2.2. Field survey
The structure and erosion characteristics of bench
terraces in Pang Prarachatan village were surveyed in
August 2001 and 2003. August is the middle month of the
heavy rainfall season in Thailand, so this makes it easier to
observe soil erosion. The structure of the bench terraces, the
grade of the slope between the bench terraces, the bed
width, and the ground cover of terraces were all investigated.
The erosion characteristics, such as sheetwash, rilling,
and gullying, were evaluated by observation of the terraces.
Fifty-four samples of surface soil (0.01–0.06 m deep) were
taken from the terraces and the physical properties such as
particle size distribution, dry density, and saturated permeability,
and the chemical properties such as nitrogen,
phosphorus, and organic matter content were analysed.
Management practices relating to maintaining the bench
terraces were also investigated.