,500 mm. In some catchments, water flows in the creeks only during the rainy season. The catchments are dominated by annual cash crops with some patches of perennials and are cultivated primarily by ethnic minorities. In general, the model catchments represent a resource management domain with common biophysical and socioeconomic characteristics as follows:

The soils are generally acid with low inherent fertility that declines rapidly under continuous cultivation without external inputs.

Slopes are steep and soil erosion is the major land degradation process.

The climate is warm, humid or subhumid, and tropical or subtropical. Rainfall intensities in the wet season are generally high.

The native vegetation is commonly rainforest, but large areas have been logged over, subject to shifting cultivation, and covered with pernicious weeds like Imperata cylindrica. The area cultivated every year to subsistence food crops such as rice and maize is increasing (Garrity, 1993).

Steepland areas are remote and have been bypassed by government development schemes.

The shifting cultivators in many areas are ethnic minorities, but increasingly upper catchments are being inhabited by lowland people unable to find land to cultivate elsewhere

Many governments now require the shifting cultivators to abandon their nomadic lives and settle in one place, but lack of land tenure remains a problem.

Off-farm employment through migration to cities and to other countries in the region, is a major source of income (Renaud et al., 1998).